In rec.autos.tech, on Sat, 03 Apr 2021 02:07:24 -0400, "Steve W."
wrote:

Scott Dorsey wrote:
micky wrote:
In rec.autos.tech, on 27 Mar 2021 19:31:15 -0000,
(Scott Dorsey) wrote:

AK wrote:
I had an oxygen sensor replaced.

Prior to that I got 20 mpg in the city for my CX7.

Now I am getting 21.5 mpg.

Could that increase be due to the replacement of the O2 sensor?
If your O2 sensor was reading low and causing the computer to run the
engine too rich, then yes.
So if now I get codes P0171 and P0174, which means that both banks are
running lean, does that mean replacing the sensors will cause the
opposite of what AK had, richer mixturen and decreased mpg?


Changing the sensors will do nothing but show the same codes again.
Those codes you posted mean the sensors are working. They are seeing
that there is excess oxygen in the exhaust stream compared to what they
expect based on the incoming airflow numbers.
The issue is not them but in the engine. As both are full bank lean
codes I would look at the fuel trims and the O2 live data and check for

I did buy a code reader last year that would read the live data, but
what I should look for has been mostly a mystery since then, until the
video below. I found it a few days ago but just had time to watch it.

Cars are much more complicated than when I was a boy, or even a
teenager, and I've said for years and told quite a few people that
anyone smart enough to be a good mechanic these days could succeed in a
lot of fields.

vacuum leaks or an intake leak that is letting in unmetered air.
As you don't post any P0300 range codes I doubt it's fuel pressure as
that will commonly set misfire codes as well as the lean codes.

Thanks. I found a long video that went over at least some of the
things to do with a P0171. https://www.youtube.com/watch?v=SugtR4KMIDU

He ended up finding a leaky brake booster and a somewhat bad MAF sensor,
but more importantly he goes into some detail about what everything
means.

You and some of the other people here know everything that is in this
video. I miss the days when there were people here who knew less than I
do. They woudl benefit more from this post than you or the others here
will.

micky wrote:
In rec.autos.tech, on Sat, 03 Apr 2021 02:07:24 -0400, "Steve W."
wrote:

Scott Dorsey wrote:
micky wrote:
In rec.autos.tech, on 27 Mar 2021 19:31:15 -0000,
(Scott Dorsey) wrote:

AK wrote:
I had an oxygen sensor replaced.

Prior to that I got 20 mpg in the city for my CX7.

Now I am getting 21.5 mpg.

Could that increase be due to the replacement of the O2 sensor?
If your O2 sensor was reading low and causing the computer to run the
engine too rich, then yes.
So if now I get codes P0171 and P0174, which means that both banks are
running lean, does that mean replacing the sensors will cause the
opposite of what AK had, richer mixturen and decreased mpg?

Changing the sensors will do nothing but show the same codes again.
Those codes you posted mean the sensors are working. They are seeing
that there is excess oxygen in the exhaust stream compared to what they
expect based on the incoming airflow numbers.
The issue is not them but in the engine. As both are full bank lean
codes I would look at the fuel trims and the O2 live data and check for

I did buy a code reader last year that would read the live data, but
what I should look for has been mostly a mystery since then, until the
video below. I found it a few days ago but just had time to watch it.

Cars are much more complicated than when I was a boy, or even a
teenager, and I've said for years and told quite a few people that
anyone smart enough to be a good mechanic these days could succeed in a
lot of fields.

vacuum leaks or an intake leak that is letting in unmetered air.
As you don't post any P0300 range codes I doubt it's fuel pressure as
that will commonly set misfire codes as well as the lean codes.

Thanks. I found a long video that went over at least some of the
things to do with a P0171. https://www.youtube.com/watch?v=SugtR4KMIDU

He ended up finding a leaky brake booster and a somewhat bad MAF sensor,
but more importantly he goes into some detail about what everything
means.

You and some of the other people here know everything that is in this
video. I miss the days when there were people here who knew less than I
do. They woudl benefit more from this post than you or the others here
will.

I don't know everything but I'm pretty good at diagnostic and repair
work on vehicles.

How much do you really want to know about modern engine diagnostics?

--
Steve W.

Steve W. wrote:
micky wrote:
In rec.autos.tech, on Sat, 03 Apr 2021 02:07:24 -0400, "Steve W."
wrote:

Scott Dorsey wrote:
micky wrote:
In rec.autos.tech, on 27 Mar 2021 19:31:15 -0000,
(Scott Dorsey) wrote:

AK wrote:
I had an oxygen sensor replaced.

Prior to that I got 20 mpg in the city for my CX7.

Now I am getting 21.5 mpg.

Could that increase be due to the replacement of the O2 sensor?
If your O2 sensor was reading low and causing the computer to run the
engine too rich, then yes.
So if now I get codes P0171 and P0174, which means that both banks are
running lean, does that mean replacing the sensors will cause the
opposite of what AK had, richer mixturen and decreased mpg?
Changing the sensors will do nothing but show the same codes again.
Those codes you posted mean the sensors are working. They are seeing
that there is excess oxygen in the exhaust stream compared to what they
expect based on the incoming airflow numbers.
The issue is not them but in the engine. As both are full bank lean
codes I would look at the fuel trims and the O2 live data and check for
I did buy a code reader last year that would read the live data, but
what I should look for has been mostly a mystery since then, until the
video below. I found it a few days ago but just had time to watch it.

Cars are much more complicated than when I was a boy, or even a
teenager, and I've said for years and told quite a few people that
anyone smart enough to be a good mechanic these days could succeed in a
lot of fields.

vacuum leaks or an intake leak that is letting in unmetered air.
As you don't post any P0300 range codes I doubt it's fuel pressure as
that will commonly set misfire codes as well as the lean codes.
Thanks. I found a long video that went over at least some of the
things to do with a P0171. https://www.youtube.com/watch?v=SugtR4KMIDU

He ended up finding a leaky brake booster and a somewhat bad MAF sensor,
but more importantly he goes into some detail about what everything
means.

You and some of the other people here know everything that is in this
video. I miss the days when there were people here who knew less than I
do. They woudl benefit more from this post than you or the others here
will.

I don't know everything but I'm pretty good at diagnostic and repair
work on vehicles.

How much do you really want to know about modern engine diagnostics?

Oh where he is checking the hoses, a quick trick is to use carb cleaner
and spray it around the hoses. If the engine rpm suddenly jumps look in
the area you were spraying for a leak.

--
Steve W.

In alt.home.repair, on Wed, 07 Apr 2021 20:24:26 -0400, "Steve W."
wrote:

Steve W. wrote:
micky wrote:
In rec.autos.tech, on Sat, 03 Apr 2021 02:07:24 -0400, "Steve W."
wrote:

Scott Dorsey wrote:
micky wrote:
In rec.autos.tech, on 27 Mar 2021 19:31:15 -0000,
(Scott Dorsey) wrote:

AK wrote:
I had an oxygen sensor replaced.

Prior to that I got 20 mpg in the city for my CX7.

Now I am getting 21.5 mpg.

Could that increase be due to the replacement of the O2 sensor?
If your O2 sensor was reading low and causing the computer to run the
engine too rich, then yes.
So if now I get codes P0171 and P0174, which means that both banks are
running lean, does that mean replacing the sensors will cause the
opposite of what AK had, richer mixturen and decreased mpg?

Changing the sensors will do nothing but show the same codes again.
Those codes you posted mean the sensors are working. They are seeing
that there is excess oxygen in the exhaust stream compared to what they
expect based on the incoming airflow numbers.
The issue is not them but in the engine. As both are full bank lean
codes I would look at the fuel trims and the O2 live data and check for

I did buy a code reader last year that would read the live data, but
what I should look for has been mostly a mystery since then, until the
video below. I found it a few days ago but just had time to watch it.

Cars are much more complicated than when I was a boy, or even a
teenager, and I've said for years and told quite a few people that
anyone smart enough to be a good mechanic these days could succeed in a
lot of fields.

vacuum leaks or an intake leak that is letting in unmetered air.
As you don't post any P0300 range codes I doubt it's fuel pressure as
that will commonly set misfire codes as well as the lean codes.

Thanks. I found a long video that went over at least some of the
things to do with a P0171. https://www.youtube.com/watch?v=SugtR4KMIDU

I made a lot notes based on what he said.

He ended up finding a leaky brake booster and a somewhat bad MAF sensor,
but more importantly he goes into some detail about what everything
means.

You and some of the other people here know everything that is in this
video. I miss the days when there were people here who knew less than I
do. They would benefit more from this post than you or the others here
will.

I don't know everything but I'm pretty good at diagnostic and repair
work on vehicles.

How much do you really want to know about modern engine diagnostics?

Just enough to fix my car, and maybe a little more. :-)

I used the scanner today and the short and long term trims tracked the
results of the guy who made the video, at idle and up to 2500rpm. Also
the MAF value (in metric) and the ECT, Spark, Load, and IAT seemed on
track. Mine starts at OL and goes quickly to CL for both banks.

I forgot to look at the 02BnSn, but I think they're stored in the
scanner. Yes, I posted them below, if that's what Review refers to.

The scanner is inside with me, but the notes are in the car. I'll post
them here later.

Oh where he is checking the hoses, a quick trick is to use carb cleaner
and spray it around the hoses. If the engine rpm suddenly jumps look in
the area you were spraying for a leak.

He sprayed with water, hoping to hear a hiss, but not with carb clean.

I was going to spray with brake cleaner, because it says No Residue, but
maybe carb cleaner is better? (He didn't say why not, not a word about
spraying with other things.)

If that doesn't find it (and I did look everywhere I could think of last
year, using propane), I'm going to disconnect the purge solenoid and
plug that hose, and then disconnect the brake booster and plug that one,
the hoses that go into the throttle body. That's how he found a major
problem with his brake booster.

He used a vacuum tester to plug each hose in turn that goes to the
throttle body, but seems to me I don't need a tester. I can assume
there is some vacuum if the engine is running and it doesn't matter how
much, and all I need to do is use a pencil or something bigger to plug
each hose.

Last time when I was trying to find a vacuum leak, I didn't know and
didn't think about the fact that some leaks don't go to the outside,
like a leak in a hose does. He didn't name anything other than the
cannister circuit** and the brake booster that could have an internal
vacuum leak. There are so many hoses, I dont' have much confidence I
would think of something else even if it exists. Are there other things
I should disconnect? **The cannister circuit of couree includes a
long hose almost to the gas tank, which he couldn't feel or spray or
look at.

Fixing the brake booster lowered his trim total by 30 points but it was
still too high. He found that his MAF sensor was off somewhat and after
he replaced that too, everything was good. (Trim total was between +10
and -10.) I replaced my MAF sensor about 10,000 miles ago, on the hope
that would fix things. I only used a mimimal code reader th1en so if it
made any difference, I don't know, but it didn't get rid of the codes
and, I doubt if it's the problem now. AND today, I don't want to guess
what my MAF was at idle, but I know it was 9.5 at 2500RPM. His original
one started at idle (cold) 0.57 to idle (warm) 1.84, g/sec (and he said
2 to 3 would be better), but even at 2500 rpm, his value would never go
over 7 or 8, so I think mine works better. At least I think so.



I'm not sure what I see when I go to Review / Live Data / Location #1
(the only one listed). IIUC, the data there is from this afternooon and
it says

DTC_CNT is 2. That makes sense, P0171 and P0174.

02B1S2(v) is 0.680
B2 is 0.680 also
O2B1S1 is 3.279
02B2S1 is 3.250 very similar to bank 1
He had said that 3.3 is perfect 14.7 to 1, air to fuel ratio. My
two numbers are pretty close but maybe they'd be closer to 3.3 if ...


EQ_RATB2S1 is 0.988 but I don't know what that means and he didn't say,
and I havent' taken the time to look it up yet.
B1S1 is 1.006, very similar.

SHRTFTB1S2 is N/A.
while
SHRTFTB2S2 is 99.2 Isn't that strange? In the 4 values 8 lines up,
B1S2 and B2S2 are exactly the same. there something wrong with B1S2?

02SLOC is B1S12--B2S12-- whatever that means.


I hope I didn't give too much info.

In alt.home.repair, on Wed, 07 Apr 2021 21:50:11 -0400, micky
wrote:

In alt.home.repair, on Wed, 07 Apr 2021 20:24:26 -0400, "Steve W."
wrote:

Steve W. wrote:
micky wrote:
In rec.autos.tech, on Sat, 03 Apr 2021 02:07:24 -0400, "Steve W."
wrote:

Scott Dorsey wrote:
micky wrote:
In rec.autos.tech, on 27 Mar 2021 19:31:15 -0000,
(Scott Dorsey) wrote:

AK wrote:
I had an oxygen sensor replaced.

Prior to that I got 20 mpg in the city for my CX7.

Now I am getting 21.5 mpg.

Could that increase be due to the replacement of the O2 sensor?
If your O2 sensor was reading low and causing the computer to run the
engine too rich, then yes.
So if now I get codes P0171 and P0174, which means that both banks are
running lean, does that mean replacing the sensors will cause the
opposite of what AK had, richer mixturen and decreased mpg?

Changing the sensors will do nothing but show the same codes again.
Those codes you posted mean the sensors are working. They are seeing
that there is excess oxygen in the exhaust stream compared to what they
expect based on the incoming airflow numbers.
The issue is not them but in the engine. As both are full bank lean
codes I would look at the fuel trims and the O2 live data and check for

I did buy a code reader last year that would read the live data, but
what I should look for has been mostly a mystery since then, until the
video below. I found it a few days ago but just had time to watch it.

Cars are much more complicated than when I was a boy, or even a
teenager, and I've said for years and told quite a few people that
anyone smart enough to be a good mechanic these days could succeed in a
lot of fields.

vacuum leaks or an intake leak that is letting in unmetered air.
As you don't post any P0300 range codes I doubt it's fuel pressure as
that will commonly set misfire codes as well as the lean codes.

Thanks. I found a long video that went over at least some of the
things to do with a P0171. https://www.youtube.com/watch?v=SugtR4KMIDU

I made a lot notes based on what he said.

He ended up finding a leaky brake booster and a somewhat bad MAF sensor,
but more importantly he goes into some detail about what everything
means.

You and some of the other people here know everything that is in this
video. I miss the days when there were people here who knew less than I
do. They would benefit more from this post than you or the others here
will.

I don't know everything but I'm pretty good at diagnostic and repair
work on vehicles.

How much do you really want to know about modern engine diagnostics?

Just enough to fix my car, and maybe a little more. :-)

I used the scanner today and the short and long term trims tracked the
results of the guy who made the video, at idle and up to 2500rpm. Also

An important thing I left out was that he said "When we raise RPM to
2000, does SHRT get better, or worse, or the same? If it gets better,
lower, usually a vacuum leak."

It got lower for him. And for me, it went up a little at first but then
went down somewhere between quite a bit and a lot. Numbers, if any, are
in the car.

More than one value I saw go in two different directions, and in other
aspects of my life, a little bit in one direction at first and much more
in the other direction soon after. I think he mentioned that too.

So so far it's looking like a vacuum leak.

Maybe no need to replace either 02 sensor, especially the one behind
the engine. OTOH, I've read that they fail with age or miles. 70,000,
100,000 were mentioned and I have 140,000.




the MAF value (in metric) and the ECT, Spark, Load, and IAT seemed on
track. Mine starts at OL and goes quickly to CL for both banks.

I forgot to look at the 02BnSn, but I think they're stored in the
scanner. Yes, I posted them below, if that's what Review refers to.

The scanner is inside with me, but the notes are in the car. I'll post
them here later.

Oh where he is checking the hoses, a quick trick is to use carb cleaner
and spray it around the hoses. If the engine rpm suddenly jumps look in
the area you were spraying for a leak.

He sprayed with water, hoping to hear a hiss, but not with carb clean.

I was going to spray with brake cleaner, because it says No Residue, but
maybe carb cleaner is better? (He didn't say why not, not a word about
spraying with other things.)

If that doesn't find it (and I did look everywhere I could think of last
year, using propane), I'm going to disconnect the purge solenoid and
plug that hose, and then disconnect the brake booster and plug that one,
the hoses that go into the throttle body. That's how he found a major
problem with his brake booster.

He used a vacuum tester to plug each hose in turn that goes to the
throttle body, but seems to me I don't need a tester. I can assume
there is some vacuum if the engine is running and it doesn't matter how
much, and all I need to do is use a pencil or something bigger to plug
each hose.

Last time when I was trying to find a vacuum leak, I didn't know and
didn't think about the fact that some leaks don't go to the outside,
like a leak in a hose does. He didn't name anything other than the
cannister circuit** and the brake booster that could have an internal
vacuum leak. There are so many hoses, I dont' have much confidence I
would think of something else even if it exists. Are there other things
I should disconnect? **The cannister circuit of couree includes a
long hose almost to the gas tank, which he couldn't feel or spray or
look at.

Fixing the brake booster lowered his trim total by 30 points but it was
still too high. He found that his MAF sensor was off somewhat and after
he replaced that too, everything was good. (Trim total was between +10
and -10.) I replaced my MAF sensor about 10,000 miles ago, on the hope
that would fix things. I only used a mimimal code reader th1en so if it
made any difference, I don't know, but it didn't get rid of the codes
and, I doubt if it's the problem now. AND today, I don't want to guess
what my MAF was at idle, but I know it was 9.5 at 2500RPM. His original
one started at idle (cold) 0.57 to idle (warm) 1.84, g/sec (and he said
2 to 3 would be better), but even at 2500 rpm, his value would never go
over 7 or 8, so I think mine works better. At least I think so.



I'm not sure what I see when I go to Review / Live Data / Location #1
(the only one listed). IIUC, the data there is from this afternooon and
it says

DTC_CNT is 2. That makes sense, P0171 and P0174.

02B1S2(v) is 0.680
B2 is 0.680 also
O2B1S1 is 3.279
02B2S1 is 3.250 very similar to bank 1
He had said that 3.3 is perfect 14.7 to 1, air to fuel ratio. My
two numbers are pretty close but maybe they'd be closer to 3.3 if ...


EQ_RATB2S1 is 0.988 but I don't know what that means and he didn't say,
and I havent' taken the time to look it up yet.
B1S1 is 1.006, very similar.

SHRTFTB1S2 is N/A.
while
SHRTFTB2S2 is 99.2 Isn't that strange? In the 4 values 8 lines up,
B1S2 and B2S2 are exactly the same. there something wrong with B1S2?

02SLOC is B1S12--B2S12-- whatever that means.


I hope I didn't give too much info.

In alt.home.repair, on Wed, 07 Apr 2021 22:30:04 -0400, micky
wrote:


I used the scanner today and the short and long term trims tracked the
results of the guy who made the video, at idle and up to 2500rpm. Also

An important thing I left out was that he said "When we raise RPM to
2000, does SHRT [short term trim] get better, or worse, or the same? If it gets better,
lower, usually a vacuum leak."

And he said in the video, "If it's worse or the same, it's probably a
fuel delivery or Mass Air flow problem."



It got lower for him. And for me, it went up a little at first but then
went down somewhere between quite a bit and a lot. Numbers, if any, are
in the car.

More than one value I saw go in two different directions, and in other
aspects of my life, a little bit in one direction at first and much more
in the other direction soon after. I think he mentioned that too.

So so far it's looking like a vacuum leak.

Maybe no need to replace either 02 sensor, especially the one behind
the engine. OTOH, I've read that they fail with age or miles. 70,000,
100,000 were mentioned and I have 140,000.

Steve W. wrote:
Steve W. wrote:
micky wrote:
In rec.autos.tech, on Sat, 03 Apr 2021 02:07:24 -0400, "Steve W."
wrote:

Scott Dorsey wrote:
micky wrote:
In rec.autos.tech, on 27 Mar 2021 19:31:15 -0000,
(Scott Dorsey) wrote:

AK wrote:
I had an oxygen sensor replaced.

Prior to that I got 20 mpg in the city for my CX7.

Now I am getting 21.5 mpg.

Could that increase be due to the replacement of the O2 sensor?
If your O2 sensor was reading low and causing the computer to run the
engine too rich, then yes.
So if now I get codes P0171 and P0174, which means that both banks are
running lean, does that mean replacing the sensors will cause the
opposite of what AK had, richer mixturen and decreased mpg?
Changing the sensors will do nothing but show the same codes again.
Those codes you posted mean the sensors are working. They are seeing
that there is excess oxygen in the exhaust stream compared to what they
expect based on the incoming airflow numbers.
The issue is not them but in the engine. As both are full bank lean
codes I would look at the fuel trims and the O2 live data and check for
I did buy a code reader last year that would read the live data, but
what I should look for has been mostly a mystery since then, until the
video below. I found it a few days ago but just had time to watch it.

Cars are much more complicated than when I was a boy, or even a
teenager, and I've said for years and told quite a few people that
anyone smart enough to be a good mechanic these days could succeed in a
lot of fields.

vacuum leaks or an intake leak that is letting in unmetered air.
As you don't post any P0300 range codes I doubt it's fuel pressure as
that will commonly set misfire codes as well as the lean codes.
Thanks. I found a long video that went over at least some of the
things to do with a P0171. https://www.youtube.com/watch?v=SugtR4KMIDU

He ended up finding a leaky brake booster and a somewhat bad MAF sensor,
but more importantly he goes into some detail about what everything
means.

You and some of the other people here know everything that is in this
video. I miss the days when there were people here who knew less than I
do. They woudl benefit more from this post than you or the others here
will.
I don't know everything but I'm pretty good at diagnostic and repair
work on vehicles.

How much do you really want to know about modern engine diagnostics?

Oh where he is checking the hoses, a quick trick is to use carb cleaner
and spray it around the hoses. If the engine rpm suddenly jumps look in
the area you were spraying for a leak.


From what you posted you have a vacuum leak/pirate air issue as the
primary problem. You can use brake clean or carb cleaner, they are both
more or less paint thinners that burn ok. I use carb cleaner because the
older version of brake cleaner is chlorinated and generates toxic gas
when burned.
The thing to remember though is that in the video he is working on a car
different than yours, some things apply, others don't. For instance MAF
flow, as engine sizes go up, MAF numbers increase even at idle to feed
the larger engine.
Try this
https://support.alldata.com/sites/ma...ing_110918.pdf

Looking at the fuel trims that go up, then start coming down means that
it's a medium sized leak. As the throttle opens it goes past the point
where the pirate air is the main component and the mixture improves. If
it started improving immediately it would be a small leak.

For the sensor data you want to look at it live, and watch what it
actually reads, if the front sensors are changing voltages rapidly as
the engine runs and the rear sensors stay at a somewhat constant number
and don't vary like the fronts, the sensors are working and although
they may be worn, they are doing their job and the converters are working.
You may be surprised at where a vacuum leak can be, brake booster, PCV
system, intake manifold gaskets, a damaged port on the manifold, in the
EVAP system and a host of others, some external others internal.
OH the wuse of water for leaks is somewhat common, it's because you can
use it on a hot or cold engine or one where you have ignition sources
like open plug wires or bad coils. The amount of cleaner you will use
won't be an issue though, just be sure to start on a cold engine.
Usually something like an intake leak will get better as the engine
warms up so you want to catch it when it's cold.


--
Steve W.

On Thursday, April 8, 2021 at 2:05:17 AM UTC-4, Steve W. wrote:
Steve W. wrote:
Steve W. wrote:
micky wrote:
In rec.autos.tech, on Sat, 03 Apr 2021 02:07:24 -0400, "Steve W."
wrote:

Scott Dorsey wrote:
micky wrote:
In rec.autos.tech, on 27 Mar 2021 19:31:15 -0000,
(Scott Dorsey) wrote:

AK wrote:
I had an oxygen sensor replaced.

Prior to that I got 20 mpg in the city for my CX7.

Now I am getting 21.5 mpg.

Could that increase be due to the replacement of the O2 sensor?
If your O2 sensor was reading low and causing the computer to run the
engine too rich, then yes.
So if now I get codes P0171 and P0174, which means that both banks are
running lean, does that mean replacing the sensors will cause the
opposite of what AK had, richer mixturen and decreased mpg?
Changing the sensors will do nothing but show the same codes again.
Those codes you posted mean the sensors are working. They are seeing
that there is excess oxygen in the exhaust stream compared to what they
expect based on the incoming airflow numbers.
The issue is not them but in the engine. As both are full bank lean
codes I would look at the fuel trims and the O2 live data and check for
I did buy a code reader last year that would read the live data, but
what I should look for has been mostly a mystery since then, until the
video below. I found it a few days ago but just had time to watch it.

Cars are much more complicated than when I was a boy, or even a
teenager, and I've said for years and told quite a few people that
anyone smart enough to be a good mechanic these days could succeed in a
lot of fields.

vacuum leaks or an intake leak that is letting in unmetered air.
As you don't post any P0300 range codes I doubt it's fuel pressure as
that will commonly set misfire codes as well as the lean codes.
Thanks. I found a long video that went over at least some of the
things to do with a P0171. https://www.youtube.com/watch?v=SugtR4KMIDU

He ended up finding a leaky brake booster and a somewhat bad MAF sensor,
but more importantly he goes into some detail about what everything
means.

You and some of the other people here know everything that is in this
video. I miss the days when there were people here who knew less than I
do. They woudl benefit more from this post than you or the others here
will.
I don't know everything but I'm pretty good at diagnostic and repair
work on vehicles.

How much do you really want to know about modern engine diagnostics?

Oh where he is checking the hoses, a quick trick is to use carb cleaner
and spray it around the hoses. If the engine rpm suddenly jumps look in
the area you were spraying for a leak.

From what you posted you have a vacuum leak/pirate air issue as the
primary problem. You can use brake clean or carb cleaner, they are both
more or less paint thinners that burn ok. I use carb cleaner because the
older version of brake cleaner is chlorinated and generates toxic gas
when burned.
The thing to remember though is that in the video he is working on a car
different than yours, some things apply, others don't. For instance MAF
flow, as engine sizes go up, MAF numbers increase even at idle to feed
the larger engine.
Try this
https://support.alldata.com/sites/ma...ing_110918.pdf

Looking at the fuel trims that go up, then start coming down means that
it's a medium sized leak. As the throttle opens it goes past the point
where the pirate air is the main component and the mixture improves. If
it started improving immediately it would be a small leak.

For the sensor data you want to look at it live, and watch what it
actually reads, if the front sensors are changing voltages rapidly the engine runs and the rear sensors stay at a somewhat constant number
and don't vary like the fronts, the sensors are working and although
they may be worn, they are doing their job and the converters are working.
You may be surprised at where a vacuum leak can be, brake booster, PCV
system, intake manifold gaskets, a damaged port on the manifold, in the
EVAP system and a host of others, some external others internal.
OH the wuse of water for leaks is somewhat common, it's because you can
use it on a hot or cold engine or one where you have ignition sources
like open plug wires or bad coils. The amount of cleaner you will use
won't be an issue though, just be sure to start on a cold engine.
Usually something like an intake leak will get better as the engine
warms up so you want to catch it when it's cold.


--
Steve W.

Since he's fiddled around looking for a vacuum leak for awhile already and can't
find an obvious one, I'd suggest getting a schematic that shows all the vacuum lines.
Then it will be easier to figure out where they tap off from, how to separate that
section and plug it. Or try the smoke tester. I've never used one, but have read of
other people using them and sounds like in principle it would work.

On Thu, 08 Apr 2021 02:05:14 -0400, "Steve W."
wrote:

Steve W. wrote:
Steve W. wrote:
micky wrote:
In rec.autos.tech, on Sat, 03 Apr 2021 02:07:24 -0400, "Steve W."
wrote:

Scott Dorsey wrote:
micky wrote:
In rec.autos.tech, on 27 Mar 2021 19:31:15 -0000,
(Scott Dorsey) wrote:

AK wrote:
I had an oxygen sensor replaced.

Prior to that I got 20 mpg in the city for my CX7.

Now I am getting 21.5 mpg.

Could that increase be due to the replacement of the O2 sensor?
If your O2 sensor was reading low and causing the computer to run the
engine too rich, then yes.
So if now I get codes P0171 and P0174, which means that both banks are
running lean, does that mean replacing the sensors will cause the
opposite of what AK had, richer mixturen and decreased mpg?
Changing the sensors will do nothing but show the same codes again.
Those codes you posted mean the sensors are working. They are seeing
that there is excess oxygen in the exhaust stream compared to what they
expect based on the incoming airflow numbers.
The issue is not them but in the engine. As both are full bank lean
codes I would look at the fuel trims and the O2 live data and check for
I did buy a code reader last year that would read the live data, but
what I should look for has been mostly a mystery since then, until the
video below. I found it a few days ago but just had time to watch it.

Cars are much more complicated than when I was a boy, or even a
teenager, and I've said for years and told quite a few people that
anyone smart enough to be a good mechanic these days could succeed in a
lot of fields.

vacuum leaks or an intake leak that is letting in unmetered air.
As you don't post any P0300 range codes I doubt it's fuel pressure as
that will commonly set misfire codes as well as the lean codes.
Thanks. I found a long video that went over at least some of the
things to do with a P0171. https://www.youtube.com/watch?v=SugtR4KMIDU

He ended up finding a leaky brake booster and a somewhat bad MAF sensor,
but more importantly he goes into some detail about what everything
means.

You and some of the other people here know everything that is in this
video. I miss the days when there were people here who knew less than I
do. They woudl benefit more from this post than you or the others here
will.
I don't know everything but I'm pretty good at diagnostic and repair
work on vehicles.

How much do you really want to know about modern engine diagnostics?

Oh where he is checking the hoses, a quick trick is to use carb cleaner
and spray it around the hoses. If the engine rpm suddenly jumps look in
the area you were spraying for a leak.


From what you posted you have a vacuum leak/pirate air issue as the
primary problem. You can use brake clean or carb cleaner, they are both
more or less paint thinners that burn ok. I use carb cleaner because the
older version of brake cleaner is chlorinated and generates toxic gas
when burned.
The thing to remember though is that in the video he is working on a car
different than yours, some things apply, others don't. For instance MAF
flow, as engine sizes go up, MAF numbers increase even at idle to feed
the larger engine.
Try this
https://support.alldata.com/sites/ma...ing_110918.pdf

Looking at the fuel trims that go up, then start coming down means that
it's a medium sized leak. As the throttle opens it goes past the point
where the pirate air is the main component and the mixture improves. If
it started improving immediately it would be a small leak.

For the sensor data you want to look at it live, and watch what it
actually reads, if the front sensors are changing voltages rapidly as
the engine runs and the rear sensors stay at a somewhat constant number
and don't vary like the fronts, the sensors are working and although
they may be worn, they are doing their job and the converters are working.
You may be surprised at where a vacuum leak can be, brake booster, PCV
system, intake manifold gaskets, a damaged port on the manifold, in the
EVAP system and a host of others, some external others internal.
OH the wuse of water for leaks is somewhat common, it's because you can
use it on a hot or cold engine or one where you have ignition sources
like open plug wires or bad coils. The amount of cleaner you will use
won't be an issue though, just be sure to start on a cold engine.
Usually something like an intake leak will get better as the engine
warms up so you want to catch it when it's cold.
Even something STOOPID like the dipstick not sealed.

In alt.home.repair, on Thu, 8 Apr 2021 06:37:51 -0700 (PDT), trader_4
wrote:

On Thursday, April 8, 2021 at 2:05:17 AM UTC-4, Steve W. wrote:
Steve W. wrote:
Steve W. wrote:
micky wrote:
In rec.autos.tech, on Sat, 03 Apr 2021 02:07:24 -0400, "Steve W."
wrote:

Scott Dorsey wrote:
micky wrote:
In rec.autos.tech, on 27 Mar 2021 19:31:15 -0000,
(Scott Dorsey) wrote:

AK wrote:
I had an oxygen sensor replaced.

Prior to that I got 20 mpg in the city for my CX7.

Now I am getting 21.5 mpg.

Could that increase be due to the replacement of the O2 sensor?
If your O2 sensor was reading low and causing the computer to run the
engine too rich, then yes.
So if now I get codes P0171 and P0174, which means that both banks are
running lean, does that mean replacing the sensors will cause the
opposite of what AK had, richer mixturen and decreased mpg?
Changing the sensors will do nothing but show the same codes again.
Those codes you posted mean the sensors are working. They are seeing
that there is excess oxygen in the exhaust stream compared to what they
expect based on the incoming airflow numbers.
The issue is not them but in the engine. As both are full bank lean
codes I would look at the fuel trims and the O2 live data and check for
I did buy a code reader last year that would read the live data, but
what I should look for has been mostly a mystery since then, until the
video below. I found it a few days ago but just had time to watch it.

Cars are much more complicated than when I was a boy, or even a
teenager, and I've said for years and told quite a few people that
anyone smart enough to be a good mechanic these days could succeed in a
lot of fields.

vacuum leaks or an intake leak that is letting in unmetered air.
As you don't post any P0300 range codes I doubt it's fuel pressure as
that will commonly set misfire codes as well as the lean codes.
Thanks. I found a long video that went over at least some of the
things to do with a P0171. https://www.youtube.com/watch?v=SugtR4KMIDU

He ended up finding a leaky brake booster and a somewhat bad MAF sensor,
but more importantly he goes into some detail about what everything
means.

You and some of the other people here know everything that is in this
video. I miss the days when there were people here who knew less than I
do. They woudl benefit more from this post than you or the others here
will.
I don't know everything but I'm pretty good at diagnostic and repair
work on vehicles.

How much do you really want to know about modern engine diagnostics?

Oh where he is checking the hoses, a quick trick is to use carb cleaner
and spray it around the hoses. If the engine rpm suddenly jumps look in
the area you were spraying for a leak.

From what you posted you have a vacuum leak/pirate air issue as the
primary problem. You can use brake clean or carb cleaner, they are both
more or less paint thinners that burn ok. I use carb cleaner because the
older version of brake cleaner is chlorinated and generates toxic gas
when burned.
The thing to remember though is that in the video he is working on a car
different than yours, some things apply, others don't. For instance MAF
flow, as engine sizes go up, MAF numbers increase even at idle to feed
the larger engine.
Try this
https://support.alldata.com/sites/ma...ing_110918.pdf

Looking at the fuel trims that go up, then start coming down means that
it's a medium sized leak. As the throttle opens it goes past the point
where the pirate air is the main component and the mixture improves. If
it started improving immediately it would be a small leak.

For the sensor data you want to look at it live, and watch what it
actually reads, if the front sensors are changing voltages rapidly the engine runs and the rear sensors stay at a somewhat constant number
and don't vary like the fronts, the sensors are working and although
they may be worn, they are doing their job and the converters are working.
You may be surprised at where a vacuum leak can be, brake booster, PCV
system, intake manifold gaskets, a damaged port on the manifold, in the
EVAP system and a host of others, some external others internal.
OH the wuse of water for leaks is somewhat common, it's because you can
use it on a hot or cold engine or one where you have ignition sources
like open plug wires or bad coils. The amount of cleaner you will use
won't be an issue though, just be sure to start on a cold engine.
Usually something like an intake leak will get better as the engine
warms up so you want to catch it when it's cold.


--
Steve W.

Since he's fiddled around looking for a vacuum leak for awhile already and can't
find an obvious one, I'd suggest getting a schematic that shows all the vacuum lines.

Under the hood is a partial schematic, of thoze hoses related to air
pollution. It doesn't include the brake booster, for example, becauae
I guess that has no effect on air pollution (except when the diaphragm
is broken and they don't count that! Because they only cover what the
law makes them cover.)

It also shows 4 vacuum switching valves, and so far I've only found 3 of
them. But this morning I disconnected the one connected to EVAP,
plugged the tube on the throttle body and it made no change at all in
the fuel trim. I also then disconnected the power brake booster,
plugged the tube, and it made no change in the fuel trim.


This one is very similar to the schematic for my car:
https://www.camryforums.com/forum/at...g-vachose3.jpg
You can click when the cursor ends in + and enlarge the photo.

Can anyone tell me what the rectangle with two hoses ocming out of it
is? It's above the MZ in 1MZ-FE at the bottom left of the picture. And
above the Vacuum Switching Valve that is above that. This part of my car
looks just like this. That is, there is a second VSV, what they label
the PWM Vacuum Switching Valve to the right of that white rectangle (and
if that were bad, they sell a replacement, from Toyota even.)

But the black-outlined white rectangle is just a silver box with two
hoses attached. And two screws holding it to the bracket above the fuel
rail. What does it do?

Then it will be easier to figure out where they tap off from, how to separate that
section and plug it.

There are two more hoses connected to the throttle body, neither as easy
to get off. Neither shown to in the diagram they provide. ONe just
goes to the forward valve cover, and iiuc it coudln't be the problem.
The other comes from a 90^ bent tube and I can't tell where it goes. Too
many things in the way.

I'll try to find more stuff about the 3.3L engine. I have the shop
manual for the 3.0L engine from 2000, but those 0.3 liters etc. make a
big difference.

Or try the smoke tester.

I think we talked about this last year, but I was not despairing yet.
They have one for sale for 100, another for 120, and one for 900. WRT
rental, autozone and advance don't have it, but there was a PepBoys
page, so I called the local Pepboys and he knew almost nothing about it.
I called maybe a bigger Pepboys and he didnt' either but he asked
someone and indded they have such a machine. He didn't even know how
much it costs, but the web page said $30. Well worth it if it works. I
hope they have someone there who stills knows how to use it. And they
want two hours. Maybe more. I guess I can just go and keep busy.


I've never used one, but have read of
other people using them and sounds like in principle it would work.

Yes, it does.

In rec.autos.tech, on Thu, 08 Apr 2021 02:05:14 -0400, "Steve W."
wrote:

Steve W. wrote:
Steve W. wrote:
micky wrote:
In rec.autos.tech, on Sat, 03 Apr 2021 02:07:24 -0400, "Steve W."
wrote:

Scott Dorsey wrote:
micky wrote:
In rec.autos.tech, on 27 Mar 2021 19:31:15 -0000,
(Scott Dorsey) wrote:

AK wrote:
I had an oxygen sensor replaced.

Prior to that I got 20 mpg in the city for my CX7.

Now I am getting 21.5 mpg.

Could that increase be due to the replacement of the O2 sensor?
If your O2 sensor was reading low and causing the computer to run the
engine too rich, then yes.
So if now I get codes P0171 and P0174, which means that both banks are
running lean, does that mean replacing the sensors will cause the
opposite of what AK had, richer mixturen and decreased mpg?
Changing the sensors will do nothing but show the same codes again.
Those codes you posted mean the sensors are working. They are seeing
that there is excess oxygen in the exhaust stream compared to what they
expect based on the incoming airflow numbers.
The issue is not them but in the engine. As both are full bank lean
codes I would look at the fuel trims and the O2 live data and check for
I did buy a code reader last year that would read the live data, but
what I should look for has been mostly a mystery since then, until the
video below. I found it a few days ago but just had time to watch it.

Cars are much more complicated than when I was a boy, or even a
teenager, and I've said for years and told quite a few people that
anyone smart enough to be a good mechanic these days could succeed in a
lot of fields.

vacuum leaks or an intake leak that is letting in unmetered air.
As you don't post any P0300 range codes I doubt it's fuel pressure as
that will commonly set misfire codes as well as the lean codes.
Thanks. I found a long video that went over at least some of the
things to do with a P0171. https://www.youtube.com/watch?v=SugtR4KMIDU

He ended up finding a leaky brake booster and a somewhat bad MAF sensor,
but more importantly he goes into some detail about what everything
means.

You and some of the other people here know everything that is in this
video. I miss the days when there were people here who knew less than I
do. They woudl benefit more from this post than you or the others here
will.
I don't know everything but I'm pretty good at diagnostic and repair
work on vehicles.

How much do you really want to know about modern engine diagnostics?

Oh where he is checking the hoses, a quick trick is to use carb cleaner
and spray it around the hoses. If the engine rpm suddenly jumps look in
the area you were spraying for a leak.


From what you posted you have a vacuum leak/pirate air issue as the
primary problem. You can use brake clean or carb cleaner, they are both
more or less paint thinners that burn ok. I use carb cleaner because the
older version of brake cleaner is chlorinated and generates toxic gas
when burned.

Oops, I don't want that. I ordered it online and haven't gotten it yet,
but it also says the original version is not flammable (unlike the other
three versions in green cans, without chlorine),

So how could it work at all if it's not flammable?

There's a chart about a fifth of the way down, comparing 5 different
version of Brakleen. Only in the red can is there chlorine but only that
one is Not Flammable!
https://www.amazon.com/CRC-05089-BRA..._t1_B000BXKZUQ

But in videos I watched, they're using Brakleen in that red can! Life
is so complicated.

The thing to remember though is that in the video he is working on a car
different than yours, some things apply, others don't. For instance MAF
flow, as engine sizes go up, MAF numbers increase even at idle to feed
the larger engine.

Yes, I see. The engine he's working on is only 4 cylinders. Mine is 6.
Try this
https://support.alldata.com/sites/ma...ing_110918.pdf

I'll print this and do as he says tomorrow.

Looking at the fuel trims that go up, then start coming down means that
it's a medium sized leak. As the throttle opens it goes past the point
where the pirate air is the main component and the mixture improves. If
it started improving immediately it would be a small leak.

Yes, I see.

For the sensor data you want to look at it live, and watch what it
actually reads, if the front sensors are changing voltages rapidly as
the engine runs and the rear sensors stay at a somewhat constant number
and don't vary like the fronts, the sensors are working and although
they may be worn, they are doing their job and the converters are working.
You may be surprised at where a vacuum leak can be, brake booster, PCV
system, intake manifold gaskets, a damaged port on the manifold, in the
EVAP system and a host of others, some external others internal.

I'll keep looking and look again at places I've looked.

OH the wuse of water for leaks is somewhat common, it's because you can
use it on a hot or cold engine or one where you have ignition sources
like open plug wires or bad coils. The amount of cleaner you will use
won't be an issue though, just be sure to start on a cold engine.
Usually something like an intake leak will get better as the engine
warms up so you want to catch it when it's cold.

Okay.

In alt.home.repair, on Thu, 8 Apr 2021 06:37:51 -0700 (PDT), trader_4
wrote:


Since he's fiddled around looking for a vacuum leak for awhile already and can't
find an obvious one, I'd suggest getting a schematic that shows all the vacuum lines.
Then it will be easier to figure out where they tap off from, how to separate that
section and plug it. Or try the smoke tester. I've never used one, but have read of
other people using them and sounds like in principle it would work.

Another guy didnt' buy or build a smoke machhine. He just smoked a
cigar, and it worked.

https://www.youtube.com/watch?v=LT5xFCn3cmk

He attached another hose to his brake booster hose, blew into it and
found smoke coming out at the EGR valve which had a cracked something or
other. Cost him a dollar.

I don't smoke. I wonder if there is a way to do this with only
exhaling?

micky wrote:
In rec.autos.tech, on Thu, 08 Apr 2021 02:05:14 -0400, "Steve W."
wrote:

Steve W. wrote:
Steve W. wrote:
micky wrote:
In rec.autos.tech, on Sat, 03 Apr 2021 02:07:24 -0400, "Steve W."
wrote:

Scott Dorsey wrote:
micky wrote:
In rec.autos.tech, on 27 Mar 2021 19:31:15 -0000,
(Scott Dorsey) wrote:

AK wrote:
I had an oxygen sensor replaced.

Prior to that I got 20 mpg in the city for my CX7.

Now I am getting 21.5 mpg.

Could that increase be due to the replacement of the O2 sensor?
If your O2 sensor was reading low and causing the computer to run the
engine too rich, then yes.
So if now I get codes P0171 and P0174, which means that both banks are
running lean, does that mean replacing the sensors will cause the
opposite of what AK had, richer mixturen and decreased mpg?
Changing the sensors will do nothing but show the same codes again.
Those codes you posted mean the sensors are working. They are seeing
that there is excess oxygen in the exhaust stream compared to what they
expect based on the incoming airflow numbers.
The issue is not them but in the engine. As both are full bank lean
codes I would look at the fuel trims and the O2 live data and check for
I did buy a code reader last year that would read the live data, but
what I should look for has been mostly a mystery since then, until the
video below. I found it a few days ago but just had time to watch it.

Cars are much more complicated than when I was a boy, or even a
teenager, and I've said for years and told quite a few people that
anyone smart enough to be a good mechanic these days could succeed in a
lot of fields.

vacuum leaks or an intake leak that is letting in unmetered air.
As you don't post any P0300 range codes I doubt it's fuel pressure as
that will commonly set misfire codes as well as the lean codes.
Thanks. I found a long video that went over at least some of the
things to do with a P0171. https://www.youtube.com/watch?v=SugtR4KMIDU

He ended up finding a leaky brake booster and a somewhat bad MAF sensor,
but more importantly he goes into some detail about what everything
means.

You and some of the other people here know everything that is in this
video. I miss the days when there were people here who knew less than I
do. They woudl benefit more from this post than you or the others here
will.
I don't know everything but I'm pretty good at diagnostic and repair
work on vehicles.

How much do you really want to know about modern engine diagnostics?

Oh where he is checking the hoses, a quick trick is to use carb cleaner
and spray it around the hoses. If the engine rpm suddenly jumps look in
the area you were spraying for a leak.

From what you posted you have a vacuum leak/pirate air issue as the
primary problem. You can use brake clean or carb cleaner, they are both
more or less paint thinners that burn ok. I use carb cleaner because the
older version of brake cleaner is chlorinated and generates toxic gas
when burned.

Oops, I don't want that. I ordered it online and haven't gotten it yet,
but it also says the original version is not flammable (unlike the other
three versions in green cans, without chlorine),

So how could it work at all if it's not flammable?

There's a chart about a fifth of the way down, comparing 5 different
version of Brakleen. Only in the red can is there chlorine but only that
one is Not Flammable!
https://www.amazon.com/CRC-05089-BRA..._t1_B000BXKZUQ

But in videos I watched, they're using Brakleen in that red can! Life
is so complicated.

The thing to remember though is that in the video he is working on a car
different than yours, some things apply, others don't. For instance MAF
flow, as engine sizes go up, MAF numbers increase even at idle to feed
the larger engine.

Yes, I see. The engine he's working on is only 4 cylinders. Mine is 6.
Try this
https://support.alldata.com/sites/ma...ing_110918.pdf

I'll print this and do as he says tomorrow.
Looking at the fuel trims that go up, then start coming down means that
it's a medium sized leak. As the throttle opens it goes past the point
where the pirate air is the main component and the mixture improves. If
it started improving immediately it would be a small leak.

Yes, I see.

For the sensor data you want to look at it live, and watch what it
actually reads, if the front sensors are changing voltages rapidly as
the engine runs and the rear sensors stay at a somewhat constant number
and don't vary like the fronts, the sensors are working and although
they may be worn, they are doing their job and the converters are working.
You may be surprised at where a vacuum leak can be, brake booster, PCV
system, intake manifold gaskets, a damaged port on the manifold, in the
EVAP system and a host of others, some external others internal.

I'll keep looking and look again at places I've looked.

OH the wuse of water for leaks is somewhat common, it's because you can
use it on a hot or cold engine or one where you have ignition sources
like open plug wires or bad coils. The amount of cleaner you will use
won't be an issue though, just be sure to start on a cold engine.
Usually something like an intake leak will get better as the engine
warms up so you want to catch it when it's cold.

Okay.

If you like visit 2carpros.com Put in as much info about your issue as
you can and one of the crew can look up the line routing and parts on
that car and give you much more info including pictures and other tests.

--
Steve W.

Here's another rather cheap way,
https://www.youtube.com/watch?v=LxvrIYq1jp0

He just uses a rubber balloon, a rubber glove, some tubing and a vape
pen.

--------------

In alt.home.repair, on Thu, 8 Apr 2021 06:37:51 -0700 (PDT), trader_4
wrote:


Since he's fiddled around looking for a vacuum leak for awhile already and can't
find an obvious one, I'd suggest getting a schematic that shows all the vacuum lines.
Then it will be easier to figure out where they tap off from, how to separate that
section and plug it. Or try the smoke tester. I've never used one, but have read of
other people using them and sounds like in principle it would work.

Another guy didnt' buy or build a smoke machhine. He just smoked a
cigar, and it worked.

https://www.youtube.com/watch?v=LT5xFCn3cmk

He attached another hose to his brake booster hose, blew into it and
found smoke coming out at the EGR valve which had a cracked something or
other. Cost him a dollar.

I don't smoke. I wonder if there is a way to do this with only
exhaling?

On Thursday, April 8, 2021 at 10:47:01 PM UTC-4, micky wrote:
In alt.home.repair, on Thu, 8 Apr 2021 06:37:51 -0700 (PDT), trader_4
wrote:

On Thursday, April 8, 2021 at 2:05:17 AM UTC-4, Steve W. wrote:
Steve W. wrote:
Steve W. wrote:
micky wrote:
In rec.autos.tech, on Sat, 03 Apr 2021 02:07:24 -0400, "Steve W."
wrote:

Scott Dorsey wrote:
micky wrote:
In rec.autos.tech, on 27 Mar 2021 19:31:15 -0000,
(Scott Dorsey) wrote:

AK wrote:
I had an oxygen sensor replaced.

Prior to that I got 20 mpg in the city for my CX7.

Now I am getting 21.5 mpg.

Could that increase be due to the replacement of the O2 sensor?
If your O2 sensor was reading low and causing the computer to run the
engine too rich, then yes.
So if now I get codes P0171 and P0174, which means that both banks are
running lean, does that mean replacing the sensors will cause the
opposite of what AK had, richer mixturen and decreased mpg?
Changing the sensors will do nothing but show the same codes again.
Those codes you posted mean the sensors are working. They are seeing
that there is excess oxygen in the exhaust stream compared to what they
expect based on the incoming airflow numbers.
The issue is not them but in the engine. As both are full bank lean
codes I would look at the fuel trims and the O2 live data and check for
I did buy a code reader last year that would read the live data, but
what I should look for has been mostly a mystery since then, until the
video below. I found it a few days ago but just had time to watch it.

Cars are much more complicated than when I was a boy, or even a
teenager, and I've said for years and told quite a few people that
anyone smart enough to be a good mechanic these days could succeed in a
lot of fields.

vacuum leaks or an intake leak that is letting in unmetered air.
As you don't post any P0300 range codes I doubt it's fuel pressure as
that will commonly set misfire codes as well as the lean codes.
Thanks. I found a long video that went over at least some of the
things to do with a P0171. https://www.youtube.com/watch?v=SugtR4KMIDU

He ended up finding a leaky brake booster and a somewhat bad MAF sensor,
but more importantly he goes into some detail about what everything
means.

You and some of the other people here know everything that is in this
video. I miss the days when there were people here who knew less than I
do. They woudl benefit more from this post than you or the others here
will.
I don't know everything but I'm pretty good at diagnostic and repair
work on vehicles.

How much do you really want to know about modern engine diagnostics?

Oh where he is checking the hoses, a quick trick is to use carb cleaner
and spray it around the hoses. If the engine rpm suddenly jumps look in
the area you were spraying for a leak.

From what you posted you have a vacuum leak/pirate air issue as the
primary problem. You can use brake clean or carb cleaner, they are both
more or less paint thinners that burn ok. I use carb cleaner because the
older version of brake cleaner is chlorinated and generates toxic gas
when burned.
The thing to remember though is that in the video he is working on a car
different than yours, some things apply, others don't. For instance MAF
flow, as engine sizes go up, MAF numbers increase even at idle to feed
the larger engine.
Try this
https://support.alldata.com/sites/ma...ing_110918.pdf

Looking at the fuel trims that go up, then start coming down means that
it's a medium sized leak. As the throttle opens it goes past the point
where the pirate air is the main component and the mixture improves. If
it started improving immediately it would be a small leak.

For the sensor data you want to look at it live, and watch what it
actually reads, if the front sensors are changing voltages rapidly the engine runs and the rear sensors stay at a somewhat constant number
and don't vary like the fronts, the sensors are working and although
they may be worn, they are doing their job and the converters are working.
You may be surprised at where a vacuum leak can be, brake booster, PCV
system, intake manifold gaskets, a damaged port on the manifold, in the
EVAP system and a host of others, some external others internal.
OH the wuse of water for leaks is somewhat common, it's because you can
use it on a hot or cold engine or one where you have ignition sources
like open plug wires or bad coils. The amount of cleaner you will use
won't be an issue though, just be sure to start on a cold engine.
Usually something like an intake leak will get better as the engine
warms up so you want to catch it when it's cold.


--
Steve W.

Since he's fiddled around looking for a vacuum leak for awhile already and can't
find an obvious one, I'd suggest getting a schematic that shows all the vacuum lines.
Under the hood is a partial schematic, of thoze hoses related to air
pollution. It doesn't include the brake booster, for example, becauae
I guess that has no effect on air pollution (except when the diaphragm
is broken and they don't count that! Because they only cover what the
law makes them cover.)

It also shows 4 vacuum switching valves, and so far I've only found 3 of
them. But this morning I disconnected the one connected to EVAP,
plugged the tube on the throttle body and it made no change at all in
the fuel trim. I also then disconnected the power brake booster,
plugged the tube, and it made no change in the fuel trim.


This one is very similar to the schematic for my car:
https://www.camryforums.com/forum/at...g-vachose3.jpg
You can click when the cursor ends in + and enlarge the photo.

Can anyone tell me what the rectangle with two hoses ocming out of it
is? It's above the MZ in 1MZ-FE at the bottom left of the picture. And
above the Vacuum Switching Valve that is above that. This part of my car
looks just like this. That is, there is a second VSV, what they label
the PWM Vacuum Switching Valve to the right of that white rectangle (and
if that were bad, they sell a replacement, from Toyota even.)

But the black-outlined white rectangle is just a silver box with two
hoses attached. And two screws holding it to the bracket above the fuel
rail. What does it do?

It's the release valve to burn the gas fumes from the gas tank, part of the
evaporative emissions control system.

On Thursday, April 8, 2021 at 11:13:25 PM UTC-4, micky wrote:
In rec.autos.tech, on Thu, 08 Apr 2021 02:05:14 -0400, "Steve W."
wrote:

Steve W. wrote:
Steve W. wrote:
micky wrote:
In rec.autos.tech, on Sat, 03 Apr 2021 02:07:24 -0400, "Steve W."
wrote:

Scott Dorsey wrote:
micky wrote:
In rec.autos.tech, on 27 Mar 2021 19:31:15 -0000,
(Scott Dorsey) wrote:

AK wrote:
I had an oxygen sensor replaced.

Prior to that I got 20 mpg in the city for my CX7.

Now I am getting 21.5 mpg.

Could that increase be due to the replacement of the O2 sensor?
If your O2 sensor was reading low and causing the computer to run the
engine too rich, then yes.
So if now I get codes P0171 and P0174, which means that both banks are
running lean, does that mean replacing the sensors will cause the
opposite of what AK had, richer mixturen and decreased mpg?
Changing the sensors will do nothing but show the same codes again.
Those codes you posted mean the sensors are working. They are seeing
that there is excess oxygen in the exhaust stream compared to what they
expect based on the incoming airflow numbers.
The issue is not them but in the engine. As both are full bank lean
codes I would look at the fuel trims and the O2 live data and check for
I did buy a code reader last year that would read the live data, but
what I should look for has been mostly a mystery since then, until the
video below. I found it a few days ago but just had time to watch it.

Cars are much more complicated than when I was a boy, or even a
teenager, and I've said for years and told quite a few people that
anyone smart enough to be a good mechanic these days could succeed in a
lot of fields.

vacuum leaks or an intake leak that is letting in unmetered air.
As you don't post any P0300 range codes I doubt it's fuel pressure as
that will commonly set misfire codes as well as the lean codes.
Thanks. I found a long video that went over at least some of the
things to do with a P0171. https://www.youtube.com/watch?v=SugtR4KMIDU

He ended up finding a leaky brake booster and a somewhat bad MAF sensor,
but more importantly he goes into some detail about what everything
means.

You and some of the other people here know everything that is in this
video. I miss the days when there were people here who knew less than I
do. They woudl benefit more from this post than you or the others here
will.
I don't know everything but I'm pretty good at diagnostic and repair
work on vehicles.

How much do you really want to know about modern engine diagnostics?

Oh where he is checking the hoses, a quick trick is to use carb cleaner
and spray it around the hoses. If the engine rpm suddenly jumps look in
the area you were spraying for a leak.


From what you posted you have a vacuum leak/pirate air issue as the
primary problem. You can use brake clean or carb cleaner, they are both
more or less paint thinners that burn ok. I use carb cleaner because the
older version of brake cleaner is chlorinated and generates toxic gas
when burned.
Oops, I don't want that. I ordered it online and haven't gotten it yet,
but it also says the original version is not flammable (unlike the other
three versions in green cans, without chlorine),

So how could it work at all if it's not flammable?

I was thinking about that when the poster said you could use brake cleaner.
But I wasn't sure if BC was flammable or not, especially now that there are
more environmentally friendly substances. You might still get some change
in how the engine runs, but good chance it's not noticeable, while injecting
a substance that's similar to gasoline will produce a noticeable change.

I'd have a hose and fire extinguisher handy. I've never had to resort to this,
but it doesn't sound too practical. It sounds fine if you see a few suspect
spots to try, but if you have to spray it around everywhere, along all the
hose runs, doesn't seem very practical. Plus you can't even get to many
spots and many of those are the most likely to fail, eg buried behind the
engine, running next to it where it gets hot and deteriorates, etc. One
advantage a dealer mechanic or similar has with this is they've seen many
of the same cars and know where the failure prone spots are so they know
exactly where to look or spray. I suppose you could get a garden sprayer,
fill it with gasoline and spray everywhere.....

On Friday, April 9, 2021 at 1:56:18 AM UTC-4, micky wrote:
In alt.home.repair, on Thu, 8 Apr 2021 06:37:51 -0700 (PDT), trader_4
wrote:


Since he's fiddled around looking for a vacuum leak for awhile already and can't
find an obvious one, I'd suggest getting a schematic that shows all the vacuum lines.
Then it will be easier to figure out where they tap off from, how to separate that
section and plug it. Or try the smoke tester. I've never used one, but have read of
other people using them and sounds like in principle it would work.
Another guy didnt' buy or build a smoke machhine. He just smoked a
cigar, and it worked.

https://www.youtube.com/watch?v=LT5xFCn3cmk

He attached another hose to his brake booster hose, blew into it and
found smoke coming out at the EGR valve which had a cracked something or
other. Cost him a dollar.

I don't smoke. I wonder if there is a way to do this with only
exhaling?

Cigars you don't inhale most of the smoke, only take it into your mouth to
get the flavor. It's worth a try. I'd get a Cohiba and try it out.

On Friday, April 9, 2021 at 8:03:54 AM UTC-4, trader_4 wrote:
On Thursday, April 8, 2021 at 10:47:01 PM UTC-4, micky wrote:
In alt.home.repair, on Thu, 8 Apr 2021 06:37:51 -0700 (PDT), trader_4
wrote:

On Thursday, April 8, 2021 at 2:05:17 AM UTC-4, Steve W. wrote:
Steve W. wrote:
Steve W. wrote:
micky wrote:
In rec.autos.tech, on Sat, 03 Apr 2021 02:07:24 -0400, "Steve W."
wrote:

Scott Dorsey wrote:
micky wrote:
In rec.autos.tech, on 27 Mar 2021 19:31:15 -0000,
(Scott Dorsey) wrote:

AK wrote:
I had an oxygen sensor replaced.

Prior to that I got 20 mpg in the city for my CX7.

Now I am getting 21.5 mpg.

Could that increase be due to the replacement of the O2 sensor?
If your O2 sensor was reading low and causing the computer to run the
engine too rich, then yes.
So if now I get codes P0171 and P0174, which means that both banks are
running lean, does that mean replacing the sensors will cause the
opposite of what AK had, richer mixturen and decreased mpg?
Changing the sensors will do nothing but show the same codes again.
Those codes you posted mean the sensors are working. They are seeing
that there is excess oxygen in the exhaust stream compared to what they
expect based on the incoming airflow numbers.
The issue is not them but in the engine. As both are full bank lean
codes I would look at the fuel trims and the O2 live data and check for
I did buy a code reader last year that would read the live data, but
what I should look for has been mostly a mystery since then, until the
video below. I found it a few days ago but just had time to watch it.

Cars are much more complicated than when I was a boy, or even a
teenager, and I've said for years and told quite a few people that
anyone smart enough to be a good mechanic these days could succeed in a
lot of fields.

vacuum leaks or an intake leak that is letting in unmetered air.
As you don't post any P0300 range codes I doubt it's fuel pressure as
that will commonly set misfire codes as well as the lean codes.
Thanks. I found a long video that went over at least some of the
things to do with a P0171. https://www.youtube.com/watch?v=SugtR4KMIDU

He ended up finding a leaky brake booster and a somewhat bad MAF sensor,
but more importantly he goes into some detail about what everything
means.

You and some of the other people here know everything that is in this
video. I miss the days when there were people here who knew less than I
do. They woudl benefit more from this post than you or the others here
will.
I don't know everything but I'm pretty good at diagnostic and repair
work on vehicles.

How much do you really want to know about modern engine diagnostics?

Oh where he is checking the hoses, a quick trick is to use carb cleaner
and spray it around the hoses. If the engine rpm suddenly jumps look in
the area you were spraying for a leak.

From what you posted you have a vacuum leak/pirate air issue as the
primary problem. You can use brake clean or carb cleaner, they are both
more or less paint thinners that burn ok. I use carb cleaner because the
older version of brake cleaner is chlorinated and generates toxic gas
when burned.
The thing to remember though is that in the video he is working on a car
different than yours, some things apply, others don't. For instance MAF
flow, as engine sizes go up, MAF numbers increase even at idle to feed
the larger engine.
Try this
https://support.alldata.com/sites/ma...ing_110918.pdf

Looking at the fuel trims that go up, then start coming down means that
it's a medium sized leak. As the throttle opens it goes past the point
where the pirate air is the main component and the mixture improves. If
it started improving immediately it would be a small leak.

For the sensor data you want to look at it live, and watch what it
actually reads, if the front sensors are changing voltages rapidly the engine runs and the rear sensors stay at a somewhat constant number
and don't vary like the fronts, the sensors are working and although
they may be worn, they are doing their job and the converters are working.
You may be surprised at where a vacuum leak can be, brake booster, PCV
system, intake manifold gaskets, a damaged port on the manifold, in the
EVAP system and a host of others, some external others internal.
OH the wuse of water for leaks is somewhat common, it's because you can
use it on a hot or cold engine or one where you have ignition sources
like open plug wires or bad coils. The amount of cleaner you will use
won't be an issue though, just be sure to start on a cold engine.
Usually something like an intake leak will get better as the engine
warms up so you want to catch it when it's cold.


--
Steve W.

Since he's fiddled around looking for a vacuum leak for awhile already and can't
find an obvious one, I'd suggest getting a schematic that shows all the vacuum lines.
Under the hood is a partial schematic, of thoze hoses related to air
pollution. It doesn't include the brake booster, for example, becauae
I guess that has no effect on air pollution (except when the diaphragm
is broken and they don't count that! Because they only cover what the
law makes them cover.)

It also shows 4 vacuum switching valves, and so far I've only found 3 of
them. But this morning I disconnected the one connected to EVAP,
plugged the tube on the throttle body and it made no change at all in
the fuel trim. I also then disconnected the power brake booster,
plugged the tube, and it made no change in the fuel trim.


This one is very similar to the schematic for my car:
https://www.camryforums.com/forum/at...g-vachose3.jpg
You can click when the cursor ends in + and enlarge the photo.

Can anyone tell me what the rectangle with two hoses ocming out of it
is? It's above the MZ in 1MZ-FE at the bottom left of the picture. And
above the Vacuum Switching Valve that is above that. This part of my car
looks just like this. That is, there is a second VSV, what they label
the PWM Vacuum Switching Valve to the right of that white rectangle (and
if that were bad, they sell a replacement, from Toyota even.)

But the black-outlined white rectangle is just a silver box with two
hoses attached. And two screws holding it to the bracket above the fuel
rail. What does it do?
It's the release valve to burn the gas fumes from the gas tank, part of the
evaporative emissions control system.

Also should have added that if there's a leak there it has to be between the
purge valve and the intake manifold. If there was a leak on the other side of
the valve you' should have fault codes for the evaporative emission system,
the computer monitors that for correct pressure.

In alt.home.repair, on Fri, 9 Apr 2021 05:18:28 -0700 (PDT), trader_4
wrote:

On Friday, April 9, 2021 at 1:56:18 AM UTC-4, micky wrote:
In alt.home.repair, on Thu, 8 Apr 2021 06:37:51 -0700 (PDT), trader_4
wrote:


Since he's fiddled around looking for a vacuum leak for awhile already and can't
find an obvious one, I'd suggest getting a schematic that shows all the vacuum lines.
Then it will be easier to figure out where they tap off from, how to separate that
section and plug it. Or try the smoke tester. I've never used one, but have read of
other people using them and sounds like in principle it would work.
Another guy didnt' buy or build a smoke machhine. He just smoked a
cigar, and it worked.

https://www.youtube.com/watch?v=LT5xFCn3cmk

He attached another hose to his brake booster hose, blew into it and
found smoke coming out at the EGR valve which had a cracked something or
other. Cost him a dollar.

I don't smoke. I wonder if there is a way to do this with only
exhaling?

Cigars you don't inhale most of the smoke, only take it into your mouth to
get the flavor.

Too risky for me. I'm not good at moderation and even putting it in my
mouth might get me hooked (not chemically but just 'cause I like it.)
That's why I trying to figure out if one could just light a cigar and
blow out through the cigar, and still collect the smoke in some tube
that goes to the intake manifold, etc.

But I gave up on that idea and ordered a vape kit. Should be here any
day. (I only found one kit that was complete with juice and dispenser
etc. $11 at elctrictobacconist. plus 12 or 13 shipping.
"Boulder"-something. I shouldn' promote it before iit comes. It may
be a disappointment.

All the others required buying separate vape juice and the cost would be
about $30 plus shipping. And the disposeables really are. When you
run out of liquid or electricity,theyi can't be refilled or recharged.
You dispose of them.

Flavored disposeables are not legal for sale in Marlyand and several
other states, cities, counties. Lots of rules.

It's worth a try. I'd get a Cohiba and try it out.

When I got to Mexico I used to tell people who offered me a cigarette,
"No fumar". Eventually I realized I'd read this on signs at gas
stations and it meant No Smoking. LOL

Just like the foreigners Americans laugh at when they mangle English.

So I changed to No fuMO. Sounded good but eventually I learned that
meant, I didn't smoke.

Just like the foreigners Americans laugh at when they mangle English.

Finally I knew enough Spanish to say No FUmo. It didnt' sound like
Spanish to me, but it is. I don't smoke.