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.....
