I currently have no code. However I took data on my scanner twice. The
truck sputtered and ran a little rough as soon as I left the driveway.
It seem though the further I went it started to get better. Truck has
had a catylist system efficiency below threshold for a number of
months. I assumed it was a catalytic converter and would not be
related. Truck has 342,000 miles. New plugs, wires, cap and rotor in
April. Today I replaced Ignition control module and ignition coil.
Ensured continuity with battery ground on the ICM harness. Ensured
continuity on the white wire from computer to ICM.



Problem started as what felt like "slipping" several weeks ago when
leaving for work. Did not seem to be getting as many miles pertank
either.) Never had that problem again for the rest of the day. This
lasted for a few weeks. I put two bottles of fuel injection cleaner in
tank and filled up tank. A few days later went out to start and took
forever to start. Once did ran rough. Got the code P1351. Did above
diagostics. Getting 6 colts to the ICM harness. (calls for 1-4 in
book). Checked crank sensor. It is supposed to output "approximately"
5 volts but is outputting 4. Cleaned with a wire brush chasis ground.
Code has not come back yet but I have not driven truck other than to
do the data test a few minutes ago. (And still seem to be exhibiting
problems).



On a whim I checked fuel pressure. It was within specs at 64 psi.
(Calls for 60-65). However, when turning the key off the pressure
drops down a great deal. In 5 minutes it dropped 30 psi. I think my
Haynes manual says this is abnormal but not sure.



is the truck safe to drive to work? It seems to get better as it warms
up but I dont want to get stranded. It is my daily driver and I dont
know what to do.



Here is the data I downloaded:





Location #1 (Test
1)



DTC-cnt 0



Fuel Sys 1 OL



Fuel Sys 2 OL



Load_PCT(%) 4.7



ETC (F) 108



Shrt Ft1 (%) -3.1



LongFt1(%) 0.0



Shrt FT2 (%) -3.9



LongFT2 (%) 0.0



MAP (in HG) 11.5



RPM (/min) 668



VSS (MPH) 0



Spark ADVC -19



IAT (F) 70



MAF (1b/min) 1.198



TP (%) 0.0



02sB1S12—B2S12—



O2B1S2 (v) 0.230



SHRTFTB1S1 (%) -3.9



O2B1S2 (v) 0.340



O2B2S1 (V) 0.130



SHRT FT B2S1 (%) -5.5



O2B2S2 (v) 0.070



OBD OBD2



Location #2 (Test
2)



DTC-cnt 0



Fuel Sys 1 CL



Fuel Sys 2 CL



Load_PCT(%) 17.6



ETC (F) 205



Shrt Ft1 (%) 1.6



LongFt1(%) 0.0



Shrt FT2 (%) 1.6



LongFT2 (%) 0.0



MAP (in HG) 26.6



RPM (/min) 1505



VSS (MPH) 41



Spark ADVC -15



IAT (F) 70



MAF (1b/min) 8.279



TP (%) 42.4



02sB1S12—B2S12—



O2B1S2 (v) 0.100



SHRTFTB1S1 (%) 3.9



O2B1S2 (v) 0.670



O2B2S1 (V) 0.110



SHRT FT B2S1 (%) 3.1



O2B2S2 (v) 0.800



OBD OBD2

On 11/26/2011 3:48 PM, stryped wrote:
I currently have no code. However I took data on my scanner twice. The
truck sputtered and ran a little rough as soon as I left the driveway.
It seem though the further I went it started to get better. Truck has
had a catylist system efficiency below threshold for a number of
months. I assumed it was a catalytic converter and would not be
related. Truck has 342,000 miles. New plugs, wires, cap and rotor in
April. Today I replaced Ignition control module and ignition coil.
Ensured continuity with battery ground on the ICM harness. Ensured
continuity on the white wire from computer to ICM.



Problem started as what felt like "slipping" several weeks ago when
leaving for work. Did not seem to be getting as many miles pertank
either.) Never had that problem again for the rest of the day. This
lasted for a few weeks. I put two bottles of fuel injection cleaner in
tank and filled up tank. A few days later went out to start and took
forever to start. Once did ran rough. Got the code P1351....

Don't have handy access to codes here--what is P1351 specifically?

Wouldn't rule out the O2 sensor or related w/ the catalytic converter;
it's all thrown into the mix in the PCM.

Doesn't sound like the issue w/ the PCM of intermittent surging at all
from this description. That's a hit'n'miss thing that is very
noticeable when it's doing it but quits entirely when the module behaves
properly. It's on-off, not gradual or better-worse.

--

Have you ever replaced the catalytic converter? It is my understanding
that they eventually plug up and the vehicle runs poorly until you
change it. Be advised that this comment is based on your mentioning 342K
miles and catalytic efficiency, not my spreading the runes on the data
you provided.

My experience with taking difficult drivablilty problems to the dealer
is that they shotgun it to the tune of about $800 a trip until they find
it or you get tired of shelling out the money.

Good Luck,
BobH

On 11/26/2011 2:48 PM, stryped wrote:
I currently have no code. However I took data on my scanner twice. The
truck sputtered and ran a little rough as soon as I left the driveway.
It seem though the further I went it started to get better. Truck has
had a catylist system efficiency below threshold for a number of
months. I assumed it was a catalytic converter and would not be
related. Truck has 342,000 miles. New plugs, wires, cap and rotor in
April. Today I replaced Ignition control module and ignition coil.
Ensured continuity with battery ground on the ICM harness. Ensured
continuity on the white wire from computer to ICM.



Problem started as what felt like "slipping" several weeks ago when
leaving for work. Did not seem to be getting as many miles pertank
either.) Never had that problem again for the rest of the day. This
lasted for a few weeks. I put two bottles of fuel injection cleaner in
tank and filled up tank. A few days later went out to start and took
forever to start. Once did ran rough. Got the code P1351. Did above
diagostics. Getting 6 colts to the ICM harness. (calls for 1-4 in
book). Checked crank sensor. It is supposed to output "approximately"
5 volts but is outputting 4. Cleaned with a wire brush chasis ground.
Code has not come back yet but I have not driven truck other than to
do the data test a few minutes ago. (And still seem to be exhibiting
problems).



On a whim I checked fuel pressure. It was within specs at 64 psi.
(Calls for 60-65). However, when turning the key off the pressure
drops down a great deal. In 5 minutes it dropped 30 psi. I think my
Haynes manual says this is abnormal but not sure.



is the truck safe to drive to work? It seems to get better as it warms
up but I dont want to get stranded. It is my daily driver and I dont
know what to do.



Here is the data I downloaded:





Location #1 (Test
1)



DTC-cnt 0



Fuel Sys 1 OL



Fuel Sys 2 OL



Load_PCT(%) 4.7



ETC (F) 108



Shrt Ft1 (%) -3.1



LongFt1(%) 0.0



Shrt FT2 (%) -3.9



LongFT2 (%) 0.0



MAP (in HG) 11.5



RPM (/min) 668



VSS (MPH) 0



Spark ADVC -19



IAT (F) 70



MAF (1b/min) 1.198



TP (%) 0.0



02sB1S12—B2S12—



O2B1S2 (v) 0.230



SHRTFTB1S1 (%) -3.9



O2B1S2 (v) 0.340



O2B2S1 (V) 0.130



SHRT FT B2S1 (%) -5.5



O2B2S2 (v) 0.070



OBD OBD2



Location #2 (Test
2)



DTC-cnt 0



Fuel Sys 1 CL



Fuel Sys 2 CL



Load_PCT(%) 17.6



ETC (F) 205



Shrt Ft1 (%) 1.6



LongFt1(%) 0.0



Shrt FT2 (%) 1.6



LongFT2 (%) 0.0



MAP (in HG) 26.6



RPM (/min) 1505



VSS (MPH) 41



Spark ADVC -15



IAT (F) 70



MAF (1b/min) 8.279



TP (%) 42.4



02sB1S12—B2S12—



O2B1S2 (v) 0.100



SHRTFTB1S1 (%) 3.9



O2B1S2 (v) 0.670



O2B2S1 (V) 0.110



SHRT FT B2S1 (%) 3.1



O2B2S2 (v) 0.800



OBD OBD2

Fix your fuel pressure problem first. Not every issue is electronic or
detectable by OBD II.

On Sat, 26 Nov 2011 15:25:28 -0800 (PST), Frunobulax
wrote:

Fix your fuel pressure problem first. Not every issue is electronic or
detectable by OBD II.

Agreed - See what the book says on the fuel pressures, and check it
while running. There's a pressure regulator that bleeds off the
excess and bypasses to the tank, and some are fancy and vary the
pressure with RPM and load.

Do the basics, sparkplugs, air filter, clean out the throttle body...

At that mileage it might be due for plug wires and other secondary
ignition stuff, too.

-- Bruce --

On 11/26/2011 5:25 PM, Frunobulax wrote:
Fix your fuel pressure problem first. Not every issue is electronic or
detectable by OBD II.

And if the pressure drops rapidly after the pump stops, it is one of two
things--the check valve in the tank mounted pump, or, more likely the
regulator.

Find the rubber section of fuel hoses, and pinch off the return line
(skinnier) with vise grips over a rag and if the pressure still drops
rapidly (say, less than 5 minutes), the problem is the check valve in
the fuel pump (replace the pump). If pinching off the return line stops
the pressure loss, the problem is a leaky regulator.

And, btw, the regulator can be changed out w/o replacing the full "spider"

Haynes _ought_ to have this in it I'd think.

--

On Nov 27, 1:17*pm, dpb wrote:
On 11/26/2011 5:25 PM, Frunobulax wrote:

Fix your fuel pressure problem first. Not every issue is electronic or
detectable by OBD II.

And if the pressure drops rapidly after the pump stops, it is one of two
things--the check valve in the tank mounted pump, or, more likely the
regulator.

Find the rubber section of fuel hoses, and pinch off the return line
(skinnier) with vise grips over a rag and if the pressure still drops
rapidly (say, less than 5 minutes), the problem is the check valve in
the fuel pump (replace the pump). *If pinching off the return line stops
the pressure loss, the problem is a leaky regulator.

And, btw, the regulator can be changed out w/o replacing the full "spider"

Haynes _ought_ to have this in it I'd think.

--

So do I leave it unpressurized, pinch the return line, then turn KOEO
then turn off the key and see if the pressure holds? Is it ok to pinch
the rubber hose? (My manual says not to. Says somethig about putting
in a fuel cut off but I dont have one and not sure where I would get
one.

Does the upper intake have to be taken off to acess the "spider" and
change the regulator? I have never messed with one of these before.
Always had a Ford until now.

I will say my dad owned this truck before I got it from him. He had
the dealer put a new pump on it about 100,000 miles ago.

I do appreciate it. And becasue I knew the cat was bad, last night I
drilled it out. It started this morning and seemed to run ok down the
road about 10 miles. But I would feel better getting this fuel
pressure issue solved before I start driving the truck again.

"dpb" wrote in message ...
On 11/26/2011 5:25 PM, Frunobulax wrote:
Fix your fuel pressure problem first. Not every issue is electronic or
detectable by OBD II.

And if the pressure drops rapidly after the pump stops, it is one of two
things--the check valve in the tank mounted pump, or, more likely the
regulator.

More likely... the injector is leaking or sticking.
There is a complete updated fuel injector kit for these engines, a
Google search for "gm spider injector" will show dozens of people have the
same or similar problems. The $300 kit is he
http://www.gmpartsdirect.com/results.cfm