Engine Misfires

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PEKSAV:
Hello,
I have a 2002 AV 5.7 4x4 up here in Minnesota.  Whenever the temp hits below 32 degrees, the AV runs very rough at a cold start.  I sounds like it misfires, badly.  I put a OBD II scanner on it and the code showed multiple misfires, no kidding.  I know it misfires, I need to know why?  The manual shows three pages of possible code it can scan for, and all I can get is multiple  misfire.  When it warms up, it's runs OK.  Would it be worth taking it to a dealer and putting it on a scope?  Any ideas??

thanks

sperry:
I presume that was a P0300.

OK, cats plugged can do it.. Then the rich fuel makes that worse.

`Doubt that's a fuel filter since you didn't state any particuler fuel starvation problem.

If some sensors were at fault MAP MAF... Likely a code would show for them.

I'll see if I may have posted something regarding isolating it.

sperry:
Hmmm, here's a few...

 Document ID# 1537547
2002 Chevrolet Avalanche - 4WD
   
 
97-05 Vehicles with 4.8 5.3 5.7 and 6.0 Gen III V8 Engines and Misfires on One Bank - kw CEL diagnostics driveability DTC P0171 P0172 P0174 P0175 P0300 P0301 P0302 P0303 P0304 P0305 P0306 P0307 P0308 #PIP3056 - (Jul 12, 2004)

The following diagnosis might be helpful if the vehicle exhibits the described symptoms in the PI.

Condition/Concern:

Check Engine Light with a P0300 due to 2 - 4 cylinders misfiring on the same bank of the engine. DTCs P0171, P0172, P0174 or P0175 may also set for the misfiring bank.

Recommendation/Instructions:

If the published misfire diagnostic does not isolate the cause, perform the following suggestions as necessary:

   1. Perform a fuel injector balance test for all 8 cylinders. If a fuel injector concern exists, it is possible to misfuel an entire bank of the engine, causing multiple cylinders on the same bank to misfire even though the root cause is a single fuel injector.
   2. Inspect O2 sensor connections on the misfiring bank for corrosion or water intrusion. If water intrusion is found on the right bank, it may be due to the AC Evaporator Condensation dripping onto the O2 sensor harness. If this condition is found, reposition and shield the harness to prevent a repeat concern and repair the connections.
   3. Check for excessive exhaust backpressure using the restricted exhaust diagnosis from SI.
   4. Swap the Position 1 O2 sensors side to side to see if the misfires move to the other bank of the engine. If so, replace the O2 sensor.

Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance.

Models:

(00 - 05 Cadillac Escalade - C6 and K6) and (02 - 05 Chevrolet Avalanche - C1, C2 K1 and K2) and (99 - 05 Chevrolet Silverado - C1, C2 K1 and K2) and (00 - 05 Chevrolet Suburban - C1, C2, K1 and K2) and (00 - 05 Chevrolet Tahoe - C1 and K1) and (99 - 05 GMC Sierra C1, C2 K1 and K2) and (00 - 05 GMC Yukon - C1, C2, K1 and K2) and (03 - 05 Chevrolet Express G1, G2, G3, H1, H2 ) and (03 - 05 GMC Savana G1, G2, G3, H1, H2 ) and (04 - 05 Buick Rainier S1, T1 ) and (03 - 05 Chevrolet Trail Blazer EXT S1, T1 ) and (03 - 05 GMC Envoy XL XUV S1, T1 ) and (03 - 05 Hummer H2) and (04 - 05 Cadillac CTS-V DB) and (98 - 02 Chevrolet Camaro FB) and (97 - 04 Chevrolet Corvette YB) and (98 - 02 Pontiac Firebird FB) and (04 - 05 Pontiac GTO VB)

sperry:
 Document ID# 1537466
2002 Chevrolet Avalanche - 4WD

99-05 Full Size Trucks, Utilities and Vans with 4.8 5.3 6.0 V8 Engines That Have a P0300 Due to Fuel Contamination Cylinder 7 Misfire - kw CEL code contaminated DTC fuel gas L59 LM7 LR4 LQ4 LQ9 miss #PIP3055 - (Jul 8, 2004)

The following diagnosis might be helpful if the vehicle exhibits the described symptoms in the PI.

Condition/Concern:

Service Engine Soon Light with a P0300 misfire due to misfires mainly on cylinder 7. A possible cause could be fuel contamination. If present, the contaminated fuel will collect around the #7 fuel injector due to the fuel rail configuration in these vehicles. This issue can also cause some random misfires on cylinder 2 and 8 since they are next to cylinder 7 in the firing order.

Recommendation/Instructions:

If the published misfire diagnostics does not isolate the concern, the following suggestions may help if the misfire is related to fuel contamination:

   1. When the lines are removed, cap the fuel rail off to retain any fuel that might be contaminated. Remove the rail, drain it into a clear container and inspect for contamination.
   2. If contamination is found, follow the Fuel System Cleaning procedure in Service Information.
   3. Once the fuel system is cleaned, refill the fuel system with new gasoline.
   4. Advise the customer that they should only use gasoline from a high quality, high volume filling station.

If this is a 99 - 00 Chevrolet Silverado or GMC Sierra, also review 00-06-04-024. This bulletin relates to an updated EVAP vent valve to prevent water from being drawn in through the EVAP Vent Valve, which may lead to repeat fuel contamination.

Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance.

Models:

(01 - 05 Cadillac Escalade C1, C6, K1, K6) and (02 - 05 Chevrolet Avalanche C1, K1, C2, K2) and ((03 - 05 Chevrolet Express G1, G2, G3, H1, H2) and (99 - 05 Chevrolet Silverado Truck C1, K1, C2, K2, C3, K3 ) and (00 - 05 Chevrolet Tahoe C1, K1 ) and (00 - 05 Chevrolet Suburban C1, K1, C2, K2, C3, K3 ) and (03 - 05 GMC Savana G1, G2, G3, H1, H2 ) and (99 - 05 GMC Sierra Truck C1, K1, C2, K2, C3, K3 ) and (00 - 05 GMC Yukon C1, K1 ) and (00 - 05 GMC Yukon XL C1, K2, C2, K2, C3, K3) and (03 - 05 Hummer H2 N2 )

sperry:
 Document ID# 1424672
2002 Chevrolet Avalanche - 4WD

Info - Misfire DTCs P0300, P1380, P1381 and Catalytic Converter Damage Due to Installation of Alarm Systems #02-06-05-004A - (Jan 9, 2004)

2004 and Prior GM Passenger Cars and Light Duty Trucks

2003-2004 HUMMER H2

2004 and Prior Isuzu Light Duty Trucks

This bulletin is being revised to add the 2004 model year and include specific DTCs in the title line. Please discard Corporate Bulletin Number 02-06-05-004 (Section 06 - Engine/Propulsion System).

General Motors Engineering, in an effort to determine the root cause of catalytic converter damage, has determined that aftermarket alarm systems incorrectly installed in vehicles have the potential to cause misfire codes and damage to the converter. These alarm systems use a circuit interrupt which utilizes the ignition circuit on the vehicles.

These alarm systems utilize mechanical relays and normal vehicle movement can trigger these relays to engage and disengage the ignition circuit while the vehicle is in motion. These disruptions of the ignition circuit, which occur in milliseconds, may cause more fuel to be commanded. Over time, this dumping of fuel on and off again can cause misfire codes and ultimately damage the converter assembly.

Important

Engineering could not identify any alarms that utilize solid state circuitry that would eliminate this concern. Because of this, it has been determined that all alarm systems must be routed through the starter circuit in order to avoid this condition.

Dealers must be aware of this issue and take note of the wiring on vehicles with alarm systems that come in for repair, particularly for catalytic converter damage that seem to have no known root cause.

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