Really rough start today

mannaggia · February 5, 2007

I started my 2002 Silverado today and it started right away but the engine raced as soon as it started and RPM's went up higher than normal (don't recall the number). Then the RPM's came down but the idle was really rough.

It's been idling a little rough upon starting for the past month or two since it got cold outside, but this was *really* rough. Then the Service Engine Soon light started flashing.

I turned it off, waited, then started it up again. The SES light stayed on for several seconds, then went off and the idle wasn't quite so bad. I let it sit for a few minutes, then drove off and it was OK for the rest of the day.

It's going to get really cold tonight, so I don't have a good feeling about starting it tomorrow. Any ideas about the possible cause?

wages999 · February 5, 2007

My '04 with 21,800 miles on it is acting the same way. It started idling rough, then ran okay for awhile. It got colder and it started idling rough again. The engine light started flashing and then it came on solid and the truck will barely idle. It's still under warranty, so as soon as I can get it to the dealer, I'll will find out what is wrong with it.

bobcat5544 · February 5, 2007

SEE BELOW FOR THE TSB ON THIS. THERE ARE OTHER POSSIBILITIES BUT THIS IS THE MOST COMMON

Document ID# 1619333

2002 Chevrolet Chevy K Silverado - 4WD

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Subject: 1999-2005 GEN III Cold Engine Misfire at Idle with Possible P0171 and/or P0174 - keywords 4.8 5.3 6.0 air cold crack hesitate idle intermittent internal intake L59 LR4 LM4 LM7 LQ4 LQ9 P0300 #PIP3232A - (03/08/2005)

Models:

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The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in the PI.

Condition/Concern:

99 through 05 GEN III truck engines may experience any of the following:

A cold rough idle that diminishes as the engine warms up.

Possible DTCs P0171, P0174, or P0300.

Random misfires at idle.

Recommendation/Instructions:

Check for leaking intake manifold seals around the intake ports. The intake gasket seals may be leaking around the intake ports, causing a lean condition. Many times they will leak around the bottom side of the port, making it a challenge to detect the vacuum leak. The technician may also note lower than normal MAF readings if the seals are leaking around the ports.

If leaking intake gasket seals are found, replace the gaskets with the updated part number of 89017589. The updated replacement gaskets part number 89017589 are teal green in color. The teal green gaskets will replace the original orange color intake gaskets.

The intake plenum should also be checked for excessive warpage that may cause an uneven clamping pressure of the seal. If the plenum is found to be warped it will need to be replaced. Service Information states, "An intake manifold with warpage in excess of 3 mm (0.118 in) over a 200 mm (7.87 in) area should be replaced". Intake warpage is measured at the gasket sealing surfaces and should be measured within a 200 mm (7.87 in) area. This measurement is across only two of the intake runner port openings. Measurements taken across the entire distance of all four intake runner ports will lead to unnecessary manifold replacements.

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.

Models:

(1999-2005 Chevrolet Silverado) and (1999-2005 Chevrolet Tahoe) and (1999-2005 Chevrolet Suburban) and (2002-2005 Chevrolet Avalanche) and (1999-2005 Chevrolet Express) and (2002-2005 Chevrolet Trailblazer) and (1999-2005 GMC Sierra) and (1999-2005 GMC Savana) and (1999-2005 GMC Yukon) and (1999-2005 GMC Yukon XL) and (1999-2005 GMC Denali) and (2002-2005 Cadillac Escalade) and (2003-2005 Hummer H2) and (2003-2005 GMC Envoy) and (2004-2005 Buick Rainer)

Bish · February 5, 2007

Symptom is same as when my IAC (Idle Air Control) valve gets dirty. First time it would barely idle and spiked or hunted for an idle speed. Pulled Throttle Body to clean and noticed the plunger for the IAC was filthy. I removed it and cleaned everything and the idle problem immediately went away. I now pull the TB every 40K or so to clean and the idle problem has not come back.

Good luck with your dealer.

mannaggia · February 6, 2007

SEE BELOW FOR THE TSB ON THIS. THERE ARE OTHER POSSIBILITIES BUT THIS IS THE MOST COMMON

Document ID# 1619333

2002 Chevrolet Chevy K Silverado - 4WD

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

Subject: 1999-2005 GEN III Cold Engine Misfire at Idle with Possible P0171 and/or P0174 - keywords 4.8 5.3 6.0 air cold crack hesitate idle intermittent internal intake L59 LR4 LM4 LM7 LQ4 LQ9 P0300 #PIP3232A - (03/08/2005)

Yep, took it to the dealer today and he quoted this TSB almost verbatim back to me... Thanks!

wages999 · February 7, 2007

My problem ended up being a bad O2 sensor that caused a bank to run lean and foul out the #5 spark plug.

brokedown · April 9, 2007

SEE BELOW FOR THE TSB ON THIS. THERE ARE OTHER POSSIBILITIES BUT THIS IS THE MOST COMMON

Document ID# 1619333

2002 Chevrolet Chevy K Silverado - 4WD

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

Subject: 1999-2005 GEN III Cold Engine Misfire at Idle with Possible P0171 and/or P0174 - keywords 4.8 5.3 6.0 air cold crack hesitate idle intermittent internal intake L59 LR4 LM4 LM7 LQ4 LQ9 P0300 #PIP3232A - (03/08/2005)

Models:

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

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in the PI.

Condition/Concern:

99 through 05 GEN III truck engines may experience any of the following:

A cold rough idle that diminishes as the engine warms up.

Possible DTCs P0171, P0174, or P0300.

Random misfires at idle.

Recommendation/Instructions:

Check for leaking intake manifold seals around the intake ports. The intake gasket seals may be leaking around the intake ports, causing a lean condition. Many times they will leak around the bottom side of the port, making it a challenge to detect the vacuum leak. The technician may also note lower than normal MAF readings if the seals are leaking around the ports.

If leaking intake gasket seals are found, replace the gaskets with the updated part number of 89017589. The updated replacement gaskets part number 89017589 are teal green in color. The teal green gaskets will replace the original orange color intake gaskets.

The intake plenum should also be checked for excessive warpage that may cause an uneven clamping pressure of the seal. If the plenum is found to be warped it will need to be replaced. Service Information states, "An intake manifold with warpage in excess of 3 mm (0.118 in) over a 200 mm (7.87 in) area should be replaced". Intake warpage is measured at the gasket sealing surfaces and should be measured within a 200 mm (7.87 in) area. This measurement is across only two of the intake runner port openings. Measurements taken across the entire distance of all four intake runner ports will lead to unnecessary manifold replacements.

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.

Models:

(1999-2005 Chevrolet Silverado) and (1999-2005 Chevrolet Tahoe) and (1999-2005 Chevrolet Suburban) and (2002-2005 Chevrolet Avalanche) and (1999-2005 Chevrolet Express) and (2002-2005 Chevrolet Trailblazer) and (1999-2005 GMC Sierra) and (1999-2005 GMC Savana) and (1999-2005 GMC Yukon) and (1999-2005 GMC Yukon XL) and (1999-2005 GMC Denali) and (2002-2005 Cadillac Escalade) and (2003-2005 Hummer H2) and (2003-2005 GMC Envoy) and (2004-2005 Buick Rainer)

I have a '01 z71 with 184,000 miles....getting random misfires on 1,3,5,7, to the point where it is not driveable. Have checked intake manifold, swapped coils/injectors to unaffected side, checked fuel pressure, replaced fpr, all with no results. What might be causing all cylinders on one side to misfire?