Cold Idle Issues

yfz450_117 · January 27, 2007

Hey guys,

This is my first post on here. Great site! I have a 2002 Silverado 1500HD. I'm having some cold idle issues. It starts fine. Idles up to around 1200rpms, then it dips way down to around 500 (normal idle) and spits and sputteres then it will surge back up to around 1000rpms. It does this for the first 2 minutes or so of running. It is like it is too cold for it to idle that low. Once the truck has been running for a good 3-4 minutes, it gets better and better until it is warmed up then it is completely fine for the rest of the day. It only happens when I let it sit overnight for like 10 hours. The colder the weather the worse it is. It actually shuts off on me. This morning it shut off twice on me. I've replaced the coolant temp sensor and that didn't help. I've cleaned the throttle body and IAC valve and that seemed to help it run a little better. It seemed like it had a bit more power, but it didn't help with my cold idle issue. My mechanic is pretty confident that it is still the IAC valve. Even though I cleaned it, it still may not be working properly. I was going to check for an intake leak today using the starting fluid method and see what I come up with. My mechanic is steering me away from the intake leak. He says it would do it all the time if it was the intake, not just when cold. I guess my question is, is it sometime necessary to replace the IAC valve?? Does cleaning it not always cure the problem?? The IAC valve is $120 bucks at advanced auto that is why im hesitant on getting it. Could it be the throttle position sensor? I can get that sensor for $30 bucks. Thanks in advance for your help.

chevroletmb · January 27, 2007

actually it sounds like intake gaskets to me. i've seen a few truck run like crap until they warmed up there's even a tsb on it.

StoneyPgh · January 27, 2007

Hey guys,
This is my first post on here. Great site! I have a 2002 Silverado 1500HD. I'm having some cold idle issues. It starts fine. Idles up to around 1200rpms, then it dips way down to around 500 (normal idle) and spits and sputteres then it will surge back up to around 1000rpms. It does this for the first 2 minutes or so of running. It is like it is too cold for it to idle that low. Once the truck has been running for a good 3-4 minutes, it gets better and better until it is warmed up then it is completely fine for the rest of the day. It only happens when I let it sit overnight for like 10 hours. The colder the weather the worse it is. It actually shuts off on me. This morning it shut off twice on me. I've replaced the coolant temp sensor and that didn't help. I've cleaned the throttle body and IAC valve and that seemed to help it run a little better. It seemed like it had a bit more power, but it didn't help with my cold idle issue. My mechanic is pretty confident that it is still the IAC valve. Even though I cleaned it, it still may not be working properly. I was going to check for an intake leak today using the starting fluid method and see what I come up with. My mechanic is steering me away from the intake leak. He says it would do it all the time if it was the intake, not just when cold. I guess my question is, is it sometime necessary to replace the IAC valve?? Does cleaning it not always cure the problem?? The IAC valve is $120 bucks at advanced auto that is why im hesitant on getting it. Could it be the throttle position sensor? I can get that sensor for $30 bucks. Thanks in advance for your help.

I hope someone has the answer, 'cause I have also just started having this problem.

Also, a question about the "improvements to the format. I don't see any way to track a thread without posting in it. Tried the "options" drop-down menu, but it does not display.

Have I missed something, or is the problem temporary?

yfz450_117 · January 27, 2007

actually it sounds like intake gaskets to me. i've seen a few truck run like crap until they warmed up there's even a tsb on it.

Would checking them with the starting fluid method get me anywhere? Spraying it around the base of the intake while it's running and listening for a change in idle.

This is probably a stupid question but what is a tsb??

Thanks.

StoneyPgh · January 27, 2007

This is probably a stupid question but what is a tsb??

Thanks.

tsb is Tech Service Bulletin

yfz450_117 · January 27, 2007

This is probably a stupid question but what is a tsb??

Thanks.

tsb is Tech Service Bulletin

I tought it was something along those lines. Thanks for clearing it up for me.

I just got done checking for an intake leak. I used carb cleaner and sprayed around the base of the intake. It one spot (passenger side front) I could get a slight, and I mean very slight stumble when I sprayed the carb cleaner there. I'm guessing that means I have an intake leak??

Thanks

cbxeric · January 28, 2007

There are several threads around that talk about this very problem. So far no thread that I've found gives a smoking gun answer. Owners have changed out practically every sensor (including me) only to have no improvement. I am leaning towards either a bad ground or an intake leak.

KB06YUKONXL · January 28, 2007

This is probably a stupid question but what is a tsb??

Thanks.

tsb is Tech Service Bulletin

I tought it was something along those lines. Thanks for clearing it up for me.

I just got done checking for an intake leak. I used carb cleaner and sprayed around the base of the intake. It one spot (passenger side front) I could get a slight, and I mean very slight stumble when I sprayed the carb cleaner there. I'm guessing that means I have an intake leak??

Thanks

Sound like an intake leak to me. I had the same issue on one of my Harleys's once and that's exactly how I diagnosed it. You may want to find the torque values for the intake fasteners and retorque before you remove it to replace the gasket. You could have a loose fastener.

GeoHawk · January 28, 2007

Could be this....

Document ID# 1619333

2003 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)

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.

WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION

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Document ID# 1619333

2003 Chevrolet Chevy K Silverado - 4WD