so i have an 02 chevy 2500HD 6.0 V8, and as soon as the outside tempurture drops below 60 degrees, my truck at cold start runs rough like its about to die, sometimes it does die, it does this for about 5 min till it warms its self up. i replaced the mass air flow thinking it was bad and it wasn't, when i unpluged the mass it runs a little better but i don't know what to do or whats up. atone poin i took it to a shop and they told me my intake manifold gasket was bad, my dad and i checked it out by blockin off the intake whail runing and spraying starting fluid around the gasket and it died from not getting air and my dad had to yank to get his hand off the intake. it has me lost and i don't want to spend tons of money to find my problem. if anyone could give me some advice that would be nice. thank you

 

MAF sensors are heated. With key on, amd MAF out of air inlet, can you feel it heating up? To accuratley measure flow you need temp. I think this is the cheap way that car makers do, heat the air at the sensor to a known value.

 

i have not felt it but i was wondering if the tempature sensor on the side of the block would be my problem. cause it runs great in the summer but as soon as its cold outside it wants to die.

 

Replace the intake gaskets common problem. Your description fits exactly. See it all the time GM has issued a TSB


Date: June 24, 2005

TECHNICAL

Subject:
Flexible Fuel (RPO L59) Rough Idle, Misfire, MIL DTC P0300
(Install Intake Manifold Gaskets With Teal Green Gasket Material)
Models:
2002-2004 Chevrolet Silverado, Suburban, Tahoe
2002-2004 GMC Sierra, Yukon, Yukon XL
with 5.3L Engine and Flexible Fuel (VIN Z - RPO L59)
This bulletin may apply to the following engines using regular fuel: 4.8L, 5.3L, 6.0L (VINs V, T, P, U, N - RPOs LR4, LM7, LM4, LQ4, LQ9).

Supercede:

This bulletin is being revised to add additional diagnostic information. Please discard Corporate Bulletin Number 05-06-04-029 (Section 06 - Engine/Propulsion System).

Important :Always begin your diagnosis with the Diagnostic System Check - Engine Controls (SI Document ID # 1289827) for any MIL or driveability concern. The Diagnostic System Check directs you to the next logical step in your diagnosis. Follow the instructions in this bulletin should the rough idle, misfire, or DTC P0300 diagnostic procedure point to an air leak in the intake manifold gasket. Following the published diagnostic procedures will improve diagnostic accuracy and support our fix it right the first time approach.
Condition

Some customers may comment that the vehicle may have a rough idle, misfires and/or a MIL illuminated with a stored DTC P0300.

Cause

The L59 engine is calibrated for ethanol fuel (E85). Due to the low volatility of ethanol, the PCM provides higher fuel flow through the injector, which may pool on the upper manifold to head gasket material. Overtime (usually 12 months and longer), the gasket material may degrade resulting in an unmetered air leak.

Correction

Replace the upper intake manifold gaskets with the teal green gasket material, P/N 89017589.

Important o not replace the upper intake manifold gaskets with the original orange gasket material, P/N 17113557.
Inspect Intake Manifold to Cylinder head Deck for Warpage

 

the intake manifold gasket? cause my dad and i found out its not bad. i thank you all for the info tho

 

Is the truck fixed?? The way you tested the intake gasket is not valid at all.

 

no its not fixed, i judt don't want to go through all that work to replace the intake manifold gasket just to find out its not it.

 

It is more than an 80% chance that it is the intake. I would actually need to see the truck to be 100% however you already have that diagnoses by a shop. It is very common. All testing would need to be done while the truck is at the temperature in which the problem happens. Most of the time the intake leak can not be found with without a smoke machine. The reason it happens is because the intake is plastic the gasket is plastic and rubber ( kind of o-ringed). At the cooler temps everything shrinks down causing not enough pressure on the o-ring gasket thus letting un metered air be sucked in. Further more they used a rubber material that is not completely compatible with fuel, thus the gasket update. When you unplug the MAF sensor the computer compensates for the lean condition. As the temperature increases everything expands thus sealing the leak and it runs fine. The leak is not huge (just enough to mess with fuel mixture) or the truck would not really run at all. By sealing the t- body with it running you are taking the MAF (fuel control) out and taking away all the air in, it can not run like that ever it just will not work. On carbureted car and TBI car you could check for a vac leak that way. The job is fairly easy (about 1 hour actual time in a shop) and the parts are not that expensive. It should be less money the throwing new OE electrical parts at it.

 

I would clean your idle air control valve and throttle body too since your right there anyways.

 

wow, thank you very much MDTahoe. you explained that in a very nice way that i could understand, i thank you very much. and thonyyang, i like the tip but i have alredy done that trying to see if there was a dirty sensor. thank you very much