My '02 Tahoe L59 revs WAY too high on cold start ups. Anyone got any ideas?

[Marky Dissod]

Stipulating to posts 28 , 29 , and 30.

For the record:
a new IAC motor made no difference
the smoke-leak test that found no leaks was done with the engine warmed up, and the OE factory intake between the airbox and the throttle body removed

I'm PERFECTLY WILLING to fire the parts derringer (as in cheaper than the parts cannon) at an '02 vehicle, several times in fact.
What pieces / hoses of plastic / rubber would you replace on a 22 year old vehicle if you were a pragmatic pessimist?

Please understand: I'd be willing to pay for a diagnostic AGAIN, IF it would actually find and fix the problem.
But after spending $150 on a diagnostic session that came up with nothing, why NOT fire the parts derringer judiciously?

 

[iamdub]

Stipulating to posts 28 , 29 , and 30.

For the record:
a new IAC motor made no difference
the smoke-leak test that found no leaks was done with the engine warmed up, and the OE factory intake between the airbox and the throttle body removed

I'm PERFECTLY WILLING to fire the parts derringer (as in cheaper than the parts cannon) at an '02 vehicle, several times in fact.
What pieces / hoses of plastic / rubber would you replace on a 22 year old vehicle if you were a pragmatic pessimist?

Please understand: I'd be willing to pay for a diagnostic AGAIN, IF it would actually find and fix the problem.
But after spending $150 on a diagnostic session that came up with nothing, why NOT fire the parts derringer judiciously?

Do you have or have access to a scanner that will show live/real time data?

Did you clean the TB yet?

 

[Marky Dissod]

Do you have or have access to a scanner that will show live / real time data?
Did you clean the TB yet?

For at least a week, no access to live real time data.
As for cleaning the throttle body, and advice on what to use and how to use it?
Got several cans of brake cleaner, but want to be SURE it's safe to use on a throttle body / IAC motor / throttle position sensor.

 

[hagar]

The carbon restricts or completely stops the pintle from moving depending on where it gets wedged. It can wedge between the pintle and the inner bore of the IAC or behind or in front of the pintle reducing or completely stopping any movement inward and outward. This was a very common problem in the 2.8 V6 engine years ago. And high idle or rough idle was the symptom.

Absolutely. In this case it's possible it isn't able to go from its more open while cranking position, to less open right after it fires. It should never be open enough to flair to 2500 if the tune is stock though. On some gnarly vehicles I like to make them crack ******* cold starts and hop up to like 1500 for a couple seconds before settling down, but a stock truck wont have that parked position. Unless when it's warm the truck has an issue that causes the iac to be much more open than normal, then when he shuts it down and it cools, it sticks in the much more open position.
I still think it's an air leak causing the flair until the truck has a chance to close down the iac valve after start, but checking the iac valve is for sure a good idea.

 

[Fless]

For at least a week, no access to live real time data.
As for cleaning the throttle body, and advice on what to use and how to use it?
Got several cans of brake cleaner, but want to be SURE it's safe to use on a throttle body / IAC motor / throttle position sensor.

Pick up a can of throttle body cleaner and use that for the TB.

 

[iamdub]

For at least a week, no access to live real time data.
As for cleaning the throttle body, and advice on what to use and how to use it?
Got several cans of brake cleaner, but want to be SURE it's safe to use on a throttle body / IAC motor / throttle position sensor.

If you're removing the TB to clean it, you can use pretty much anything. There are no exposed "soft parts" other than the gasket. But, God invented a specific TB cleaner for a reason, so I'd have to recommend that. My hackjob ass would use one of the ~15 cans of brake cleaner I have in stock.

Spray on, let soak, scrub with a toothbrush, repeat. Finish with more spraying and blasts from an air compressor or towel and air dry.


These things aren't as fragile as one might think. When I did my delete, I wanted to clean the oil out of the intake manifold. Just as it came off the engine with the TB, injectors, MAP sensor, etc. still attached, I filled it with foaming engine degreaser, let it sit then used a baby bottle cleaning brush to scrub each of the runners. Then I hosed it out from all angles- through the TB, in each port and through the brake vacuum hose. Foamed and hosed it a few times until the water flushing out from all the ports was clear. Blew it out with high pressure and volume air until no water droplets came out of any holes. I was gentle with the movements of the throttle blade when I opened it. Was slow to push it open to get the sprayer into it and didn't let it slam shut.

 

[hagar]

Like others have said, you need to get a scanner on it. At warmed up temp you want to see the short and long term fuel trims, the IAC duty cycle, the engine and air intake Temps, and the rpms. There are others that can help further, but those are the important ones to get it almost for sure figured out if you post the info.

 

[hagar]

Like others have said, you need to get a scanner on it. At warmed up temp you want to see the short and long term fuel trims, the IAC duty cycle, the engine and air intake Temps, and the rpms. There are others that can help further, but those are the important ones to get it almost for sure figured out if you post the info.

Oh, and tps as well to make sure there isn't something wrong with it and it's showing more than 2 percent throttle at idle. If it is reporting more than 2 percent, it will kick it to the part throttle timing map which has higher timing and also throttle adders via the iac that will hang the idle.