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

[Marky Dissod]

Whenever I start my '02 Tahoe L59 cold (6 hrs cooldown or more), the engine briefly revs up over 1600RpM.
This morning, it wasn't even freezing outside, yet it revved itself to 2000RpM for a few seconds before settling down to 1000RpM.
The first five minutes, I REALLY gotta lean on the brake, or I'll flatten some oblivious idiotard in the crosswalk.
Physical throttle cable, by the way.

Although I doubt I would mind this problem if it were already April, another 3 months of winter cold starts scares me stupid.

How do I get the cold starts to not rev so damn high? Disconnect battery power for a few hours?

 

[Scottydoggs]

try cleaning the tb. air intake off open the butterfly and clean as much of the black crap out on the walls and the back side of the butterfly.

carb and choke cleaner and a old tooth brush and some rags does a good job to clean with.

 

[strutaeng]

Hook up a scanner with live data and try to see if the sensor reported values seem correct, or ballpark.

Does your truck have EGR? You may a vacuum leak that seals itself up after the engine warms up due to a gasket expanding and sealing from thermal expansion.

Probably wise to do a smoke test, but live data scanner will most likely give you enough information to determine what's the issue.

 

[iamdub]

I agree with the above replies and would add removing the IAC valve and cleaning the pintle and the seat in the side of the TB where it seals to. But, first, check the commanded versus actual throttle angle (should be expressed as %).

 

[Marky Dissod]

Appreciate your replies. Found a near-as-makes-no-difference identical throttle body assembly off an '02 GMT800.
Given that my IAC motor and Throttle Position Sensor are both at least 22 years old, should I fire the Genuine AC Delco parts derringer and get a new IAC motor & Throttle Position Sensor, and clean the ever-lovin schidt out of the throttle body?

Also, besides disconnecting the battery for a few hours, is there anything else I can do?
Is there such a thing as a 'throttle relearn' procedure, or anything else of that nature?

 

[iamdub]

Appreciate your replies. Found a near-as-makes-no-difference identical throttle body assembly off an '02 GMT800.
Given that my IAC motor and Throttle Position Sensor are both at least 22 years old, should I fire the Genuine AC Delco parts derringer and get a new IAC motor & Throttle Position Sensor, and clean the ever-lovin schidt out of the throttle body?

I'm always for proper diagnostics. But, if you're good with doing so, I wouldn't see it as being a total waste. Surely, being 22 years old and a lot more electromechanical than the newer ones, it would have some wear.

Also, besides disconnecting the battery for a few hours, is there anything else I can do?
Is there such a thing as a 'throttle relearn' procedure, or anything else of that nature?

You can reset the PCM to where it has to relearn idle. The proper way is to initiate it with a bi-directional scanner. I can't recommend it, but I've never had a problem doing it the backyard way of pulling the PCM fuses while it's running. You do that, turn the key off, replace the fuses then start it. It'll likely stall immediately. Just restart it. Don't give it throttle to keep it running. Let it figure it out on its own. If it starts and runs as it did before, then it didn't reset.

 

[strutaeng]

Is this drive by (edit) cable, right? Is there such thing as throttle relearn on that?

I've never wondered. Somehow I think that's just for drive by wire? IDK

 

[iamdub]

Is this drive by wire, right? Is there such thing as throttle relearn on that?

I've never wondered. Somehow I think that's just for drive by wire? IDK

'02 has a cable, IAC and separate TPS. The PCM uses the IAC to control the throttle.

On DBW, the PCM just opens the throttle blade to control idle.

 

[strutaeng]

'02 has a cable, IAC and separate TPS. The PCM uses the IAC to control the throttle.

On DBW, the PCM just opens the throttle blade to control idle.

Oops, meant drive by cable on my first sentence...will edit.

 

[Marky Dissod]

Physical real throttle.