Cold weather engine surge when warming up

KENNETH CRAIG

MEMBER
2002 GMC YUKON
V8
4WD
AUTOMATIC
125,000 MILES

I have a 5.3L GMC Yukon that surges terribly while warming up. The engine revs up to 2000 rpm then drops to below 900rpm, sometimes dying. It continually does this until it warms up, then it idles pretty smooth at about 800 to 900 rpm. Sometimes I have to keep the working the accelerator pedal to maintain about 2000 rpm till warm up. Can you advise me as to the solution to my problem? Thanks

1 Reply

SQM

MECHANIC
6,383 POSTS

Hello,

This could be due to a malfunctioning idle air control valve (IAC).
A faulty IAC can cause high idle or make it difficult for the engine to idle at all.

https://www.2carpros.com/articles/engine-idles-too-high

Another possibility is a vacuum leak. Which is allowing the throttle body to suck in excess air. And as the engine warms up the leak closes due to expansion on all the components and makes the idle go to a normal level.

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Sometimes cleaning out the IAC can improve the idle quality, as over time it will have dirt and debris buildup inside the valve.

https://www.2carpros.com/articles/idle-air-control-valve-service

I have attached diagrams for your reference.

Please let me know if you have any questions.
Thank you.

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