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Need Help with a idling problem with engine.

Tiny
JEFFSELTER
  • MEMBER
  • 1993 CHEVROLET LUMINA
  • 150,000 MILES
I am working with a 1993 Chevrolet Lumina z-34 Problem is that I cannot get the idle of the engine to remain correct. I have replaced the IAC installed to the correct specs of 1 1/8 " of the rod stroke. Starts the engine and it will perform perfectly, set the idle correctly, and drive it around the block a few times. Shut it off and re - start the engine and it runs great, however park the car go back out later start the car to drive it and the engine races at a very fast rpm. And will not change back to the correct idle. Also replaced the TPS as a precaution. I am wondering if the ECM is malfunctioning or not controlling these components correctly.
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Friday, December 2nd, 2011 AT 1:30 PM

2 Replies

Tiny
WRENCHTECH
  • MECHANIC
  • 20,761 POSTS
I'm not sure what specs you are referring to with the IAC but they just install "as is" You could have a worn out throttle body causing issues. Make sure you have scrubbed it clean and lubricated the shaft.
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Friday, December 2nd, 2011 AT 2:50 PM
Tiny
JEFFSELTER
  • MEMBER
  • 2 POSTS
Thank you for your answer. The specs that I am talking about came with the IAC partit says that it must be 1 1/8 prior to installation. There is nothing worn in the throttle body, cleaned it and all is working properly there. My question is how can it run perfectly one minute and I shut it off and turn it back on a short time later and the engine is still racing. Idling at about 2000 RPM. Could it be the ECM?
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Friday, December 2nd, 2011 AT 3:11 PM

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