Need Help with a idling problem with engine....

1993 CHEVROLET LUMINA
150,000 MILES
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JEFFSELTER
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  • 2 POSTS
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.
Dec 2, 2011 at 5:30 AM
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WRENCHTECH
  • ✓Experienced Mechanic
  • 20,760 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.
Dec 2, 2011 at 6:50 AM
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JEFFSELTER
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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?
Dec 2, 2011 at 7:11 AM
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