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Help with High Idle on 85

James Guard

Aug 25, 2019
wilmington, Ohio
Can't figure out the high idle issue I'm having with my 85. It wants to idle around 1400. I tried setting the idle with the IAC procedure per the FSM which seems to fix the problem after I shut the car off and restart it, it reverts back to the high idle. I have also adjusted the TPS with no change. Could this be a bad ECM? What else can I check? Also, is there a module that controls the check engine light? I have replaced the bulbs, replaced the info panel, and I still do not have a check engine light to check for codes using the paper clip method. Any suggestions? I'm looking for serious help with these issues. I have put a lot of hours restoring this car to have it not run is not acceptable. I am a Corvette noob so I need the guidance from the experts. Thanks guys.
Last edited:
High idle is often caused by a vacuum leak. Have you inspected the induction system beyond the throttle body for vacuum leaks?

Do you have the '85 Service Manual.
If not, buy one.

There is diagnostic information on what to do when the check engine light is not working.

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