Question about 1990 Chevrolet Corvette

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Corvette 1990 5.7L Slow Idle Automatic

I have 1990 Corvette 5.7L Automatic, 22000 mile, that runs fine when I get on the gas but surges on slow idle and almost seems like it's going to stall. Come to a light or stop sign, I have to put it in neutral or park so the idle will be a little faster to solve the slow idle problem. This only happens when it is warmed up and the slow idle drops to 500 rpms. I replaced the following parts and the problem still exists:
ECM
Coolant temperature sensor
Throttle postition switch
Fuel filter
MAP sensor
Cleaned the throttle body

No codes are present in the ECM. I would appreciate any help you can give me with this problem

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  • dperreault Aug 05, 2008

    The only code that came up was code 35 the EGR valve and I replaced it.

  • yadayada
    yadayada May 11, 2010

    You said you cleaned the throttle body, did you spray cleaner into to the IAC, (idle air control valve), you must do this with the engine running so the cleaner is pulled through the valve, hold the idle high while you do this, when the spray can is about 1/2 empty let it stall, turn off key, disconnect battery for at least 5 minutes, then restart and goose it a few times to blow gunk out. Have you reset the hard stop for the throttle valve, you need to use the factory manual on this one, it must be done by the book PERIOD. Another is can be the canister purge, block off the vapor line from the canister to the engine and test drive a while. Let me know what happens if anything

  • yadayada
    yadayada May 11, 2010

    Dis you have codes for all these parts, and each was tested?? quit throwing parts at the isssue and take it in for factory sevice to fix it.

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I had almost the same problem i changed my fuel pump and fuel filter and it worked u mite try that first.

Posted on Feb 10, 2010

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