85 supra revs at 2000rpm can't figure out why help please! - Page 2

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  1. #11
    CelicaSupra.com Member supraz's Avatar
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    The idle screw really isn't an idle speed adjustment screw at all and generally should not be touched. The idle speed is totally controlled by the ECU through the ISC valve. It sets the engine speed it wants.

    When my ECU had a bad driver so it could not alter the ISC setting, I had set the ISC valve manually so that the idle speed was really high. Rather than letting the engine speed run away, the ECU was somehow dropping the idle speed by some other technique; I suspect that it was adjusting ignition timing to do this. The result was the engine rpm cycling from 1000-2000 rpm like what you are describing.

    It sounds like you still have an air leak into the intake plenum, or the ISC valve is stuck too far open
    Black 1983 P Type 5 Spd, Cloth Interior, BBK,HRE 17" Wheels, HKS Exhaust
    White 1984 P Type Auto, Leather Interior, Sunroof, Digital Dash

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  3. #12
    CelicaSupra.com Member supraz's Avatar
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    This is the sound of the ISC valve


    The image of the video is meaningless, but you can hear at the end the sound of an oil can being pumped. This is the ISC valve being opened.
    If you don't hear this sound, the ISC valve is frozen, or the ECU/wiring is faulty.
    This happens every time you turn your engine off.

    When you start the engine, there will be enough air for the engine to catch and the ECU is able to step the ISC valve down quickly enough to prevent the engine rpm from racing.

    Dale
    Black 1983 P Type 5 Spd, Cloth Interior, BBK,HRE 17" Wheels, HKS Exhaust
    White 1984 P Type Auto, Leather Interior, Sunroof, Digital Dash

  4. #13
    Founding Member pdupler's Avatar
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    Quote Originally Posted by supraz View Post
    The result was the engine rpm cycling from 1000-2000 rpm like what you are describing.
    Actually a classic symptom of a TPS out of whack too.
    Phil D.
    85 Silver 6m-gte, completed 2000

    "I always observe the speed limit. I see those DAMNED signs everywhere."

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  6. #14
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    Quote Originally Posted by pdupler View Post
    Actually a classic symptom of a TPS out of whack too.
    I did receive calibrate it as per TSRM says to do so wonder if it's just faulty? Everything's was reading within spec though as well

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