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Thread: Idle High After Engine Warms Up With Microprocessor controlled idle ECU

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    Member Midnight Specialist's Avatar
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    Question Idle High After Engine Warms Up With Microprocessor controlled idle ECU

    I recently installed Dave's Microprocessor controlled idle ECU and it brings the idle down to 775-800 when I first start the car, but it bumps up to 1000 - 1200 after it warms up. I looked at the LED on the ECU and it's illuminated indicating the idle motor is holding at a full closed position. I attempted to the curb idle screw and I could almost take it out with no change in the RPMs. I thought that it might be the idle motor, but I put a new on in and the same result, still at the 1000 - 1200 RPM range. Anyone have any ideas on what might be causing this issue?

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    Senior Member Bitsyncmaster's Avatar
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    I had the same problem. I could back out the curb idle screw all the way and on a hot engine it idled at 1000 RPM. That turned out to be bad deceleration springs. I bought a used replacement throttle body and that cured that problem.
    Dave M vin 03572
    http://dm-eng.weebly.com/

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    Member Midnight Specialist's Avatar
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    Thanks Dave. Love the ECU so far. Just need to nail down the issue. Going to try the spring like yours.

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    Senior Member Bitsyncmaster's Avatar
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    I had posted a photo of bad springs a long time ago. I will look if it's still here. But if you take off the W pipe, you can see the springs. If they are not evenly spaced then they are the bad ones. The good springs are evenly spaced.

    Found it.
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    Last edited by Bitsyncmaster; 03-24-2021 at 07:47 PM.
    Dave M vin 03572
    http://dm-eng.weebly.com/

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    Administrator Ron's Avatar
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    Quote Originally Posted by Midnight Specialist View Post
    I recently installed Dave's Microprocessor controlled idle ECU and it brings the idle down to 775-800 when I first start the car, but it bumps up to 1000 - 1200 after it warms up. I looked at the LED on the ECU and it's illuminated indicating the idle motor is holding at a full closed position. I attempted to the curb idle screw and I could almost take it out with no change in the RPMs. I thought that it might be the idle motor, but I put a new on in and the same result, still at the 1000 - 1200 RPM range. Anyone have any ideas on what might be causing this issue?
    Did you ever find a solution to this? I'm finding I have the same problem. I sometimes find if I let put the clutch a but w the brake still applied it'll sometimes bring my rpms down a couple hundred while at a stop.

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