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Thread: Hanging high idle

  1. #1
    Junior Member
    Join Date:  Jul 2011

    Posts:    16

    Hanging high idle

    I'm having an issue with a hanging high idle, at or around 1500rpm. One day the car was idleing fine and then the next I get this high idle. The car will start fine, needs no gas to start. Will idle at roughly 800rpm. As the temperature increases so does the idle speed. I cant seem to find any vacuum leaks that would cause this. New o2 sensor. Verified resistance to the thermistor both cold and hot. Verified voltage to the idle microswitch. Running in the garage the car smells very rich. Any ideas are much appreciated.

    Sent from my SM-G996U using Tapatalk

  2. #2
    Senior Member r00b's Avatar
    Join Date:  May 2011

    Location:  Co

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    My VIN:    2245

    Check if the idle speed motor is stuck.

  3. #3
    Senior Member
    Join Date:  Aug 2018

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    In my experience, a weird idle problem combined with excess fuel in exhaust was a frequency valve issue, which was eventually traced back to a problem in the Lambda circuit. See if the problem goes away when you unplug the O2 sensor.

  4. #4
    Junior Member
    Join Date:  Jul 2011

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    So I was just thinking. How loud should the frequency valve buzz? Because I don't recall hearing a noticeable buzz sound

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  5. #5
    Senior Member Bitsyncmaster's Avatar
    Join Date:  May 2011

    Location:  Leonardtown, MD

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    My VIN:    03572

    Quote Originally Posted by camaro430sut View Post
    So I was just thinking. How loud should the frequency valve buzz? Because I don't recall hearing a noticeable buzz sound

    Sent from my SM-G996U using Tapatalk
    If you jump the double yellow/red wires to the brown wire on the RPM relay connector you will power the Lambda system without the engine running. Then it is easy to hear the FV buzz. I do that if I want to drop the rest pressure. Just leave it powered for about 60 seconds and rest pressure drops to zero.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  6. #6
    Junior Member
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    I'll have to give it a go

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  7. #7
    Senior Member
    Join Date:  Aug 2018

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    Quote Originally Posted by camaro430sut View Post
    So I was just thinking. How loud should the frequency valve buzz? Because I don't recall hearing a noticeable buzz sound

    Sent from my SM-G996U using Tapatalk
    Its very difficult to hear it when the engine is running. I usually check its operation by feeling it vibrate. To do that though, youd need to be familiar with how it vibrates when it is operating normally.

  8. #8
    Junior Member
    Join Date:  Jul 2011

    Posts:    16

    I'll have to start it up later and feel it.

    If I drive the car the idle with clutch in coming to a stop will hang as high as 2k. Typically 15/1700. With a load from the a/c it will bring the idle to about 1k/1200

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  9. #9
    Junior Member
    Join Date:  Jul 2011

    Posts:    16

    Any chance this could be cause by the deceleration valves?

    Also, I have new o rings and will be cleaning up the previous hacks rtv job

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  10. #10
    Junior Member
    Join Date:  Apr 2013

    Location:  Warwickshire UK

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    Quote Originally Posted by camaro430sut View Post
    I'll have to start it up later and feel it.

    If I drive the car the idle with clutch in coming to a stop will hang as high as 2k. Typically 15/1700. With a load from the a/c it will bring the idle to about 1k/1200

    Sent from my SM-G996U using Tapatalk
    I have the exact same issue, idles at 2k when it's warm. If I blip the throttle it drops back to 800. Found out the throttle linkage was out but now wondering if it's the air bypass motors sticking as well.

    Sent from my SM-N950F using Tapatalk

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