high idle when warm 8v gti

Discussion in '8-valve' started by eddiedebo, Feb 13, 2021.

  1. rubjonny

    rubjonny Administrator Staff Member Admin

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    the idle switch bracket should be set so it just clicks when throttle hits the stop, if you move it too far in it'll lift the throttle off the stop. if you suspect the throttle stop has been messed with that can also be adjusted. adjust the stop till it comes away from the throttle, tighten it again till it just makes contact then go a further half turn. obv loosen the idle switch right off before doing this to make sure its not throwing anything out
     
  2. eddiedebo Forum Member

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    thanks Jonny really appreciate it. Throttle stop has definitely been moved in the past.

    I'll give all this a try and report back!
     
  3. eddiedebo Forum Member

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    I hooked up the timing light and it appeared to be out by quite a bit. Which was surprising as it seemed like everything was pretty close now. So I've reset the dizzy advance.

    Then loosened the idle switch and throttle stop to allow fully closed throttle. Then turned it back half a turn and tightened the throttle stop then the idle switch.

    I've gone to set the base idle, removed the blue temp sensor and it runs so rough it will hardly rev over 2k.

    It's almost as though the timing was actually closer before despite the timing light suggesting it was out.

    I don't know what I did wrong this time but I think I'll have to check the timing again.
     
  4. Tristan Forum Junkie

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    Any chance you would be looking at the wrong mark on the flywheel?
     
  5. eddiedebo Forum Member

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    I don't think so as I have marked only the big timing mark. So the the smaller timing mark isn't really visible with the timing light.

    I was in a bit of a rush so I'll check it all again tomorrow when I have more time. Also because of this the engine wasn't upto temp but I'm not sure if that makes a big difference.
     
  6. Tristan Forum Junkie

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    Is it a notch,/line, or a diamond you're looking at?
     
  7. eddiedebo Forum Member

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    It's a diamond the 6 degree BTDC mark
     
  8. davkav

    davkav Paid Member Paid Member

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    The man speaketh the truth. The timing marks on my flywheel were all wrong. I had to use the marks on the drive belt pulley on the crank.
    It would be worth checking the pulley TDC marks align with the flywheel marks.
     
  9. eddiedebo Forum Member

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    I've timed it this way at least 5 times in the past and it's at least been close to correct if not correct. This time it's way out
     
  10. eddiedebo Forum Member

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    So I've reset the timing this morning. Not sure what I did wrong the last time but it seems correct now.

    What I've discovered is when setting the base idle if I adjust the idle screw just slightly too far, then after plugging the blue sensor back in and revving the idle will seem to stick to 1100rpm. If I knock the idle screw back a touch then it will settle back to the correct idle I have set.

    The problem is to stop the idle sticking at 1100rpm I have to set the idle slightly too low.

    Is this normal behaviour?

    I'm setting the idle following Jonny's guide. Remove the blue sensor, rev 2.5k 3 times and then adjust. Plug the sensor back in
     
    Last edited: Mar 6, 2021
  11. rubjonny

    rubjonny Administrator Staff Member Admin

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    are you using the digital rev counter? the needle might be a little off. but tbh, if it runs and idles fine where you've set it I wouldn't be worried
     
  12. eddiedebo Forum Member

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    No my MFA screen needs replacing.

    But it's not that the numbers on the rev counter aren't exactly right. It's more that once the heater and lights are on then its borderline. It's just about ok.

    I would ideally have the the idle just a touch higher. But I cant because if I adjust it any higher it will start sticking at 1100-1200rpm.
     
  13. rubjonny

    rubjonny Administrator Staff Member Admin

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    is the engien struggling when those are on? perhaps the isv isnt working so well so ecu is struggling. mk3 golf 2e ones work and slightly newer, though these days they're al still pretty old and hard to find :lol:
     
  14. eddiedebo Forum Member

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    The rpm drops enough that the engine does struggle. If the idle was any lower it would be stalling.

    The ISV doesn't buzz as is described in other posts. I've always assumed it is working as when I plug my spare ISV in the car just doesn't run.

    But maybe I could try cleaning it out.

    Just to add the idle does float up and down a touch also. Nothing dramatic but it's noticeable.
     
  15. rubjonny

    rubjonny Administrator Staff Member Admin

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    it should definitely buzz or at least be felt to vibrate with ignition on, if nothing then its stuffed or you have a wiring fault
     
  16. eddiedebo Forum Member

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    ok I can confirm 100% it doesn't buzz or be felt to vibrate with ignition on.

    I'll look into getting that sorted.
     
  17. eddiedebo Forum Member

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    I got hold of another ISV which was tested by Brendon at Dubstock.

    I still have no buzzing or vibration from the new ISV. In fact if I disconnect it there's no obvious difference.

    Wiring visually looks fine. Does anyone have any tips for testing the isv? If I remove the hoses with power connected should I see movement of the motor inside?
     
    Last edited: Mar 20, 2021
  18. davkav

    davkav Paid Member Paid Member

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    If you can't hear/feel it buzzing, it must not be getting power. Check the plug and make sure all the contacts are clean.

    Failing that, if you do a continuity test between pins 22 and 23 on the ECU connector and the plug for the ISV that will tell you if there is a break in the wires somewhere.

    Link to ECU pinout.
     
    Last edited: Mar 20, 2021
  19. eddiedebo Forum Member

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    Thanks for that I have continuity to both pins. So the wiring at least is fine..

    What condition needs to be met for the isv to function? Is it the idle switch?

    I have already replaced the switch but maybe it's still not working. I just tried holding revs at 1.5k and pressing the wot switch and nothing happened.
     
    Last edited: Mar 20, 2021
  20. rubjonny

    rubjonny Administrator Staff Member Admin

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    sounds like ecu is stuffed to me
     

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