Gordini 804 engine idling
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  1. #1
    Fellow Frogger!
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    Default Gordini 804 engine idling

    Can anyone suggest why my 1100cc engine (with twin 40mm Webers ) idles too fast? I have backed the throttle stop screw off, so it doesn't even touch, the ignition has been set with a timing light and even retarded a bit to slow revs down, and the idle mixture screws (4 )are open approximately 11/4 turns. Is there something else ? I can sometimes have it idling at say 800-1000rpm, however as soon as I drive the car it sits on about 1500rpm. I have checked and re-bushed the throttle linkage but still the problem persists.

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  2. #2
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    Try spraying some non flammable liquid or similar on the inlet manifold gaskets and around throttle shafts with engine running to check for leaks.You should see a change in revs if there is a leak.Cheers Brian

  3. #3
    1000+ Posts robmac's Avatar
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    I agree, it's likely to be either an induction leak or throttle butterflys not sealing properly/ or fully closing.

    Suspect the butterfly linkage too they could be improperly synced. And one holding the other open.

  4. #4
    1000+ Posts renault8&10's Avatar
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    Agree with the leak test, but other things to check are the butterfly shafts binding; nut too tight.
    It is also possible to bend the butterflies so they don't seal properly (twist in the shaft) if you used WOT on the butterflies to tighten the side nuts.

    Of course carby balance could also be a cause.
    KB


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    Is there slack on the the accelerator cable?

    if you can push the linkage such that the car returns to a reasonable idle then I that's a lead.

    You mentioned the spindles were rebushed. Did they turn freely before installation? Any hint the the butterflies were sticking?
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  6. #6
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    Using the palm of your hand to seal off each carby throat in turn is a quick way
    of seeing how it affects idle and narrowing down where the problem may be.
    The old hose in the ear technique checking the sound of each butterfly helps too.
    Look for air leaks as previously suggested.
    Check your brake booster, block the vac hose for any difference, etc.
    Correct distributor? vac module?
    Original 1100's had Solexes.
    With the Webers fitted are the linkages central between the two? or separate
    pushrods? If they are not accurately synchronised and free to move, one carby
    can end up preventing the other carb butterfly closing fully.

  7. #7
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    Quote Originally Posted by robmac View Post
    I agree, it's likely to be either an induction leak or throttle butterflys not sealing properly/ or fully closing.

    Suspect the butterfly linkage too they could be improperly synced. And one holding the other open.
    Thanks for all the helpful replies, I'll go through the remedies one by one during the weekend.

  8. #8
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    Quote Originally Posted by Steve K View Post
    Using the palm of your hand to seal off each carby throat in turn is a quick way
    of seeing how it affects idle and narrowing down where the problem may be.
    The old hose in the ear technique checking the sound of each butterfly helps too.
    Look for air leaks as previously suggested.
    Check your brake booster, block the vac hose for any difference, etc.
    Correct distributor? vac module?
    Original 1100's had Solexes.
    With the Webers fitted are the linkages central between the two? or separate
    pushrods? If they are not accurately synchronised and free to move, one carby
    can end up preventing the other carb butterfly closing fully.
    Hi Chris,
    A lot of good suggestions here. I would never recommend using the palm of you hand though. A bad habit that may cause damage in other circumstances. If you want to try it then use a piece of board or similar.
    The piece of tubing in the ear is very good practice and I used that just the other day for listening to a noise in someones' diesel. Excellent for listening to the throats of multi carbies for setting the idle screws, or in your case checking for one carby carrying the load. Just a length of fuel tubing or the like will do nicely.
    Jaahn

  9. #9
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    Quote Originally Posted by jaahn View Post
    Hi Chris,
    A lot of good suggestions here. I would never recommend using the palm of you hand though. A bad habit that may cause damage in other circumstances. If you want to try it then use a piece of board or similar.
    The piece of tubing in the ear is very good practice and I used that just the other day for listening to a noise in someones' diesel. Excellent for listening to the throats of multi carbies for setting the idle screws, or in your case checking for one carby carrying the load. Just a length of fuel tubing or the like will do nicely.
    Jaahn
    Thanks Jaahn, I'll try that also over the weekend.

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