Rough Idle

Discussion in 'Technical' started by MikeG747, Dec 8, 2005.

  1. MikeG747

    MikeG747 Member

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    My 74 only idles rough with car in gear & foot on brake. In neutral it idles smooth, runs perfect. Put it in gear with foot on brakes & the whole car just shakes. It doesn't matter if your in forward or reverse. Let you foot of the brake & everything is smooth again. Could this be a Transmission or Toque Converter issue.:huh: Any clues appreciated.

    Thanks, Mike:)
     
    MikeG747, Dec 8, 2005
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  2. Ronald Hopkins

    Ronald Hopkins Member

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    Does this car have power brakes. If so check your brake booster it could have a blown diaphragm.
     
    Ronald Hopkins, Dec 8, 2005
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  3. MikeG747

    MikeG747 Member

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    Ron it is Front Disc but no power.
    Thanks, Mike:)
     
    MikeG747, Dec 8, 2005
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  4. igo1090

    igo1090 Member

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    how is it when you drive it on the road?
     
    igo1090, Dec 8, 2005
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  5. MikeG747

    MikeG747 Member

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    Dave it runs perfect at all speeds. It's just that annoying shaking when stopped. Wish I could figure it out.
    Thanks, Mike
     
    MikeG747, Dec 8, 2005
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  6. L50watts

    L50watts Member

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    Mike, Aftermarket Carb? what kind? Also check the torque on the intake manifold.
     
    L50watts, Dec 8, 2005
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  7. MikeG747

    MikeG747 Member

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    Intake is a factory 66 Mustang 4V & the Carb is a 65 Mustang 4100 Autolite.
    Mike
     
    MikeG747, Dec 8, 2005
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  8. ronr11

    ronr11 Member

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    hey mike as you know there is no load out of gear so it will idle smoother ,like ronald said possible vacumn leak
    try carb spray around all the gaskets and the carb area ,if you have a vacumn gauge find a manifold port below throttle plates and ck the vacumn 18-22 also remember the engine could still run at idle and have a cylinder/wire/plug breaking down under a load
     
    ronr11, Dec 9, 2005
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  9. MikeG747

    MikeG747 Member

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    Thanks Ron, I will check those items this weekend.
    Mike:)
     
    MikeG747, Dec 9, 2005
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  10. Jamie Miles

    Jamie Miles the road warrior

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    Adjust the little idle screw in some?
     
    Jamie Miles, Dec 9, 2005
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  11. carnzy's 70 mav

    carnzy's 70 mav Member

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    sounds a lot like a vacuum advance problem...:huh: perhaps...?
     
    carnzy's 70 mav, Dec 10, 2005
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  12. igo1090

    igo1090 Member

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    if u put it in gear and it shakes, bring the rpms up some. does it stop shaking? or keep shaking? might be the power valve is too low for vacuum and is opening when not needed. what is vacuum reading and what rating power valve is in it? i dont recall if these carbs had a power valve, but i think they did. usually a plug or wire breaking down will do it under other loads like out on the road during acceleration.
     
    igo1090, Dec 12, 2005
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  13. MikeG747

    MikeG747 Member

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    Dave with the brake on you can press the accelerator slightly to bring up the rpm's & it will smooth out. I tried increasing the idle speed on carb but that didn't help. I don't know if this carb has a power valve either. I checked the vacuum reading & it fluctuates between 14 & 16. I checked for vacuum leaks & found one between intake & carb. Replaced gasket & fixed that one. Intake is sealed great around heads & block. Any ideas.
    Thanks, Mike
     
    MikeG747, Dec 12, 2005
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  14. NICK DOMINICK

    NICK DOMINICK MCCI Virginia State rep.

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    Air/fuel mixture needs adjusting at the carb.
     
    NICK DOMINICK, Dec 12, 2005
    #14

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