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Carburetor Problem?
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DarkAzura



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    Post: #1
    question Carburetor Problem?

    Whenever I start up my car it idles high because I have to pump the gas for it to start. Aside from starting it, if I rev the engine it will idle even higher which leads me to believe something is sticking or getting stuck. The only way I can lower the rpm is by pumping the gas and hoping it drops down to the normal rpm.
    Is my carburetor to blame and does the cold weather play a part?
    Away 01-11-2011 05:25 PM
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    72HCODE


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      Post: #2
      RE: Carburetor Problem?

      Well a few things here

      1) do you have the original carb on the engine or an aftermarket carb?

      2) do you have a choke on your carb?

      3) have you checked the throttle linkage by itself to make sure it's not binding on anything and moves freely from idle to WOT?

      Let's say you checked the linkage and discover nothing is binding:

      If you have a choke check it's settings, is it fully opening when warmed up?

      Depending on what carb you have you may have the option of a startup idle setting.
      This is a lever usually connected to the choke, that forces the base idle Rpms up until the choke is fully disengaged. This helps during a cold start and while the engine is warming up to prevent misfires and stalling and acceleration issues. This is why you want to make sure the choke is working correctly.

      Let's say you found no problems with the linkage , and your choke is working correctly and it is set correctly and the problem is still there.

      You may have a vacuum leak somewhere, look around for any vacuum lines that may have popped off, you can try placing your hands over the carb when the engine is running and try to stall it by choking off incoming air. If you totally close off the intake to the carb and the engine is still running then you know the engine is pulling in extra air from somewhere else which is increasing engine Rpms.

      Now you could also have a sticking vacuum advance or a sticking mechanical advance in the distributor.

      First I would look for a mechanical issue.

      Disconnect the throttle cable to the carb, move the butterfly by hand rev the carb from the engine bay, and make sure idle returns back to normal feel for any sticking when you move the throttle lever.

      Next check the accelerator pedal for any sticking, there is a large return spring built into the throttle cable make sure the spring isn't broken or collapsed and the pedal returns to the correct hieght inside the car.

      Inspect your choke make sure its not sticking or out of adjustment.
      Make sure it fully opens when the engine is at tempature.

      Check the issue with the thottle when the engine is warmed up if it goes away then it could be the choke.

      Once you ruled out any mechanical binding of the throttle then move on to more radical things.

      Checking the movement of the throttle by hand and feeling for any binding is important, it could be as easy as the butterflies getting hung up on the air intake, and just loosing the mounting bolts for the carb and jiggle the base so you have free movement.

      After mechanical things binding start checking for vacuum leaks.

      If you find the linkage always returns to the same position and you can't find or hear any vacuum leaks, then hook up a timing light and inspect the base Timing of the motor, if it changes by the throttle position does not then suspect an issue in the distributor.

      Post some feedback on what you tried and what happened.
      Offline 01-11-2011 06:16 PM
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      DarkAzura



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        Post: #3
        RE: Carburetor Problem?

        Thanks for the reply 72HCode. Sorry for such a late reply, I've been busy and haven't had a time to check out the carb. Just letting you know I appreciate the advice and will put it to use when I get a chance Smile
        Away 01-16-2011 11:09 PM
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