Classic Mustangs (Tech) Technical discussions about the Mustangs of yester-year.

1 fix leads to another problem

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Old 03-07-2011, 02:47 PM
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eZ
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Default 1 fix leads to another problem

So yesterday I bent my gas pedal so that it would have more room to get the carbs butterflies all the way open at wot. It was only getting about 75% open.

Now suddenly my carb will not hold an idle. Im guessing that when I bent my gas pedal it now fully closes the butterfly not letting any air in? Ive messed idle speed screws which seem to do nothing. if I adjust the throotle open a little bit it will idle at 1krpms but then all by itself it will start to climb. it will slowly climb the idle up to 1800. If I try to set the idle at 800-900 rpm it will slowly fall on its face down to 500 rpms and then die.

frustrated.
Dan
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Old 03-07-2011, 03:14 PM
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Gun Jam
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Okay okay

1) Its suppose to have return springs installed that force the butterflies against their stop. So even if the gas pedal and linkage were removed it should idle fine.

** make sure the return spring is installed and it is strong and holds the rotating mechanism against the idle set screw (NOT to be confused with idle mixture screw)

2) Is you throttle stop screw set or even installed? This screw adjust idle RPM by not allowing the butterflies to close past a set point. It physically stops the travel of the butterflies and the butterflies are held against this stop with quite a bit of pressure thanks to the spring mentioned in (1)

** make sure the idle set screw is installed and is touching the rotating mechanism attached to the
butterflies.


If all of this looks okay remove the throttle linkage from the carb and move the rotating mechanism by hand watching the butterflies with engine off. It should move smoothly but have a fair amount of resistance caused by the return springs. Start the engine and see if it runs okay with the pedal removed. Rev engine by hand.

Last edited by Gun Jam; 03-07-2011 at 03:17 PM.
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Old 03-07-2011, 03:14 PM
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buening
 
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The return spring and idle speed screw would be what prevents the butterflies from fully closing. Anotherwords, you should be able to bend you gas pedal to your likings and the idle should not be affected assuming you didn't mess with your idle speed screw. Something else must have happened other than you bending your pedal.

Also, make sure you didn't pop a vacuum hose off of something. A vacuum leak will affect idle
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Old 03-07-2011, 03:32 PM
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eZ
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something internally must of happened. It seems like it it running extremely rich. exhaust has a lot of smoke and when i shut the car off a lot of white smoke coming out of the carb
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Old 03-07-2011, 04:10 PM
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well the front float seemed way too high. I adjusted it down and everything seems to be good now. WTF? Why would the front float suddenly decide to change.

I love this stuff
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Old 03-07-2011, 04:30 PM
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001mustang
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i've seen metal floats leak and cause carb to flood.

i've seen fuel shut off needle valve loose seat seal and allow carb to flood.

have not run across float adjustment that became bent while in the carb.

maybe them duke boys have.
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Old 03-07-2011, 04:45 PM
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eZ
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Originally Posted by 001mustang
i've seen metal floats leak and cause carb to flood.

i've seen fuel shut off needle valve loose seat seal and allow carb to flood.

have not run across float adjustment that became bent while in the carb.

maybe them duke boys have.
Thats funny as hell. I still dvr those episodes
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Old 03-07-2011, 07:31 PM
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noroof66
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Bend the gas pedal back???

Sorry, had to say it.
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Old 03-07-2011, 07:34 PM
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eZ
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yes there was not enough "throw" in the gas pedal. When my foot was mashed to the floor the carb was only open 75%. I couldnt shorten the linkage anymore.
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Old 03-07-2011, 09:53 PM
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Gun Jam
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So is it still fixed?

Probably was dirt in the inlet needle seat but maybe the float really had managed to become unadjusted...Who knows.

-Gun
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