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post #1 of (permalink) Old 06-04-2001, 09:24 AM Thread Starter
 
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carb experts needed

I am trying to tweek up my holley carb. I just put it on the jeep a little while back and it seems like it wants to run at very high rpms and not step down when warmed up. I have tried disconnecting the choke, but it still runs high. I have also tried turning the idle screw (I think its the idle screw, the screw that adjust the throttle mechanism.) I have a holley carb book, but they don't tell me much about this particular case. any help is appreciated

Jay

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post #2 of (permalink) Old 06-04-2001, 10:17 AM
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Re: carb experts needed

I'm kinda reluctant to reply to this question because I'm not a Carb Expert. You haven't elaborated on what you done to troubleshoot this problem. Here's my .02: There could be a variety of situations which may cause too high an idle after it warms up and the most likely IMHO is a vacume leak. You can try the common method of looking for the leak by spraying staring fluid or ? until you hear a noticable chang in the RPMs. Another cause might be a mechanical, ie, where the throttle plate is not closing enough, either the linkage hitting the stop screw, cable binding or by the plates hitting a gasket or adapter plate. The ckoke is unlikely because you can visiually see if the choke opens totally or not and it would run like doo-doo if it stayed shut. Oh, and your timing could be advanced too far, but changing a carb wouldn'd likely affect timing. These are just some of the obvious things that come to mind quickly, hopefully a Carb Expert will give some help too.

post #3 of (permalink) Old 06-04-2001, 11:08 AM
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Re: carb experts needed

Does all the carb mechanism move freely, with no binding that would prohibit it from returning to idle easily?

Do you have the mixture set properly? Try leaning it out a bit and see what the RPMs do.

With the engine off, have someone floor the throttle and hold it. Does the butterfly open up straight up and down? What do the butterflies look like with the pedal released? Does adjusting the idle screw change their position?

How did you "disconnect" the choke? Is the choke plate fully 'retracted' to a position where it isn't blocking airflow? If not, move it manually (very carefully, don't break it) to a fully vertical position.

I would guess that your problem lies either in the choke not being fully off...or your mixture being improperly set. If playing with the choke causes the idle to drop, then it is likely the problem. If playing with the mixture screws causes the rpms to drop, then they are likely candidates. If the butterflies don't have a full range of motion with the throttle pedal, then it is possible that your throttle linkage is maladjusted.

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post #4 of (permalink) Old 06-05-2001, 09:41 AM Thread Starter
 
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Re: carb experts needed

Farmjeep,

How do you change the mixture? I know there are screws to do this and I will have to look in my manual.

I have watched the butterflies, and they seem to be functioning properly, closing up all the way. I haven't tried wide open though. It is an electric choke and I disconnected it from power, which released it. The engine doesn't seem to loose power or hesitate at all when I cover the air intake of the carb, mimicking the choke. Does this mean its a vacuum leak?

sorry to be so vague, but I have tried only a few simple things. I am hoping it is fairly simple.

thanks
Jay

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post #5 of (permalink) Old 06-05-2001, 11:24 AM
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Re: carb experts needed

Have you adjusted your curb idle screw? Thats the screw that is on the choke side of the carb not the throttle linkage side. Its upside down and you'll need to do it with the engine off and the throttle pulled open. Try that.

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post #6 of (permalink) Old 06-05-2001, 12:10 PM
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Re: carb experts needed

There is a seperate screw that adjusts the fast idle. It should be near the choke linkage and be very small and hard to see. You might want to pull the carb and check all the specs. That would be easiest.

post #7 of (permalink) Old 06-05-2001, 12:18 PM
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Re: carb experts needed

I'm no 'expert', but unless I'm mistaken, an electric choke that is unplugged will never heat up and open. It will stay choked all the time. Gotta get 12v+ to that choke when the key's on.

Good luck,
Pete

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post #8 of (permalink) Old 06-06-2001, 11:23 PM
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Fast Idle Cam

The fast idle screw rides the edge of a cam which is operated by the choke mechanism (either the electric assist or some combination of heat & vacuum). You have to set the operation of the cam (usually by turning the electric assist housing) and the fast idle speed (by adjusting the screw). All of this should have been in the instructions - if it's not, pester the Holley online techs until they give up the info.

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