Carb expert needed
Thread Starter
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Senior User
Joined: Aug 2007
Posts: 136
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Carb expert needed
Hey all, I am fighting an extremely rough idling gremlin. From partial throttle to wide open my 6cyl runs good but once up to temp (choke fully open) I have to feather the throttle to keep it running. So far I have replaced cap/rotor, plugs, fuel filter and pump and rebuilt the carb.
Am I barking up the wrong tree in thinking it's an air/fuel issue at idle or more like an airleak somewhere? Is the air/mixture screw the only way to richen up the idle mode or is there something else I can tweek?
Am I barking up the wrong tree in thinking it's an air/fuel issue at idle or more like an airleak somewhere? Is the air/mixture screw the only way to richen up the idle mode or is there something else I can tweek?
Hotshot
Joined: Oct 2002
Posts: 18,488
Likes: 22
From: The Big, Oregon
Make sure the carb hasn't worked loose. They liked to do that, especially the Ford Model 1 carbs on the earlier 300-6. The Carter wasn't as bad as that or the Autolite/Motorcraft carbs, but still did it.
What year is your truck, and does it have power brakes, a/c, EGR, etc?
What year is your truck, and does it have power brakes, a/c, EGR, etc?
Thread Starter
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Senior User
Joined: Aug 2007
Posts: 136
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Yep, I've had the carb work loose alittle in the past but it's plenty tight now and yes it has power brakes. It just seems like it's a lean at idle problem cause when after the choke opens fully the idle goes to crap. Is there a way the richen up the idle circuit on these carbs?
Posting Guru
Joined: Apr 2003
Posts: 1,153
Likes: 1
From: Venezuela
Yea sounds like lean hot idle condition.
The main control for fuel delivered is the fuel level at bowl. Then the mixture screw.
Check/adjust float level, clean all internal passages at carb body. I'm assuming there are no vacuum leaks, remember, carburetor delivered proper fuel amount ONLY for air passing through its barrel
The main control for fuel delivered is the fuel level at bowl. Then the mixture screw.
Check/adjust float level, clean all internal passages at carb body. I'm assuming there are no vacuum leaks, remember, carburetor delivered proper fuel amount ONLY for air passing through its barrel
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Lead Driver
Joined: Feb 2002
Posts: 7,955
Likes: 591
From: Greater Austin, Texas
Sometimes the body will get loose from the base, you gotta check that too. Sounds like a vac leak of some kind to me.
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Senior User
Joined: Jul 2004
Posts: 141
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From: Il.
With throttle off idle slowly close choke plate, any improvement in idle indicates vacuum leak or carb problem.
Check for vacuum leak by spraying cheap carb cleaner spray around all gaskets and vacuum lines and look for improvment in idle. pinch off any vacum lines in question and look for same results. Good Luck
Check for vacuum leak by spraying cheap carb cleaner spray around all gaskets and vacuum lines and look for improvment in idle. pinch off any vacum lines in question and look for same results. Good Luck