Please help with high idle!
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Joined: Jul 2008
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Please help with high idle!
I have an 86 f250 300inline. i put in a rebuilt the motor and carb. i had trouble with the choke so i put on a manuel choke and took off the electric one. my trouble is that the truck idles at 1000 rpms and i cant get it to go down. there are no vaccum leaks and its bolted down tight( i kno they can come loose and leak at the base). on the right(passenger) side of the carb there is a cylinder with a push rod on it that connects to the linkage, i disconnected this becasue i read that on another thread, that didnt work, i also adjusted this push rod abotu 2 turns with a 1/2 wrench and that brought the idle down to 700 rpms, then i revd it up and the idle went back to 1000. i cant adjust the 2 screws ont eh linkage because of the pushrod, and ive adjusted the fuel ratio screw also.i checked and the choke is open all the way also. the truck runs great adn is responsive, just a high idle. any help will do. thanks!
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
Your fast idle is stuck and needs adjusted. This mechanism keeps the idle raised when the choke is engaged (manual or electric, this part stays regardless what type choke you use). It has two adjustments: fast idle speed, and fast idle index which controls how much time the fast idle stays engaged while the choke is on. The speed is controlled by a screw, and the index is controlled by bending a small rod. The other adjustments you were making were for curb idle (moving the solenoid in and out) and idle fuel mixture (a screw). Curb idle is a different "stage."
These are two pages of a rebuild sheet I scanned in which show the basic adjustment on most forms of Carter 1 barrel carbs. Sorry but the images are kind of large. It shows the figures you need to follow. Specifically you need to look at figures 4 and 9. The only difference with your setup is you have a manual choke, so instead of loosening the choke cap and rotating it like the directions say, you just need to pull the choke shut with your cable. The other figures in the drawings will further help you to understand your carb.
http://users.ece.utexas.edu/~jlabundy/carter1.jpg
http://users.ece.utexas.edu/~jlabundy/carter2.jpg
There was no copyright information on these sheets, so I assume I am free to post them.
These are two pages of a rebuild sheet I scanned in which show the basic adjustment on most forms of Carter 1 barrel carbs. Sorry but the images are kind of large. It shows the figures you need to follow. Specifically you need to look at figures 4 and 9. The only difference with your setup is you have a manual choke, so instead of loosening the choke cap and rotating it like the directions say, you just need to pull the choke shut with your cable. The other figures in the drawings will further help you to understand your carb.
http://users.ece.utexas.edu/~jlabundy/carter1.jpg
http://users.ece.utexas.edu/~jlabundy/carter2.jpg
There was no copyright information on these sheets, so I assume I am free to post them.
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
I'll try and see if I can track them down. I'm not sure if I have the rebuild sheet for that carburetor anymore; if I do I'll have to rescan it. When I posted those photos, I was storing them on my university account. When I finished my degree the university closed my web space. I'll see what I can come up with 
