idle problems
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Fleet Mechanic
Joined: Aug 2002
Posts: 1,568
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From: Swansea SC
idle problems
When motoring along trucks runs good , when stopping occasionally it is slow to return to idle -start/stop fast ,seems it takes 20 seconds to return to normal idle . Of course this doesnt happen all the time (75% mabey )Any clues to what my problem is all replies appreciated TR
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From: Virginia
Which truck is this? I will assume it's the 85 since you are in this forum. When you have this problem, I would get out, take the aircleaner off, and make sure the choke door on top of the carb is straight up and down. If it's at an angle, and kind of loose, I would take the black round choke housing on the side of the carb, and turn it a little toward the "leaner" direction till the choke door stands straight up. Mark the housing first before you move it.
Last edited by Franklin2; Dec 27, 2003 at 10:04 AM.
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Joined: Jan 2001
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From: Nebraska
If it's not something mechanical in the carb hanging up, it's computer related (I'm assuming you have the EEC-IV feedback carb.) There is a motor on the back side of the carb that extends and retracts to control the idle speed. Make sure your idle is set according to the emission sticker under the hood. If that doesn't help you can pull the codes and see what that gives you.
My truck does the same thing and about the only thing I haven't tried is a new computer. You can't just unplug the ISC motor or your truck will run like crap. If you have just the "extend" wire unplugged it will be hard to start and won't idle cold. What I did was wire a toggle switch in the cab to the idle speed control motor extend signal wire. This way I can have it on for startup so I have a nice high idle when it's cold. Then when it warms up and finally idles down, I flip the switch off and the idle will stay down.
My truck does the same thing and about the only thing I haven't tried is a new computer. You can't just unplug the ISC motor or your truck will run like crap. If you have just the "extend" wire unplugged it will be hard to start and won't idle cold. What I did was wire a toggle switch in the cab to the idle speed control motor extend signal wire. This way I can have it on for startup so I have a nice high idle when it's cold. Then when it warms up and finally idles down, I flip the switch off and the idle will stay down.
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Fleet Mechanic
Joined: Aug 2002
Posts: 1,568
Likes: 33
From: Swansea SC
idle
I appreciate the replies, Franklin its the f-150 300cc 4x4 single (1985)carb( feed back) and i have ran it w/out the air cleaner . Things ive replaced idle speed controller, temperator sensor, throttle position sensor and its slowed it down a bit .Before all these things were changed i installed a 192 degree thermostat . I feel that might of been the culprit, why?when changing it out 160degree was stuck open PERMANTLY , truck never idled high at all, i replaced the 192 back with a new 160 and get the high idle when my gauge reads half way on the temp gauge .When this occurs i get a longer high idle. In running it (even with the 160) and its (half way) longer idle. Thermostat open low scale idles fine.When i had the 192 it stayed half way on the gauge, all the time and idle return was triple that.Now if i creep around in the truck (NEW 160 degree)2 or 3rd gear its not open (thermostat) (high idle) then opens, it idles fine .Now this truck has over 400,000 miles on it and on its second carb Any one have this problem?Ive read on a search that the clutch on my fan might be shot if u can move it when truck is off ? true or false thanks TR------
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