Erratic idle when cold
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Joined: Jun 1999
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Erratic idle when cold
My 92 f-150, 302 v-8, has been idling erratically, and even dies when cold. This is in Wisconsin, ranging from +30 to -20. The truck when warm runs fine. idle will bounce from 1200 to 250 and back. Any idea's? I don't know how old the fuel filter is. truck has 140K on it. Thanks
Senior User
Joined: Mar 2000
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Erratic idle when cold
A good place to begin is to clean the throttle body with some throttle body cleaner. It comes in a spray can and can be found at the hardware store. You spray this stuff on the inside the bores while keeping the engine from stalling. You could also remove and clean the idle air control valve.
Guy
'92 F150 XL 4x4, 5.0L AOD, Headers, K&N Air Filter, 3.55 Gears, 31x10.5x15 Tires.
Guy
'92 F150 XL 4x4, 5.0L AOD, Headers, K&N Air Filter, 3.55 Gears, 31x10.5x15 Tires.
Junior User
Joined: Dec 2000
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Erratic idle when cold
Usually the problem is a dirty Idle Air Bypass valve. It is the cylinder on the throttle body with the electrical connector on it. To clean it, first remove the wire clip connected to it and remove the two bolts that hold it to the throttle body. I have never had a gasket break, so that shouldnt be a problem. There are two screws holding the unit together. Remove them and be careful not to lose the O-ring between them. Using spray carburetor cleaner, clean the inside of the mechanical part of the valve. Be especially observant of the small piston. Once all is clean , reassemble and put back on the truck. This valve cycles when cold to increase idle for faster warm ups (as I understand it) and also raises idle speed when the AC or defrost is on. With age, it gums up and doesnt cycle properly. Hope this helps.
89 F150 4x4 300/4 speed 33.12.50 w/Rancho lift 3.55 gears
82 Mustang GT 302 C4 + nitrous=FAST
91 Mustang GT basic bolt ons- GM Eater
89 F150 4x4 300/4 speed 33.12.50 w/Rancho lift 3.55 gears
82 Mustang GT 302 C4 + nitrous=FAST
91 Mustang GT basic bolt ons- GM Eater
Senior User
Joined: Mar 2000
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Erratic idle when cold
but with the idle jumping from 250-1500 I would think its a vacumme leak, get a vacumme gauge and hook it up to the vacumme tree on any of the plugs and see if it holds a vacumme, I'm not sure on the #'s but mine seems to like to run when its just slightly below the green mark on my gauge...when replacing my intakes I didn't seal the lower manifold perfectly, and at low rpms/cold it would idle like it was a big block with a really hot cam, lol
1995 F-150 XL Reg Cab/Bed
http://members.sounddomain.com/blind
5-star rated F-150 (big stereo)
1995 F-150 XL Reg Cab/Bed
http://members.sounddomain.com/blind
5-star rated F-150 (big stereo)
New User
Joined: Nov 2000
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Erratic idle when cold
I agree with the last posting a leaking egr valve gasket caused my truck to " lope ". So, get a vacum guage and connect it to the base of the carburetor. Your idle at vacum should be about 20cm.
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