Idle issues

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Dec 28, 2009 | 01:50 AM

1992_f150

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Idle issues

Hey.
So i got a 1992 F150 5.0L (302) 2WD and for about a week now ive been having issues with the high idle. when i start the truck it starts fine and it goes to about 1000RPM's then a few seconds later the RPMs will drop and the truck will stall out if i dont keep my foot into it. then when the truck warms up the idle will return to normal (about 500 RPMs) but anytime after that when i start the truck it runs fine other that a rough idle. could it be moisture in the gas lines? or the fuel filter or battery? any help or ideas would be greatly appreciated.

Thanks for your time.

Jon

Dec 28, 2009 | 03:45 AM

Lazy K

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I think, if it was me, I would start by looking for any stored trouble codes. If you don`t have a code reader you can go to fordfuelinjection.com and from the list on the right, click on self test for instructions on how to do it without one.

Dec 28, 2009 | 09:10 PM

rla2005

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I agree start by looking for stored codes. Then go from there. Most common failure item with no stored codes is the Idle Air Controller (IAC). It can gum up with carbon deposits. You can ry cleaning it, but most find replacing it works best. Start with codes, then move on from there.

Dec 30, 2009 | 07:27 PM

86Redline

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Mine does the same. 1988 F150 6cyl manual. Starts fine, idles a few seconds (haven't paid attention to the RPMs) and then stalls. I have to play this game with it about 2-3 more times before it stays running. During the 2nd or 3rd attempt, if I stay off the gas, the idle is sporadic. It'll idle up, then down, and so on. After warmed up and for any further driving, restarting from say a visit to the store, it's fine. It's just this initial cold start.

I don't mean to bogart the original post, but can someone with a similar year please shoot me pics of where these two are located? Or describe the location here?

This issue isn't major - I could live with it - but would really enjoy the chance to resolve it. My apologies to the original poster for throwing my issue in here.

Dec 31, 2009 | 04:00 AM

Lazy K

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Redline, the Idle Air Control valve and the Throttle Position Sensor are both on the throttle body (under the air filter). Go to fordfuelinjection.com and click on each one for pics and how to test.
Also, from the list on the right on that site, click on Self Test and it will tell you how to pull any stored trouble codes.

Dec 31, 2009 | 09:27 PM

86Redline

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Thanks a million Lazy K! I seem to work best with pics. That site you suggested helped. Found both in 5 minutes tonight.

I tried the tapping method first to loosen the carbon. It seemed to make a difference. Truck started and stayed running on the 2nd turn this time... for longer than normal with no sporadic idle. So I ran out & bought a Napa brand replacement. Sadly, it doesn't seem to be the true cause b/c after the swap, waiting an hour to restart, it still does the same thing. Not quite as bad tho. With 293K miles on the truck when I bought it, I don't mind the $60 replacement just for the fact of knowing it's new and ruling out the IAC. (I also edited my original post - shortened it. I can be a bit chatty when I type. Sorry.)

Jan 1, 2010 | 04:01 AM

Lazy K

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How long since a basic tuneup of plugs, fuel and air filters, maybe plug wires and PCV valve? It is sometimes better to do the basics first.
Can also be helpful to check for trouble codes as the computer might know what is wrong or can narrow the problem down.