My 1992 F150 has had this problem for awhile where it wants to idle very high. When I say high I mean at least 2000 rpm. It only does it from time to time though. Its not every day but it is very annoying. I was told it may be a vacuum leak but Ive checked with carb and choke cleaner and never found anything. I also don't think it would come and go if that was the case but I don't know? I do know that if I unplug the idle air control valve while its doing this the idle will drop to normal. Other than that I'm at a loss.
92 F150 idling high
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Have you taken the idle air control valve off and looked at the inside? If I was going to bet on a culprit, that would be it...
I had this problem once on my Aerostar. It was the TPS (Throttle Position Sensor).
Have you checked for codes? Don't start replacing sensors because someone says so without further testing. I think you ruled out a binding, carboned up AIC solenoid/ pintle because the idle would not have dropped by unplugging the solenoid connector.
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Originally Posted By: oldmaninsc
I had this problem once on my Aerostar. It was the TPS (Throttle Position Sensor).
Yep common problem on OBD-I Fords...
If it isn't setting a TPS code, adjusting TPS voltage will likely fix it, plenty of info on how to properly set them... Note it may not be factory adjustable, elongating mounting holes is the solution(some models had factory adj TPS others did not)...
Also note the 5.0 & 5.8 truck intakes make it a [censored] to access TPS... I've removed the throttle body to make adjustments(electrical connector remains connected)...
I had this problem once on my Aerostar. It was the TPS (Throttle Position Sensor).
Yep common problem on OBD-I Fords...
If it isn't setting a TPS code, adjusting TPS voltage will likely fix it, plenty of info on how to properly set them... Note it may not be factory adjustable, elongating mounting holes is the solution(some models had factory adj TPS others did not)...
Also note the 5.0 & 5.8 truck intakes make it a [censored] to access TPS... I've removed the throttle body to make adjustments(electrical connector remains connected)...
Yup. Dirty/sticking IAC, TP sensor not showing correct idle voltage, ECT/circuit reading cold, or vac leak.
Pull codes first before anything else.
http://www.thorssell.net/hbook/eectest.html
Ignore the test light and meter hookup. The MIL on the dash will flash the codes, if any. Key off, Jumper connector as shown, turn key to run position (don't start it), count the flashes.
Pull codes first before anything else.
http://www.thorssell.net/hbook/eectest.html
Ignore the test light and meter hookup. The MIL on the dash will flash the codes, if any. Key off, Jumper connector as shown, turn key to run position (don't start it), count the flashes.
Throttle position sensor is my guess. Sometimes it takes more than one to get a good one too.
If I recall correctly, at voltages above 1.1v, the computer thinks the throttle is part way open and cranks the IACV open to "catch" the engine when the throttle is cut, to gently bring the RPM back down.
Back probe the TPS wires and look for it's output voltage. should be somewhere south of 1v. I think spec is .6v to .95v?
If I recall correctly, at voltages above 1.1v, the computer thinks the throttle is part way open and cranks the IACV open to "catch" the engine when the throttle is cut, to gently bring the RPM back down.
Back probe the TPS wires and look for it's output voltage. should be somewhere south of 1v. I think spec is .6v to .95v?
http://oldfuelinjection.packrad.net/page85.html
I'm not sure if the 5.8 has these but doing this on my 1990 Mustang fixed the annoying high idle.
I'm not sure if the 5.8 has these but doing this on my 1990 Mustang fixed the annoying high idle.
IAC, TPS, and vacuum leaks come to mind here. Are there any codes? Vacuum leaks can be tricky, did you have it smoke tested?
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