IAC cleaning
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Senior User
Joined: May 2010
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IAC cleaning
I know this has been covered a million times, but I never have luck with searches.
Idle jumps up after like 10 min of driving, it's the IAC right?
What's the best way to clean the IAC? I couldn't find carb cleaner at walmart earlier. Anything i can sub in and clean it with?
Idle jumps up after like 10 min of driving, it's the IAC right?
What's the best way to clean the IAC? I couldn't find carb cleaner at walmart earlier. Anything i can sub in and clean it with?
Tuned
Joined: Aug 2007
Posts: 287
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I had the same issue. I tried cleaning and the replacing the IAC. Still had intermittent hight idle. what it turned out to be was the TPS. The old TPS (Ford brand) wasn't even 18 months old but it had developed a symptom of increasing the output voltage from .09 to 1.05 after the engine got hot. I even tired setting the TPS at .085 to compensate but then I got a "TPS out of self test range" code. The high idle was totally annoying and drove me nuts. I finally picked up a Advance Auto TPS and that was that.
To confirm my theory I bench tested the old TPS by using a heat gun with a meat thermometer in the air stream laying next to the TPS and a digital voltmeter. Sure enough as the temperature increased to 200 degrees the resistance in the TPS would go up. When the TPS cooled down the resistance would return to normal.
It only takes a tenth of a volt variation to increase the idle speed. On my 1988 F250 351 the TPS gets rippin hot as it sits on the bottom of the throttle body. Poor design placement - IMO. Would be nice if it had been situated in some cooler location like a refrigerator.
To confirm my theory I bench tested the old TPS by using a heat gun with a meat thermometer in the air stream laying next to the TPS and a digital voltmeter. Sure enough as the temperature increased to 200 degrees the resistance in the TPS would go up. When the TPS cooled down the resistance would return to normal.
It only takes a tenth of a volt variation to increase the idle speed. On my 1988 F250 351 the TPS gets rippin hot as it sits on the bottom of the throttle body. Poor design placement - IMO. Would be nice if it had been situated in some cooler location like a refrigerator.
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I think that's where mine is too. Does anyone have a diagram that shows where it is on a 92 302?
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Tuned
Joined: Aug 2007
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To the best of of knowledge the IAC doesn't send any info to the computer. It only receives electrical pulse input from the computer based on the input the computer has received from the various sensors -TPS, ECT, ACT, MAP etc.
Der Postmeister
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From: Long Beach, Calimexiforia
Posting Guru
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From: North Reading Mass
Thanks for getting back to us Kentuckyredneck. In HVAC/R we use a lot of solenoid valves. Although very dependable they can fail but many times its because something else is faulty which causes the failure. Anything that restricts the valve from full travel (gunk) or low voltage can shorten its life. Its an actuator that is controlled by the computer but it doesn't give any info back. As pointed out in the links a careful cleaning will help but may not restore a valve that is completely gummed up.
Great info on those links
Thanks to all who posted.
regards
rikard
Great info on those links
Thanks to all who posted.
regards
rikard