IAC question

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Nov 7, 2012 | 07:05 PM

MikeB 88

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IAC question

I've replaced the IAC and DPFE on my ranger a couple times due to the racing idle. Vacuum lines have also been replaced. Question is, Can the electrical connector build up a "static build-up" and prevent it from working?

I ask because every couple months or so, my truck's idle will start racing. I'll unplug the IAC when I get home from work, and plug it back in next time I drive the truck. It will then idle just fine for another couple months.

Nov 10, 2012 | 06:51 PM

pawpaw

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From: SW Va

Static charge.....not likely, but did you replace the IAC with an aftermarket, or Motorcraft part????

Nov 10, 2012 | 07:27 PM

MikeB 88

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Quote:

Originally Posted by pawpaw

Static charge.....not likely, but did you replace the IAC with an aftermarket, or Motorcraft part????

Aftermarket, BWD from Advance Auto Parts.

Nov 10, 2012 | 07:53 PM

pawpaw

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From: SW Va

OK thats the brand I'm using & I've had the engine speed run away a couple of times since, just like, but not nearly as often as the OEM IAC was doing before it was replaced.
Strangely it most often happens after coming to a stop after climbing a grade, usually when towing. I just shift to "N" & let the rev limiter deal with the runaway rpm. Once the rev limiter kicks in, the RPM quickly comes under control & drops back to normal. Sometimes it'll take a year or so for it to act out again, so I've come to suspect a computer program problem, or maybe something to do with the speed sensor signal processing, don't really know, just rambling on, because the problem although better, the repacement IAC hasn't totally fixed the problem.

Nov 12, 2012 | 07:59 AM

MikeB 88

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Thanks for the input. I will keep thinking on this for a while. Maybe by unplugging the IAC, it resets the computer for a while??

Nov 12, 2012 | 09:06 AM

pawpaw

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From: SW Va

After a runaway rpm event, do you have a CEL lit, or have you had the computer scanned for set, or pending codes, as they could offer up good trouble shooting clues.

Were the replaced IAC's dirty/oily/carboned up???? If so, suspect something like a mucked up PCV valve, or kinked, or cracked hose to it.

After a battery disconnect, that wipes the computers KAM, in which resides the cold & warm idle strategy, have you done the cold & warm idle relearn proceedure here???
Ford Truck Enthusiasts Forums - View Single Post - high idle problem

Nov 12, 2012 | 10:10 AM

Hank85713

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From: Tucson USA

I had a problem and after a couple of hours with all the tech manuals and computer scopes etc, it was determined that the wire had a short somewhere in the bundle that it is routed through. Never did figure it out so now just run it disconnected, I did run the idle nut out a little. Still hold 750 rpm with the ac on so its good. Have had it like this for almost 6 years no problems. Does not over rev with the ac off but hold around 8-900 rpm. Makes life easier without having to worry about the engine speeding up at stops.