IAC woes...

bdeuce · Aug 7, 2007

i have a 1990 Bronco II, 2.9. recently, with someone at another site touting all the benefits of cleaning the IAC, and suggesting it was at the root of every driveability problem anyone had, i decided to clean mine. took it off, sprayed it with carb cleaner, replaced the o-ring, new gasket, runs like crap. idles (barely) at about 200 rpm. lots of power - grunt is there, top end is there; push in the clutch while shifting, rpm's drop like a stone and it'll almost stall. i checked all my vacuum lines, all seem to be okay. while running, i unplugged the IAC and nothing happened. could i damage it by cleaning it? going to pull it sometime and bench-test it; saw somewhere about applying voltage and observing the solenoid activity??

Nate

F150hybred · Aug 7, 2007

Nate, a quick test would be to increase the engine rpm manually to the specified idle. If it sounds proper, odds are, your IAC is crapped or you have a poor connection. Your engine will idle at an extreamly low RPM if it's not working. Reason being, there is a throttle stop screw that helps keep the throttle BARELY open at idle. DO NOT PLAY WITH THAT SCREW! Funny thing about those IAC things, it usually causes more harm than good when cleaned as opposed to simple replacement. Honestly, I have never played with my IAC and I have over 400k on the engine. Some things are better left alone. I hope that helps yah bud!

Wicked_Sludge · Aug 7, 2007

pull the IAC back off, plug it in and have someone turn the key to "run". the IAC should open temporarily, then close again.

sounds more like a vacuum leak to me.

for the record, ive cleaned the IAC on all 3 of my fords and 2 of them experienced a noticeably smoother idle afterwards.

Loanranger · Aug 8, 2007

Actually, I was just getting on to mention something about screwy idles, as 4x4Junkie and AllanD have helped me in the past with this. The first time, I had it Idle down slowly, then just die. It wouldn't happen all the time, just every once in a while. Well, that time, I had checked everything possible, including cleaning the IAC and replacing the MAP with a junkyard one. None of this helped, and after thinking about it, I decided to just check the timing. Well, needless to say, it was way off, by nearly 8 degrees, though I can't remember which way now, but this cured the problem and I haven't had it since. Then a couple weeks ago, I started out to work in the morning, and had to stop for construction about 5 minutes after leaving the house. Well, when I came to a stop, I noticed the idle hovering at 2 grand, it slowly worked it's way down, and I started thinking my distributor had slipped again, so when I got home, I hooked the timing light up, took out the "pill", and everything checked out. Strange. So the next thing I tryed was I took the IAC off, took off the solinoid, and soaked the main part in carb cleaner. I took a spray gun cleaner brush (basically a pipe cleaner) and started brushing around, getting all the soot out. I made sure I got as much as I could, and let it dry, even blowing it out with an air hose, just to make sure all of the carb cleaner had evaperated. I then reinstalled it, and haven't had a problem since. So it does work to clean it out, depending on your situation and it's condition, and it's well worth it compared to the price of a new IAC.

bdeuce · Aug 10, 2007

it's all good now. disassembled it again, put a drop of oil inside. works like a champ. weird.

thanks to everyone who advised...

nate

fireguy12117 · Aug 11, 2007

just thought id add that my 93 IAC woes were the result of a bad wire in the harness bundle as it leaves the weel well shroud and jumps over to the engine block. there is a red and a blue-white (or was it white/blue) wire on the IAC harness. the blue/white wire was completely open. this wire connects directly to the PCM. ran a new wire with water tight splices and havent had a problem since. i had nearly all the same symptoms that everyone has described here.

IAC woes...

bdeuce

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F150hybred

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Wicked_Sludge

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Loanranger

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bdeuce

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