Air intake valve problems
New User
Joined: Jan 2002
Posts: 16
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From: North Pole USA
Air intake valve problems
O.K. I was dinking around with my truck (91 Ford F150) and trying to get the high idle solved. Sprayed the beejeesus outta the aic valve, and the relay, too. Now it idles at 1800 instead of the 1500 that it's been doing. What now? I have not tried the voltage check as it seems thart it's gonna be off anyhow. Tried the unplug option, and there was no change. It's driving me crazy in a hurry.
Senior User
Joined: Jan 2001
Posts: 416
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Air intake valve problems
Sounds like the IAC may be stuck in the open position as unplugging it will cause it to run so rough that it will stall. Take the IAC off and clean it again. Try to blow through the bottom hole. There shouldn't be any air bypassing. Perhaps a bit of crud got stuck in the valve.
New User
Joined: Jan 2002
Posts: 16
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From: North Pole USA
Air intake valve problems
Thanx, I'll give it another shot. It's so crazy, it's JUST a chunk of metal and should not be too hard to figure out. Just how does the attached relay thing work, anyway? My next step is to buy another one, but with markup being the way it is in AK, it'll probably cost an arm and a leg, and I need those.
Elder User
Joined: Apr 2001
Posts: 772
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From: Glen Burnie Maryland
Air intake valve problems
>Thanx, I'll give it another shot. It's so crazy, it's JUST
>a chunk of metal and should not be too hard to figure out.
>Just how does the attached relay thing work, anyway? My
>next step is to buy another one, but with markup being the
>way it is in AK, it'll probably cost an arm and a leg, and I
>need those.
the IAC is a one way valve that is operated by the "RELAY" which is actually a computer controlled stepper solenoid. With VOLTAGE OFF the solenoid is retracted and the valve is closed, or stepper is energized and valve is extended. Variable voltage is applied to IAC by computer to regulate idle speed.
If the valve (ceramic ball and seat) becomes contaminated it will not close and will admit excess air causing high idle.
Pull the unit off the Intake manifold and turn it upside down. Using carb cleaner and a VERY SMALL PARTS BRUSH clean the exterior surfaces 1st and then soak the inside (2 holes) for about an hour. Flush out the valve (both sides) and work the brush inside to loosen up any residual contaminants. Flush again. You should be able to move the ball slightly to check for cleanliness. Once you're satisfied it's clean, re-install. Start engine.
If you're REALLY CAREFUL you can remove the solenoid from the IAC for more thorough cleaning.
Larry
>a chunk of metal and should not be too hard to figure out.
>Just how does the attached relay thing work, anyway? My
>next step is to buy another one, but with markup being the
>way it is in AK, it'll probably cost an arm and a leg, and I
>need those.
the IAC is a one way valve that is operated by the "RELAY" which is actually a computer controlled stepper solenoid. With VOLTAGE OFF the solenoid is retracted and the valve is closed, or stepper is energized and valve is extended. Variable voltage is applied to IAC by computer to regulate idle speed.
If the valve (ceramic ball and seat) becomes contaminated it will not close and will admit excess air causing high idle.
Pull the unit off the Intake manifold and turn it upside down. Using carb cleaner and a VERY SMALL PARTS BRUSH clean the exterior surfaces 1st and then soak the inside (2 holes) for about an hour. Flush out the valve (both sides) and work the brush inside to loosen up any residual contaminants. Flush again. You should be able to move the ball slightly to check for cleanliness. Once you're satisfied it's clean, re-install. Start engine.
If you're REALLY CAREFUL you can remove the solenoid from the IAC for more thorough cleaning.
Larry
New User
Joined: Jan 2002
Posts: 16
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From: North Pole USA
Air intake valve problems
Okay, I have pulled the solenoid, not too tough, just a couple screws and don't drop the o-ring. It's cleaned. I have thouroughly doused the valve assembly and it is clean. When I reinstalled the relay I noticed that it pushes the valve open slightly. This is with the relay diconnected electrically. When apart, I can't blow air through the bottom hole of the valve, but if I connect it, then it opens enough to allow air to pass though. I may bite the bullet and just get a new one. If it does the same thing, then I take it back. If I don't and fix the problem, then I'm bucks ahead anyhow.
Senior User
Joined: Jan 2002
Posts: 185
Likes: 0
From: Central Florida, USA
Air intake valve problems
My '92 5.0l with 156K on it had a the same problem. It was caused by a pretty big air leak, actually a couple of them. I found the first one to be the intake manifold gasket. That was the low cost fix and it only took a couple of hours. I worked around the real fix for a long time because I did not think the throttle body could be causing the problem. I had it off, cleaned it and put it back on several times before finding out that due to wear and age the body itself was leaking air and causing the high idle. I had to order the part from Ford so it wasn't a 'low-cost' fix, but fixed it is. I reset the computer so it could re-learn with the new mixture settings and Bob's your uncle, 700 rpm idle again. Better MPG too. Hope this helps.
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Senior User
Joined: Jan 2001
Posts: 416
Likes: 0
Air intake valve problems
Sounds like you are having the same kind of problem I am having except mine does the opposite, it tries to stall at stopsigns. I have cleaned mine a number of times and is behaving right now but for how long? I noticed that my IAC did the same thing as yours, was sealed until I attached the solinoid then it is just a tiny bit open. I figure this valve should be completely closed when the power is off. Does anyone have an opinion on this? I am not sure if the valve is worn or if the solinoid is faulty therefore holding it open. None of the manuals I have read say anything about this.
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Elder User
Joined: Oct 2001
Posts: 750
Likes: 2
From: Buena Vista
Air intake valve problems
You just disconnect your battery, and also pull the headlight switch all the way out, to drain the capacitors. I think all it takes it like 20 mins. To 30 but you could just do it over night.
That should do it.
That should do it.
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