I want to clean my Idle Air Control (IAC) valve. I read on the forum that I need to use a sensor-safe carb cleaner. What is this, and how important is it?

For that matter, how should I go about cleaning it?
My engine's bucking cold under load, and my strongest guesses are a bad IAC, faulty Thermac, faulty MAP or faulty TPS. It's a '84 Duke manual. It ran find in warm weather, which is why Thermac is my strongest suspect.

-Michael

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"A guy know's he's in love when he loses interest in his car for a few days." -Tim Allen

He who dies with the most toys... still dies.


My '84 Resto

Sensor safe is talking about the O2 sensor. This would be important if you were spraying throttle body cleaner into the throttle body itself since the fluid would get burned and make it's way to your O2 sensor. However, cleaning the IAC is done with the IAC removed from the throttle body so it really does not matter what you use. Some carb cleaner and an old toothbrush works just fine. Or a small bucket of gasoline, mineral spirits, (whatever you have) and a brush will clean it. You are just removing the oily gunk that builds on the spring behind the pintle.

Yes in IAC passage in TB/TBI unit.

No in IAC unit itself. use electrical cleaner. get at radio shack etc....

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave (It's also at the top and bottom of every forum page...)

Yes, you could just spray the cleaner down the IAC passage. That would cause the gunk to be flushed into the engine though. I would suggest if you have the tools and time to remove the IAC and clean it off the throttle body.

These seem like different responses.

Ogre- I don't understand what you mean, and I didn't find the answer in your cave. Do you mean that using carb cleaner on a removed IAC valve is bad for it and that I should use an electrical cleaner? I'm not quite sure what an electrical cleaner is. Do you mean that mineral spirits harm the IAC component?

I will be removing the valve, as I don't what that junk in my very clean engine.

-Michael

I use brake clean with the engine running air intake hose off, rev the engine up to about 3-4K and start dousing the IAC passage for about 30 seconds and adjusting the throttle to keep it running, then let the throttle snap close and bring the engine down to idle. Open the throttle to bring it back to 3-4K and repeat about 4 or 5 times.

With the engine stopped, open the throttle blade, spray around the bore and take a rag to wipe away all the carbon build up on the back side. Too much buildup on the back side makes the throttle blade seal too well and requires the IAC to accomodate all idle air vs. just the additional amount over and above what leaks around the throttle blade.

most cold running issues are the 2 temp sensors
the MAT & CTS. the MAT is on the air filter can & the CTS is on the intake manifold, at the very front - sticking out towards the pulleys.

anyways - for the cleaner. what you want is called "Throttle Body Cleaner". it is basicly the same as Carb Cleaner, except, sensor safe. and shoot it down the IAC hole in small spurts.

The valve... use electrical cleaner. get at radio shack etc....
See http://www.radioshack.com/p...sp?productId=2102649

Throttle Body Cleaner is good for TB/TBI units. Besides sensor safe, (Sensor Safe means more than O2 sensor... Carb cleaner hate MAT in 87-88 L4) safe for many Al part with some finish (Like paint) that carb cleaner can eat finish.

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave (It's also at the top and bottom of every forum page...)

Thanks Ogre, Pyrthian, Guru & Hudini,

I cleaned up my IAC valve, started it up, and my idle went from 3k (previously idle) to 600. I didn't expect such a big difference. Is 600 a bit low? I still have to check my coolant temp sensor. Could a map sensor also be an issue? And, am I right that the fan switch and the temp gauge sender don't affect the ecm at all?

Michael

yes, the fan switch & the temp guage sender do not go thru the ECM at all.
3000 to 600 is quite a drop. almost sounds like the IAC went from being stuck open to stuck closed. yes, 600 is a bit low.

,, Driving the car may cause the EMC to ajust the idle ,drive at 35 to 37 mph for a short distance
..I would check the timing
..painting a white mark on the timing slot makes timing easier
.. your tach may not be accurate at lower speeds ,, you can tell by the idle speed i fit seems proper,,your car should idle at 800 rpm or higher ,,My car idles at 1100/1150 RPM ,but it sounds correct

I used throttle body cleaner on an old IAC that wasn't working very well - and killed it completely.

quote Originally posted by 85 SE VIN 9: I used throttle body cleaner on an old IAC that wasn't working very well - and killed it completely.

Oh. How do I know if mine's dead? I got the ogre's second message on electrical cleaner after I'd already used sensor safe throttle body cleaner. I figure that since it said "sensor safe" that perhaps it was the same thing as electrical cleaner, or at least was safe for my iac.

As my idle speed is about the same cold as hot, if anything higher when hot, it looks like I may have killed my iac. Gosh,... as they say, haste makes waste.

That may now be the source of all my problems. I put on my thermac tube yesterday. That helped a lot. She still likes to buck a bit when cold, if I'm not careful with the clutch and throttle. Is it likely that this, too, is the iac? I'm also running rich, even warm, so I figure that might be the map.

-Michael

-Michael

To find out if it's dead just reset the IAC. First jumper pins A&B on the ALDL connector. Then turn your key to ON. Now walk back and put your hand on the IAC. You should feel and hear it clicking rapidly. What it's doing is being commanded fully closed. If it's not clicking rapidly = dead. If it IS clicking then simply pull the electrical connector from the IAC. This freezes the IAC fully closed. Now walk forward and turn the key OFF, then remove the jumper from the ALDL connector. Now walk back and reconnect the IAC electrical connector. You have just reset the IAC to a known position for the ECM. Now drive the car over 35 mph to relearn idle. The car should idle fine as it is but get more accurate the more times you drive it over 35 mph.

Here is jetman's dirty console showing the ALDL port.


EDIT: BTW, when I rebuilt my 700 series throttle body (87 Duke) I cleaned the IAC in a bucket of mineral spirits with a toothbrush. It worked fine. If your IAC is dead then it was already dead before you cleaned it IMHO.

[This message has been edited by Hudini (edited 01-05-2011).]

Thanks, I'm about to go try that. I just tried something else that was suggested: I pulled the plug on my map sensor to see if I found any change. I drove about a 1 mile stretch w/ and w/o it and didn't really notice any difference. It may have even been better w/o it. In like manner I tried the same with the iac valve. I this time only drove up the street and back, but I noticed no difference at all. When I unplugged the map, the check engine light came on. However, when I unplugged the iac, the check engine light didn't come on. Idle seems to have evened out to about 900 when warm, but it's still not higher when cold.

I'm gonna go do the iac reset thing at the aldl, and I'll report when I return, probably in about an hour or so.

-Michael