: Idle Air Control Valve (IAC)

03-31-09, 09:26 PM
I need to replace the IAC valve on my northstar. I know that you cannot put one in and the engine idle fine. There is a procedure to "adapt" or "teach" it. Does anyone have this procedure?

03-31-09, 10:26 PM
I think it is just plug n play.

04-01-09, 10:09 AM
No unfortunately it's not plug/play. I have already tried this and when I started the eninge, it idled very high at about 3300 rpm. I am pretty sure there is a procedure to set the pindle at the right spot before installing it into throttle body. Otherwise the engine has no idle control. I was discussing this with the service advisor at the caddy dealership and he said there was a certain procedure (but of course they want me to pay them for the part/install and all that). So I am on here looking for some help.

04-01-09, 03:51 PM
IAC Valve Learn Procedure
Per '03 FSM

1, Start and idle engine for 15 seconds
2. Turn ignition switch to LOCK/OFF position
3. Wait 15 seconds.
4. Restart engine and check for proper idle operation.

04-06-09, 05:05 PM
I need to replace the Idle Air Control valve on my 03 Seville w/ northstar, but it is not a plug n play thing. From my understanding, there is a certain procedure or action that has to be taken before installing the new IAC valve, or else there is no idle control and the engine idles at 3000+ rpms. For example, the pindle on the valve has to be set to a certain distance...Does anyone know what I am talking about? Any help would be appreciated.

04-06-09, 08:24 PM
That is for the ISC (Idle Speed Control) motor on the pre '97's The IAC valve is plug & play. There is a simple idle learn procedure that I just posted a few days ago, but can't remember what it is. Do a search for it and if you can't find it, I'll look it up and repost it.

04-07-09, 06:57 PM
I don't mean to argue, but I'm not convinced it is a plug and play deal. I have already tried installing a new IAC valve and when I started the car, the idle was instantly at 3000 rpm and would not come down any. I had to shut the car off because the idle kept climbing. Is it possible I got a bad part maybe? Please advise

04-07-09, 10:47 PM
Well I just went back and found the idle learn procedure, but it was in an answer to you. Why did you start another thread? That just makes things confusing. I'll merge them.

04-08-09, 02:05 PM
Thank you Ranger... I never received an answer from anyone though. I started a new thread under a different forum because I thought maybe my thread wasn't being seen by the right people. Wasn't trying to be confusing... I'm a little new to this forum thing. I will try this procedure and see what happens. Should I do this when the engine is at operating temp? I ask this because if the car is cold, when first started it goes into high idle mode for about 30 seconds. I would think if did this during high idle, it wouldn't work out properly.

04-08-09, 04:46 PM
It makes no mention of operating temperature. I'd try it at normal operating temperature.

04-10-09, 03:29 PM
Just as I suspected... a class 2 scan tool is needed to accomplish the relearn procedure. It is not a do it yourself procedure.

12-10-09, 07:27 AM
I spoke with the head mechanic at the Cadillac dealership that I purchased my '02 Deville and he said to just start the engine after replacing the IAC valve, put it in reverse while holding the brake (foot brake, not emergency brake) and sit there for 10 minutes in reverse holding the brake. He explained that the engine will relearn the idle during this time. When asked about the ignition on ignition off procedure, he said that it does not always work and said the folks there use the reverse while holding the brake procedure. I have not tried either procedure yet but I plan on trying the "reverse" procedure once I replace my IAC valve, which should be here in a couple days.

12-10-09, 06:28 PM
I just replaced the IAC on my wife's 01 Deville, no issues with having to relearn. I believe when you turn the key off it drives full out and then retracts, thereby recalibrating itself.

01-05-10, 03:03 AM
I realize that they're completely different beasts STS, but I just had a similar experience with a 3.8 liter Ford V6 that I was working on.
It wasn't a defective new unit in my case, but instead was the wrong one completely. Even though it looked almost identical to the original, it was the wrong unit for this engine and it immediately went to 3000 rpm and stayed there. Sounds hauntingly familiar, as the song says.
The new unit bolted right on and had the correct connector. And it was specified in the computer, so I figured it must be right. Right? Not!

When it didn't function as expected, I went back armed with the original Ford part number (which I probably should have done in the first place) and, after cross-referencing it, realized that the wrong part number was loaded in the computer.
The right one settled right down to a normal idle with no fancy procedure and it worked just peachy after that. Plug-n-play, for the Mustang anyway.

I realize that this is no guarantee that a Cadillac will use the same (lack of) procedure, but wanted to mention it anyway.
I'll be interested to hear what you end up having to go through to make yours work. I don't suppose there is an easy way to test one of these things off the vehicle? It'd at least be nice to know you're not beating a dead horse, so to speak.


Locomotive Breath
02-25-11, 06:42 PM
IAC Valve Learn Procedure
Per '03 FSM

1, Start and idle engine for 15 seconds
2. Turn ignition switch to LOCK/OFF position
3. Wait 15 seconds.
4. Restart engine and check for proper idle operation.

I know this is an old thread, but I searched because I just bought a new IAC Valve.
I remembered reading the put it in reverse for 10 minutes thing, didn't work. I then looked at my manual and what Ranger posted is what the manual says. guess what, it worked.
No need for a scan tool at all.

02-25-11, 07:25 PM
I replaced my IAC valve on my 2000 Deville about 2 months ago.. Take the old one out and put the new one in... thats it...

Locomotive Breath
02-25-11, 07:53 PM
I replaced my IAC valve on my 2000 Deville about 2 months ago.. Take the old one out and put the new one in... thats it...I pulled my old one out, and it's plunger was fully compressed. The new one was extended. I did the swap and my idle went to 1500.
I tried the in reverse for 10 minutes and it fluctuated from 1275 and 1350 RPMs.
I did what Ranger and the manual said and it worked like a champ, restarted and it went to 650 smooth RPMs.

Obviously some need the relearn, and some do not.

04-22-12, 09:59 PM
Im having the same problem with my 1996 cadillac eldorado. I replaced the old IAC Valve, with a new one.. & when I turn on my car, it accelerates, and does not come down. Please give me step by steps please. God bless!

06-28-14, 09:54 PM

1/ Unplug the electrical connector on the valve by lifting the locking tab while pulling the connector out of the valve. Remove the 8mm bolts that attach the valve to the throttle body. Pull the valve off the side of the throttle body.
2/ Bolt the new valve and new gasket onto the side of the throttle body. Tighten the bolts securely. Plug the electrical connector into the valve.
3/ Start the engine and turn it off. Unplug the electrical connector from the valve. Start the engine and adjust the idle speed screw on the throttle body, using a screwdriver, until the engine idles at 675 rpm.
4/ Start the engine and adjust the idle speed screw until the engine idles at 650 rpms. This sets the base idle speed to a place where the valve can have full control. Turn off the engine. Plug the electrical connector back into the idle control valve. Start the engine. Verify the control of the idle speed by turning on the air conditioning and observing the change in idle speed when the compressor comes on.

06-29-14, 09:45 AM
He hasn't logged in for over 2 years.

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