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2002 STS, 2005 CTS 3.6
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Discussion Starter #1 (Edited)
Re: P0507 code on 98-04 Northstars

After cleaning my throttle body and messing around with two junkyard IAC motors, because of having crazy (rolling up and down & stalling) idle control issues on my 2002 SLS...I stumbled upon something that seemed to be the cure and I've never seen it mentioned on this site. Ends up, the IAC being dirty isn't the biggest issue, but the PINTLE VALVE that comes LOOSE!

While sitting at my bench in the garage, contemplating how I got two bad IACs in a row, I got ticked off and wanted to figure out how these things work and happened to twist hard with my fingers on the end of the pintle valve and it came loose. Light bulb went on in my head, and I began to turn it all the way out of the body until it was in three pieces, the pintle, a spring that is inside the steel collar and the IAC body.

The plunger is on a threaded rod and over time, vibrations must cause it to loosen and turn itself out, seizes up with crud, and then the IAC motor can no longer pull the pintle back far enough from the throttle body idle port for proper idle. Either that or the motor just gets plugged with gunk or weakens and the re-adjustment allows it to be put back to spec. I even thought about putting a dab of Loctite on the threads before screwing it back in, maybe next time.

After cleaning the whole works with throttle body cleaner, I reassembled it all and turned it all the way back in to the body until it was seated, finger tight and reinstalled the unit back into the throttle body. After a short re-learn, drive time and a couple of starts...presto! The engine starts up and runs exactly as it should, goes to about 1200 when cold, down to 900 and eventually settles at 650 RPM. No more stalling or hunting up and down idle...three months later, the engine still idles and runs great. Also this was on my original IAC, and it often wouldn't start and barely ran with this one, before and after cleaning.

Note: I did not use any actual relearn procedure, I basically just let the PCM do its own thing. Although there is a procedure from the FSM, provided by Sub409 :

Key: ON, Key: OFF, Start the engine and let the fast idle sequence - 1200 rpm, 900 rpm, 650 idle - complete. Turn the engine off for at least 15 seconds. Restart and check idle speed at about 650.

So, do not bother buying an expensive new IAC valve! Try this first, just clean everything up good, tighten the pintle back in and re install. Idle should come back to normal within a couple of key cylcles and some run time. Good luck!
 

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2002 STS, 2005 CTS 3.6
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413 Posts
Discussion Starter #3 (Edited)
Great, should help out a lot of people. I wish I could provide pictures, but I barely know how to type. Lol!

Furthermore, I'm betting there is some sort of spec for measuring the length that the pintle should be from the body or the steel collar that surrounds the shaft. Perhaps something in the FSM? The plunger almost bottoms out on the collar when you screw it all the way back in. This is likely where it should be for an initial cold start up for high idle.

Also, I'm not sure as to what the exact re-learn procedure is. I just fired it up for about 15 seconds, shut it off for another 15 and started it again and drove around for a bit and the idle settled on its own.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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The GM IAC relearn - not Idle Speed Control for earlier models - Idle Air Control - is Key: ON, Key: OFF, Start the engine and let the fast idle sequence - 1200 rpm, 900 rpm, 650 idle - complete. Turn the engine off for at least 15 seconds. Restart and check idle speed at about 650. Good to go.

EDIT: here's a link to a CF thread on the same IAC problems - with pictures.

http://www.cadillacforums.com/forums/cadillac-deville-1985-2005-including-1985/672817-p0507-code-2001-deville-base.html#post14012553
 
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