Bad Iac Valve Again?
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Pro
Joined: Oct 2001
Posts: 554
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From: CA
Bad Iac Valve Again?
Maybe I should take a different approach....what causes the IAC valve to go bad? The one replaced by the dealership maybe lasted 18 months. The next one from autozone lasted about a year. And now my current one from autozone has appeared to have gone bad after eight months. Just bad luck with these parts or is something causing the part to fail? Symptom: rough idle, surging idle, near stall at idle. The part swap has cured the problem every time so I am 99.9% sure the the problem was the part. I did the TB cleaning by the way. 
DAMN 3 month parts warranty!!
DAMN 3 month parts warranty!!
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Originally Posted by gpagaduan
Maybe I should take a different approach....what causes the IAC valve to go bad? The one replaced by the dealership maybe lasted 18 months. The next one from autozone lasted about a year. And now my current one from autozone has appeared to have gone bad after eight months. Just bad luck with these parts or is something causing the part to fail? Symptom: rough idle, surging idle, near stall at idle. The part swap has cured the problem every time so I am 99.9% sure the the problem was the part. I did the TB cleaning by the way. DAMN 3 month parts warranty!!
DAMN 3 month parts warranty!!
I had my IAC " go bad" twice in last two years. Let me define bad as OUT OF ADJUSTMENT!On both occassions, the Needle valve was too far out (1 1/8") ids factory adjustment and mine was like 1 1/4"
I was getting low MAF codes and before the codes and engine would cut off momentarily.
I am not sure why it happens other than I think the ECM sends wild counts to the IAC in order to try to control idle. I also suspect that carbon build up in the IAC keeps it from responding to all the ECM commands so the Ecm keeps sending them.
I adjusted mine twice, with mixed results and finally replaced it with an ECHLIN unit from Napa. Actually running improved over the hole range of RPM.
Do you have a scanner to read the various sensors and voltages? This is a worthwhile ($200) investment. I had a MAF relay going bad and that might have caused some IAC problems
Race Director
Joined: Sep 2000
Posts: 17,298
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From: The Top of Utah
Originally Posted by jackdaroofer
I had my IAC " go bad" twice in last two years. Let me define bad as OUT OF ADJUSTMENT!On both occassions, the Needle valve was too far out (1 1/8") ids factory adjustment and mine was like 1 1/4"
RACE ON!!!
Heel & Toe
Joined: Aug 2003
Posts: 17
Likes: 0
From: memphis tn
I've replaced my IAC three times in 6000 miles. Each time the new IAC [a c delco] solved the problem for a few months.The last time it went kapoot on a road trip in the mountians 'not much fun' because it would not idle I traced down the root of my problem. Bad EMC. Have not had any IAC problems since.GOOD LUCK
Burning Brakes
Joined: Apr 2004
Posts: 762
Likes: 2
From: Huntington ma
Most likely the "bad IAC" is really a clogged (with carbon) up throttle body, Or worn out bushings in the shaft that carries the throttle butterflies. When the bushings wear (or the bores get all crudded up)the butterflies won't close "cleanly" - that makes life hard for the IAC as the ECM has to constantly fiddle with it to try and hold the desired idle speed. If the butterflies close like they should then the IAC really doesn't have much to do - it'll last nearly forever! BTW - keeping a "fresh" PCV valve on the motor does wonders to reduce the amount of crud buildup on the throttle body.... That and replacing worn out pistons/rings to stop all the blow-by in the first place 
Team Owner
Joined: Sep 2002
Posts: 22,209
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From: OBAMA IS HITLER
Originally Posted by FOR PLA
I've replaced my IAC three times in 6000 miles. Each time the new IAC [a c delco] solved the problem for a few months.The last time it went kapoot on a road trip in the mountians 'not much fun' because it would not idle I traced down the root of my problem. Bad EMC. Have not had any IAC problems since.GOOD LUCK
Last edited by Red Tornado; Aug 5, 2004 at 07:37 AM.
Drifting
Joined: Nov 2002
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From: Mobile AL
St. Jude Donor '05
Good advice, all. Clean all the carbon out, especially around the seat of the IAC. Also make sure you do not leave the old "O" ring in there, and put the new "O" ring in to make sure it's seating before installing the IAC.
