IAC Ajustment PLEASE HELP !!!!!!!
Thread Starter
Heel & Toe
Joined: Feb 2008
Posts: 20
Likes: 0
IAC Ajustment PLEASE HELP !!!!!!!
I have a 1988 Corvette with the L98 engine. What is the ajustment specs on the IAC. How can you tell if it's working right. After running my car for a while and getting it hot, I went to a parts store. I left the parking lot and was approaching a stop light, when it idled down it was fixing to die so i had to keep my foot on the gas. After leaving the light i started getting on it , it seemed like it would surge sometimes. Everytime i would slow down and let my foot off the pedal it would want to die. If i let it sit for a few hours and restart it, it will run fine. This is driving me crazy. Could this be that i have a bad IAC or it needs to be ajusted. Its brand new from O'reilly's , it's been on the engine for a few months. Your help would be appreciated. Craig.
Pro
Joined: Jun 2001
Posts: 509
Likes: 5
From: Edmonds WA
I don't believe IAC motors or valves can be adjusted. But, they can stick, which can cause the kind of problems you are mentioning (dying at idle or failing to start without applying some throttle to allow air into the intake).
It's tough to tell if it's working right. It doesn't throw a code if it's stuck. If the IAC valve is stuck closed, there's no way for enough air to get into the engine at idle and it dies.
It could be a bad IAC, but the first thing to consider is if the throttle body was cleaned when the IAC was replaced? I found a lot of carbon built up in the throttle body where the IAC seats and cleaned it out thoroughly when I replaced my IAC.
And yes, this kind of intermittent problem drives you crazy! It drove me nuts for months and months (one wonders if I ever fully recovered ;-)
It's tough to tell if it's working right. It doesn't throw a code if it's stuck. If the IAC valve is stuck closed, there's no way for enough air to get into the engine at idle and it dies.
It could be a bad IAC, but the first thing to consider is if the throttle body was cleaned when the IAC was replaced? I found a lot of carbon built up in the throttle body where the IAC seats and cleaned it out thoroughly when I replaced my IAC.
And yes, this kind of intermittent problem drives you crazy! It drove me nuts for months and months (one wonders if I ever fully recovered ;-)
Team Owner
Joined: Sep 2003
Posts: 20,172
Likes: 672
From: Freedom is never more than one generation away from extinction.
St. Jude '03 thru '24
A simple check for operation is to remove the valve, connect it to the harness and turn on the ignition switch. (no start the motor) The pintel should unscrew itself and pop off the valve body. For this reason, place the valve in a plastic bag so you don't have to hunt for the flying parts....
Safety Car
Joined: Jan 2008
Posts: 3,939
Likes: 1
From: Vero Beach Florida
The distance from the tip of the pintle to the mounting surface of the IAC should not be greater then 28mm or 1 & 1/8 inch. The IAC adjustment automatically occurs after it’s on the motor, and is re-set after the motor has been started and shut off. I believe some scanning software will allow you to reset the IAC counts through the ECM. Take it apart and clean it measure it and see if that helps.
Instructor
Joined: Aug 2008
Posts: 132
Likes: 3
From: Springfield Ohio
keep in mind that this is the "Idle" air control. If the surge you described after "getting on it" continues while you have your foot on the gas (i.e. off idle) then the IAC would be eliminated from that particular issue. The other symptoms you describe could well be the IAC.
Good Luck!
Good Luck!
Thread Starter
Heel & Toe
Joined: Feb 2008
Posts: 20
Likes: 0
Thanks everyone for your help
I pulled the IAC out today and found that there was a piece of thread sealer that was on the thread of the IAC that was on the Pintle end. I cleaned it off, and it idles like a champ. Thanks again.
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Le Mans Master
Joined: Aug 2000
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From: Australia
Advanced
Joined: Mar 2001
Posts: 53
Likes: 2
From: Nashville, TN
I have a 1988 35th that has a similar problem. Mine will run and idle fine but sometimes when I start it, it want idle unless I keep my foot on the gas. Just tonight, it would not idle and died 4 times. The last time I turned the key off/on, restarted the car and it idled fine. Is it correct that once the car is turned off, the IAC will readjust? If that is the case does it not readjust once it dies and you restart it or only when it has been turned off? I will take it apart and clean along with replacing the fuel filter. Does anyone have pictures of this precess?
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
Stalling at idle is a prime symptom of needing to do a minimum idle adjustment, which consists of adjusting the throttle plates and TPS sensor. Instructions are here:
https://www.corvetteforum.com/techti...D=55&TopicID=2
https://www.corvetteforum.com/techti...D=55&TopicID=2
