IAC valve question
Thread Starter
Burning Brakes
Joined: Mar 2012
Posts: 889
Likes: 24
From: Fort Worth Texas
IAC valve question
Is their any way to check a IAC valve to see if it bad? My 86 coupe idles real low when it's cold and stalls sometimes too, if you try to give it gas it back fires and pops from the throttle body? After it warms up it runs pretty good except for a slight miss, other wise it Runs great. I changed out the TPS and that didn't help, cleaned and rebuilt the throttle body that didn't help, new plug wires, plugs, distributer ,rotor ,new fuel injectors , any ideas?? Thanks for your help in advance.
Team Owner
Joined: Jan 2003
Posts: 20,297
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From: Summerland B.C. Canada
Le Mans Master
Joined: Feb 2005
Posts: 6,477
Likes: 565
From: Clearwater Florida
..... Check / set the timing and then set the minimum idle per the Factory Service Manual and then recheck the TPS voltage ... as WW7 mentioned , you can hook up a scanner and check the IAC counts ... they should start out high when the engine is cold and as it warms up they will slowly drop to the 30-ish range .............
Burning Brakes
Joined: Aug 2004
Posts: 1,174
Likes: 125
From: Dunstable MA
St. Jude Donor '05
Low Tech Quick Check: With the car at idle, gently rotate the TPS arm away from the throttle body arm that actuates it. This actuates the TPS without opening the throttle plates. If the IAC is working, the engine RPM will go up in response.
The problem you are having, however, sound like a vacuum leak or the EGR stuck open.
The problem you are having, however, sound like a vacuum leak or the EGR stuck open.
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Thread Starter
Burning Brakes
Joined: Mar 2012
Posts: 889
Likes: 24
From: Fort Worth Texas
Ok I followed the FSM ( thanks to you agent 86) 
on how to trace the issue and it seems to be either the IAC valve of the IAC valve connecter. So I'm going to order a new IAC valve and I believe that will solve the issue. Thank y'all for the help I appreciate it !!!
on how to trace the issue and it seems to be either the IAC valve of the IAC valve connecter. So I'm going to order a new IAC valve and I believe that will solve the issue. Thank y'all for the help I appreciate it !!!
