Low Idle
Thread Starter
3rd Gear
Joined: Jan 2003
Posts: 3
Likes: 0
From: Rockton Pa
Low Idle
I just bought a 86 coupe and love the car BUT when you stop at a traffic light the idle drops to 400 or 500 RPM what is my best choice to fix this and how do you adjust the idle speed? THANX 86 and 74 VETTESTER
2nd Gear
Joined: Aug 2001
Posts: 2
Likes: 0
From: Burlington Vt.
Re: Low Idle (vettesterr)
I have an 89 and have the same problem. It is not a constant problem. Its seems to happen most when I have driven for a while and the car is hot. I done a complete tune up and replaced the Ecm. I spoke with the mechanic that worked on the car from when it was purchased untill about 4 years ago. he seems to think that adjusting the idle wont help because the idle speed is controled by computer. There are a couple more items that he sugested that I check, I will check the list I have at my office tomarrow and update you. Good luck. Can anyone else help???
Melting Slicks
Joined: Apr 2001
Posts: 2,114
Likes: 220
From: Ca.
Re: Low Idle (c4&after)
Idle problems-both high and low are most commonly caused by the iac. (idle air control valve) The ecm sends a command to the iac to increase or decrease counts (open or close more) to adjust the idle. If it's sticking either open or closed the ecm has no way of knowing that to set any kind of a code.
I'd first try removing the iac and really cleaning out the passage-use a rifle bore brush or similar to scrub out the passage in the throttle body. If the iac itself looks all gummed up just replace it.
If you can scan it and it shows iac counts of 160 (wide open) as the ecm tries to increase the idle then it's definitley the iac.
I'd first try removing the iac and really cleaning out the passage-use a rifle bore brush or similar to scrub out the passage in the throttle body. If the iac itself looks all gummed up just replace it.
If you can scan it and it shows iac counts of 160 (wide open) as the ecm tries to increase the idle then it's definitley the iac.
