Intermittent Idle Issue
Thread Starter
Instructor
Joined: Jul 2014
Posts: 151
Likes: 5
From: Jonesborough TN
Intermittent Idle Issue
Every once in a while when starting my 89 it doesn't want to idle. When it starts it doesn't start as well, like it wants to die. There is no pattern to it as it has happened after sitting in the parking lot overnight on a cool morning when I work night shift and today I stopped to get some food on the way to work and it did it when the car was warmed up. At red lights it would get down to 500 rpms if I didn't give it some gas. It runs fine when moving. What should I check first? CEL never comes on. I checked for codes a while back and had none. I did notice today that the avg mpg and the trip odometer reset after starting it when this occured.
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
There are a bunch on grounds that are either on the side of the block above the oil filter or on one of the bell housing bolts, depending on the year. Check for cleanliness and tightness.
Oil Producer
Joined: Apr 2014
Posts: 9,365
Likes: 2,734
for me those exact conditions was the iac in the throttlebody
i took tb off, cleaned, replaced gasket for 4$ and iac for 50$ and fixed. there are a couple youtube vids showing how to do it. maybe there is a way to narrow down things. i checked my fuel system pressure first before doing the iac.
Thread Starter
Instructor
Joined: Jul 2014
Posts: 151
Likes: 5
From: Jonesborough TN
Team Owner
Joined: Jul 2004
Posts: 28,422
Likes: 3,275
From: Hartford WI
I just tried the Actron ones and it didn't work. Called the company and they said they don't support it. I have an old Auto X-ray and it works for my 91 Vette. I would suggest you get one from them so it can cover other models and you can help others who might toss a few bucks your way to cover the investment.
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Safety Car
Joined: Nov 2008
Posts: 4,328
Likes: 15
From: Jacksonville FL
True scanners, not code readers, are worth every penny you invest. They can help narrow down a problem that hasnt set a code yet just by the info they supply. It will read IAC counts, TPS voltage, MAT/MAP readings, all things that will affect your idle. You need to have one when the car is havings its issues to scan what is going on. I have an Auto Xray 240 which I picked up off ebay for $60. Its only an OBD1 but it provides about 20 different readings important for diagnosis. Get an appropriate scanner and post up the readings.
Aklim has given you good advice, start with the basics and free things like grounds and other connections. Its good maintenance and if you luck out and it fixes you issue, you havent spent any money throwing parts at the car.
And as always, good luck!
Aklim has given you good advice, start with the basics and free things like grounds and other connections. Its good maintenance and if you luck out and it fixes you issue, you havent spent any money throwing parts at the car.
And as always, good luck!
Thread Starter
Instructor
Joined: Jul 2014
Posts: 151
Likes: 5
From: Jonesborough TN
I haven't had much time to work on the Vette with work and everything else, but, I sprayed some Sea Foam throttle body cleaner in the hole in the throttle body onto the IAC valve and let it sit for about 10 minutes then cranked her up. It's only been a couple of days and it seems to idle and run a lot better now. The previous owner installed the TPI intake air foil and to me it looks like it restricts airflow to the IAC valve. Does the air foil really make any difference in performance?