Vette with strange idle problem
Thread Starter
Instructor
Joined: Apr 2008
Posts: 247
Likes: 1
From: Ohio
Vette with strange idle problem
Ive got an 86'coupe ive had for about month and since ive owned it ,it has a strange sequence it goes thru before it goes to (normal idle).I start the car (warm or cold) and at first it will rev up to about 1300 rpms for a moment then after about 2 or 3 minutes ,it will drop down and fluctuate between 1000 and 900 rpms then it will idle at 700 rpms.
Maybe a bad idle air control motor ??? any suggestions? Im all ears
Maybe a bad idle air control motor ??? any suggestions? Im all ears
Drifting
Joined: May 2002
Posts: 1,562
Likes: 1
From: "Drive like Hell, you'll get there faster." Tucson AZ
IAC is possible but it would usually just drop to the point near stall. Since its revving, have your throttle position sensor checked and/or try disconnecting it at the connector and making sure the little holes are free of any contaminants. The revving happened with my 90 to a point it almost seemed like a cylinder was misfiring, but it turned out to be a TPS gone haywire over time. I'd also clean out the throttle body with some top engine cleaner just in case there's any buildup.
Slingshot
Joined: Dec 2001
Posts: 3,817
Likes: 24
From: Charlotte NC
Remove your throttle body and clean it with a good carb cleaner. Remove and clean the prindle on the IAC and then reset the Throttle Position Sensor to factory specs. Also, put a bottle of STP fuel injector cleaner into your gas tank. These steps should solve your idle problems.
You can use the search function to look up the details for each step outlinned above.
You can use the search function to look up the details for each step outlinned above.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
It sounds to me like the IAC is working. That is what is varying the idle speed. If the IAC passages were plugged up, chances are they wouldn't pass enough air for a 1300 rpm idle speed. Check the connection to, and ohm check, the ECT sensor. If the ECM thinks the engine is cold it will call for a cold fast idle. Also check for intermittent vacuum leaks.
Interesting to see advice from someone that was seeking advice on a similar problem, just today. What is "Since its revving, have your throttle position sensor checked and/or try disconnecting it at the connector and making sure the little holes are free of any contaminants" on the TPS? What holes with contaminants? To what detrimental effect? Also, "revving happened with my 90 to a point it almost seemed like a cylinder was misfiring" makes no sense. You are advising "I'd also clean out the throttle body with some top engine cleaner just in case there's any buildup." when just a couple if hours ago YOU were asking what to clean your TB with and none of your answers were "with some top engine cleaner". It is nice that you want to help out, but wrong or inexperienced advice can be worse than no advice.
RACE ON!!!
Originally Posted by MaSTeRofDZaSTeR
IAC is possible but it would usually just drop to the point near stall. Since its revving, have your throttle position sensor checked and/or try disconnecting it at the connector and making sure the little holes are free of any contaminants. The revving happened with my 90 to a point it almost seemed like a cylinder was misfiring, but it turned out to be a TPS gone haywire over time. I'd also clean out the throttle body with some top engine cleaner just in case there's any buildup.
RACE ON!!!
Last edited by CFI-EFI; May 5, 2008 at 08:50 PM.
