Idle Surge; only when warming up

[TSIkw]

I am getting the typical 500 RPM range idle surge going between 1000 and 1500. This does not happen when i first start the car. It begins once the car starts warming up and stops once its at running temp. It was doing it all the time and i found that the o ring on the biff screw was leaking and it kept backing out, so i fixed that. I can't find other vacuum leaks and don't think there is any since it stops surging once its warmed up all the way.

Any ideas of why it only surges when the car is "adjusting" the idle as it warms up.

 

[95blackGsTurbo]

Check your ISC. Common problem on DSM's. Search this problem and you will find hundreds of threads about it and what it is and does. Idle Speed Control motor.

 

[92eclipse_gs]

I have the same exact problem and i figured out that it was my ISC. I'll give you some steps on how to check it.

First make sure your car is nice and cool. Then unplug the electrical connector from the ISC motor and there will be 6 pins. get your ohmmeter and measure ther resistance between pins 1-2, 3-4 and so on. you should get between 28 to 33 ohms between each of the pins. If you get some sort of erratic reading then most likely your ISC is bad. Which it is in my case. I found a site that rebuilds them and sells them for 89 instead of the typical 180. The site is

http://www.crebotech.com/

You could also try cleaning your throttle body with some carb cleaner, that might make it a little better.

But do that test and let me know.


-Nick

 

[BaddAssGst]

I would say it's a bad FIAV (fast idle air valve). I had this problem with 2 throttle bodies. It takes a second for the coolant to make it to the throttle body which is the delay and then after a minute, it will start to surge back and forth. One the car is warmed up, the FIAV is basically no longer used, which is the reason it stops surging.

It's part of the lower half of the throttle body. You can block it off (not recommended) or find someone who has a spare lower half or complete throttle body and swap with them. It took me 2 throttle bodies to find one that didn't surge.

 

[TSIkw]

Thanks for the help guys! I'll check out both possibilities.

 

[95blackGsTurbo]

I would say it's a bad FIAV (fast idle air valve). I had this problem with 2 throttle bodies. It takes a second for the coolant to make it to the throttle body which is the delay and then after a minute, it will start to surge back and forth. One the car is warmed up, the FIAV is basically no longer used, which is the reason it stops surging.

It's part of the lower half of the throttle body. You can block it off (not recommended) or find someone who has a spare lower half or complete throttle body and swap with them. It took me 2 throttle bodies to find one that didn't surge.

I would check this first. I misread your post. If it stops once the car is warm this is a good place to check first.