2G High idle

[kcd]

Hey guys.

So I'm having a high idle issue. From a cold start, it idles fine. Right about 1k rpms. Then once I start driving and then come to a stop, it idles at about 2k. If it's a long stop, it'll eventually find it's way back down to 1k.

I just replaced my IAC valve today because I thought that was my problem. But apparently not.

I'm guessing most of you will say it's a vacuum leak, but for the life of me, I can't find one. So frustrating.

Any ideas?

 

[Tiki2777]

If it's not a vac leak, then you may need to readjust your BISS (base idle set screw) AND reset your IAC. Reseting your IAC is an important part of getting your car to idle properly or your stepper motor will be out of range and not able to operate correctly. Also, your FIAV may be playing into this issue, but I doubt it unless you are experiencing an idle surge as well.

 

[kcd]

How do I reset the IAC?

 

[Type1DSMr]

How do I reset the IAC?

Disconnect the battery and let the ecu reset itself. When adjusting the biss screw, you need to ground it. Do you have ecmlink? If do check ground pin and ground timing when adjusting the isc.
The link is Terry trouble shooting for idle problems.
http://www.dsm.org/how-tos/tttt/tttt3.html

 

[kcd]

Unfortunately, I don't have link yet. I was reading up on it and you need some kind of scanner tool? I have one, but I doubt it's the right one.

 

[Type1DSMr]

Yes you need a scanner to get the isc position to around 30. The biss screw adjustments takes a while for the isc and ecu to settle in around 5 minutes per adjustment. Some people have said the base position for the biss screw is 2 full turns out from being tight, might get you by but my biss around 1 plus with ecmlink. So that's not recommended but may help til you can get it adjusted correctly. Also make sure the car is fully warmed up 186 or greater.

 

[kcd]

Can a shop adjust it for me?

 

[BostonGST]

you don't really need to ground anything. Just turn the screw and see how the idle changes. But it sound's like a vacuum leak, you did a boost leak test?

 

[steve]

Before playing with the BISS make sure your throttle cable isn't too tight. There should be a millimeter or two of slack in the cable before it starts to move the throttle. Check it when warm and you're having the high idle. Then once you're sure it's not the cable and you still have the problem you can adjust the BISS. A stock ECU will try to use the ISC to idle at 750rpm +- 50 rpm. If your idle is higher than that the ISC has been driven out of range and can't lower the speed anymore.

Did you check the old ISC to make sure it didn't have any shorted coils. If one or more of them drop much below the standard resistance damage to the ECU drivers can result requiring repairs.