Low Idle

[xGrafitti]

As the title says my 2g GST is idling at around 400-500.. Any suggestions to what it may be?

 

[miguelmcv]

Adjust the Biss to see if it brings the idle up.

 

[MiroDSM]

You need to check for boost leaks. Adjusting the screw won't do much, since you need to follow specific steps to make it work right

 

[NHerron]

Uh no don't touch the BISS firsthand

Boost leak test (good maintenance)
Test ISC coils
Take off throttle body and clean the hell out of it with WD-40 etc
Check/set TPS

The BISS is set from the factory and unless it has been tampered with before there is no need to adjust. Not a good idea to even attempt on a 2G without DSMlink or the dealers expensive ass equipment anyway

http://www.youtube.com/watch?v=KibYz21IMA0

 

[007jimmy]

Uh no don't touch the BISS firsthand

Boost leak test (good maintenance)
Test ISC coils
Take off throttle body and clean the hell out of it with WD-40 etc
Check/set TPS

The BISS is set from the factory and unless it has been tampered with before there is no need to adjust. Not a good idea to even attempt on a 2G without DSMlink or the dealers expensive ass equipment anyway

X2... Most likely a boost/ vacuum leak. Dont touch the BISS. But... You might have to if a boost leak test shows a leaky BISS o-ring...

 

[NHerron]

True that... in that case, count how many turns it takes to fully seat the BISS, then remove and replace o-ring. Then screw in and fully seat BISS and turn out however many turns from before

*Whoops typed to fast*

 

[miguelmcv]

Boost leak will bring the idle up and not down, However, is good to do a boost leak for peace of mind.
You don't need Link to adjust the biss, as far as you get zero boost leak and ISC working good, then the biss is easy to adjust.

 

[NHerron]

For '97-99 YES, yes you do.

If you can permanently set your idle with the BISS that means the ISC is out of it's adjustment range. The BISS is set so that at idle the ISC is in the middle of it's range so it can adjust 50% one way or 50% the other. Notice the engine changes it's RPM's for a couple seconds and then resets back at 750 rpms. The ECU wants 750 +/- 50 so it does so by commanding the ISC to open more or less one way or the other. If you *bandaid* the idle by opening up the BISS more until the idle is where you want it, you have no idea where the ISC is at without a logger.

Dealer-
1G BISS Adjustment

DSMlink-
http://www.dsmtuners.com/forums/newbie-forum/321158-biss-adjustment-iac-position.html

 

[herms99gst]

Low idle will make your idle rise not fall. Boost leak is a good idea but like stated...clean your throttle body with brake clean or equivalent. And clean the iac. Let the tb and iac dry good before you reinstall it.