idle problem pls help

[ifinessei]

Ok i just bought a 92 talon tsi awd with 109k miles on it a week ago.
I had driven it but not really hard. When i got to my house i opened it up a little. then i noticed an idle surge. it goes from around 1400 and drops to 1000 then back up to 1400 then down to 1000 and so on. when it cold starts it has no problems only when its warm will it surge... is it a vacuum leak or 02 sensor or sumthing else pls put ## input thx

 

[tmoore8828]

The first two items you may want to check are the BISS (Base idle set screw) and then the IAC (idle air control) valve.

1.)The BISS is on the throttle body under a little rubber plug (if yours still has it).
the common problem there is a damaged oring. If it does leak, it will cause idle surge.

2.) Another common problem is the little stepper motor under the throttle body called the IAC. It moves a little valve body in and out to control the idle. You can check it by simply removing the plug and checking resistance across the coils. They are a common failure item and can be found at a scrap yard or on EBAY for $20-$40.

If you do a search for IDLE SURGE you will probably come upon a good test procedure for the IAC. If you can't find one drop me an IM and I'll dig out my manual.

 

[EclipseGSX012]

yeah check for vacuum leak