1G IDLE SURGE and the ISC isn't the problem??

[tsi1991awd]

Alright here's the problem...I have been having an idle surge issue when the car warms up ONLY. I thought it was a bad ISC EVEN THOUGH the ISC tested out fine.

I bought a NEW OEM ISC and installed it....SAME PROBLEM. When the ISC is unplugged, the car idles at 1200. This is WITH THE BISS SCREW all the way IN. When the ISC is plugged in, the idle surges again between 1500-2000ish.

What could be the problem?? Has to be something to do with the ISC or something.

 

[92AWDHX40]

Terry's Talon Troubleshooting Tips #3 - Fast Idle (aka. Idle Surge) Here you go, this should be more than enough for your questions, start here first.

 

[LiquidX]

You need to set the BISS properly and allow the ISC to work properly in a specific range of movement by grounding out the diagnostic pin and set your idle via BISS.

Turn and wait a min for the ISC to move as well.

A bad FIAV will cause surge and so will boost/vacuum leaks. A bad TPS can cause surge as well.

 

[tsi1991awd]

I grounded out the timing connector and diagnostic terminal under the dash. Started the car and there was no change in idle whatsoever. It still surged.

I adjusted the BISS screw in/out and idle did not fluctuate at all.

Could it be the ECU driver for the ISC? I JUST got this back from ECMTuning because they did the eprom conversion and replaced the caps. I would think they would've caught it if the driver was bad but....