jkm757

My 98 GT will not idle at the proper RPM when the engine gets up to operating temp. Normally it idles around 800 RPM when warm, now it's under 500 and I have to keep my foot on the accelerator to keep the engine from stalling. What ever is causing the problem does not trip the check engine light. Any ideas you may have as to whats causing the problem are greatly appreciated. Thanks.

CalBoy101

Could be bad IAC valve, bad IAT sensor (intake air temp), ECT (engine coolant sensor), TPS (thottle position sensor), MAF or a sticky EGR valve, when they stick open they cause idle problems.

Do you have a way to datalog and see what values you are getting from the IAT, ECT, MAF and TPS sensors?

You should also check the fuel pressure.

dawson1112

Sounds like a dirty IAC . Mine idles at about 1000rpm until it starts to warm up then settles at 800.

jkm757

Thanks CalBoy. I'll check the valves and sensors you called out. The car has 175,000 mi. and other then the ECT, all the other sensors and valves you mentioned are original. I do have a code reader to get data codes but I don't have a scanner to read real time telemetry.

jkm757

Thanks dawson. I'll look into the IAC and see if that's where the problem lies.

uberstang1

check the iac