Help with fast idle.


Jeep Newb
01 XJ with 4.0L
Hey! Just put it all back together after replacing the head gasket. Was very happy to hear her turn over and purr to life. Then the engine started racing as if I had the accelerator on the floor. I shut off the engine when it hit about 3k rpm. I never touched the gas.

started it a few more times with thesame result. Checked throttle linkageand they seem fine. What am I missing?


Staff member
I'm not the best expert here, but on my 4.0 when it did that we found bad wiring at the Throttle Position Sensor (TPS). It was actually kind of loose at the fitting/connection too. Well, then there was the time on the Rubicon when it was doing that and my floor mat was jammed up into the throttle linkage somehow...
IAC needs to be cleaned. DO NOT get one from Auto Zone. They are too long and will not ever seal resulting in high idle. Dealer is best option Ive found.