2001 XJ rough idle at start up.

[trevhutch]

Now the check engine light is staying on.Engine idles at about 500 -600 rpm.38,000 miles on the engine(4.0l).Any help or suggestions would be great!

[Bounty__Hunter]

IAC (Idle Air Control) motor needs replaced, or the IAC housing cleaned at a minimum. Could also be the TPS (throttle position sensor). Run it by autozone or somewhere and have them check the trouble codes, it's free.

	Throttle position sensor A throttle position sensor (TPS) is a sensor used to monitor the position of the throttle in an internal combustion engine. The sensor is usually located on the butterfly spindle so that it can directly monitor the position of the butterfly throttle valve. The sensor is usually a potentiometer and therefore provides a variable resistance dependent upon the position of the butterfly valve (and hence throttle position). The sensor signal is used by the Engine Control Unit (ECU) as an input to its control system. The ignition timing and fuel injection timing (and potentially other parameters) are altered depending upon the position of the throttle, and also depending on the rate of change of that position. For example, in fuel injected engines, in order to avoid stalling, extra fuel may be injected if the throttle is opened rapidly (mimicking the accelerator pump of carburetor systems).

[trevhutch]

Thanks!!

[IcyFridge]

I have similiar problems with my01. It idles lopey for a minute and then goes back to normal. Happens like every month starting up.