sjdhammer

my 2.4 wants to idle at 1500 to 2000 rpm.

I have done all the usual, cleaned the throttle body, made sure that the IAC is seating properly, replaced the IAC valve since I managed to break it, replaced the MAP sensor because it was cheap.

I can adjust the IAC valve to make it idle at about 700 rpm and it will stay there for one on off cycle of the ignition then it goes right back up.

Take it off and the IAC valve is screwed in accounting for the high idle.

No trouble codes present with hand held (not fancy scanner.

Was told it might the the Coolant Temp sensor. Where is it located on this engine and does anyone else think this might be the cause?

Thanks

Steve

EinST

The ECT is located at the coolant inlet (rear of the engine, i.e., driver's side, follow the hose). I doubt it has anything to do with your problem, though. What led you to break the IAC valve?

sjdhammer

My clumsiness caused me to drop then step on the IAC.

Anyone have a suggestion as to where to look?

Thanks again.

EinST

No,, I was asking why you even had the IAC valve out. Were you working on this same high idle problem?

sjdhammer

Had the IAC out to make sure there wasn't a piece of carbon holding it open per the suggestion of someone who repairs cars for a living.

EinST

Okay, so you had the same high idle problem prior to that incident. It sounds like the PCM is trying to compensate for either too much fuel or too much air, based on the O2 sensor readings. Try unplugging the MAF sensor and see what changes it makes to the idle. Also, get it scanned for short term/long term fuel trim values. It'd be even more helpful if you could post the snapshot data.

loosebearing

coolant temp sensor

sjdhammer

Thanks
Will try the maf sensor.

Is there a voltage output spec that I can find for the CTS?

EinST

The ECTS has to be looked at as a whole thermistor circuit, i.e., it's more often a wiring problem than the ECTS itself. Plus, the PCM will detect certain ECTS failure modes and throw a code. I'd scan for what the PCM thinks the coolant temperature is and sanity-check that.

Jing

I have the exact same issue with my 02 Cavalier Z24

I have tested the O2, maf, and we have tested coolent sensor... I have also checked the throttle springs to ensure it wasn't holding it back...
the only difference from what has been described here is that when driving, and you get teh engine to say 4,000 RPM it randomly locks at that rev while shifting up... if you press the excellerator while the clutch is in it will go to say 4500 and lock there... and you basically have to ride the clutch to have it drop the RPM... no codes are thrown at all. the only thing i have not tested is the actual computer controller...