Camarochriss

My 2000 Z28 M6 with 90K miles idles high (1100 or so, vs the usually 700) but only when the car is warmed up, and only during the summer months when we're over 80 degrees or so.

Towards the end of last summer I:

1) Cleaned the throttle body and MAF.
2) Replaced the Idle Air Control sensor

That seemed to fix it, but now I realize it was probably a temperature thing - it was fine during the fall winter and spring, but now that it's consistently hot again, I can't go more than about 10-15 minutes of driving before it starts to idle high again. I re-cleaned everything, including the IAC sensor, but still getting the issue.

What should my next step be? Replace the TPS?

Car isn't throwing any codes, but sometimes it almost feels to hesitate for a split second during acceleration.

Thanks!

G Atsma

Does this actually only happen when the A/C is on? The ECM might be over compensating for the RPM drop that normally happens when the A/C compressor kicks in. Just a thought....

Camarochriss

I thought that too at first, but it does it regardless of having the A/C on or off.

G Atsma

Sounds like it's only doing it when going closed-loop, after it warms up. The intake air temp sensor might be defective, and not reading correctly when very warm, possibly causing a calibration error somewhere else. I don't know if the IAT would throw a code in such a situation. Just my .03(inflation, lol) again...

Camarochriss

Thanks! Hadn't thought of that - I'll try swapping it out.

Camarochriss

Ordered a new IAT sensor last night, got in this morning and she threw an SES - for the TPS, gonna swap that out today and see what happens.

Camarochriss

Replaced the TPS today and it runs great now - thanks for the input! I'll hold on to the IAT sensor for a bit to see if it acts up again.

G Atsma

Hey, glad you're going again! I think the main deal with all this stuff is to follow a logical sequence. It worked!