97rebuiltZ28

Hello All, My Z28 has started stumbling on longer drives, ie 15-20+ minute drives, I plugged up my live scanner and quickly went through all the live diagnostics and noticed that the IAT temp was 116 degrees. I drove it for a second to see if it would go up or down and it stayed around 111-116. I’m curious if any of you have seen what your Idle Air Temp registers after your cars have been running for awhile,(15 minutes plus).

Injuneer

The IAT sensor tends to heat soak from under hood temps, indicating higher than actual ambient air temp. On a hot summer day, A/C on, sitting in stop & go traffic, I've seen the IAT reach 140°F. I relocated the sensor to the end cap on the filter of my cold air intake and it read closer to ambient.

I've also reviewed 100’s of PCM data logs for people, and the problem shows up at idle and low speeds, but temp typically tends to drop as the engine RPM and vehicle MPH go up. I would expect yours to drop like that, but I have no idea what the ambient air temp was where you were driving, or how fast you were going.

Unless you have a 1993 running speed-density (no MAF sensor), or if the MAF sensor fails and the 94-97 PCM defaults to speed-density, IAT is not all that important. I did feel that when I got the 140° reading, the idle seemed rougher and the power off idle seemed down slightly. My thought was the PCM was pulling a bit of timing to prevent detonation, but I was never able to confirm that.

97rebuiltZ28

Thank you Injuneer, that’s what I needed to know.

Injuneer

PS: It’s INLET (or INTAKE) Air Temperature.

terminal_crazy

When i’ve been playing with my ‘95z i’ve found if i stop the car and restart once warm, it’ll run a few points leaner then richens back up slowly as the iat starts to drop. I’m not sure why it should affect the tune that way but playing with the tables doesn’t seem to make much difference either.
Mitch

97rebuiltZ28

Thanks for the correction, I guess I was thinking of an IAC