Stumble while idleing...

[WhtHotZ28]

My car seems to be stumbling at idle. It happens usually in the afternoon when it gets hotter. It seems the idle falls too low then it revs higher to not stall. Could it be time for a plug change or is this the symptoms of something else.

Thanks in advance,
Chris

[Joe 1320]

My bet is on the IAC valve. That is the idle air control valve screwed into the TB. It is directly responsable for metering air when the throttle blades are closed and directly affects idle quality. If you have no other symptoms, then that's my bet. It can be removed and cleaned to see if there is any improvement.