Celica Forums General Discussion Engine and Performance Low idle when stopped in gear

My wife's 2002 celica GT (Auto trans) with 96k miles has been idling low when stopped while in drive or reverse, but not when parked.

When parked it sits around 8-900 rpms once fully warm, but in drive while stopped it's more like 4-500 rpms

This all started after we had a -30 degree cold snap here in MN, and it had a rough start after weathering that (was still -15 when started).

Tried resetting the ECU (is 5 minutes disconnected from battery long enough?), but no luck.

I've read about other stuff like mas airflow sensors and idle air control valves being dirty causing the issue. Could it be one of those? Do either of those act up post deep freezes like I had?

If it is one on those, is it safe to let it go for a couple months /8k miles or so (wife drives 500 a week for school)? I don't have a warm place to do any of that work myself.

I have a similar problem. Mine idles around 1000, but dives below 500 sometimes. It does it religiously if the air is blowing and the engine is cold. The "trick" I've been using is just to play with the HVAC till it behaves, or ignore it and start it back up if it dies on me...not much of a trick TBH. Haha.
If i were you, I'd replace the IAC valve and clean out your throttle, THEN reset the computer. See if that helps.

Too cold here in MN to do that right now. Hoping it'll be fine for couple months/4k or so more miles