Intermittent stall-looking for advice!

[SeattleJen]

Hi! I am dealing with an extremely frustrating issue with my 1998 Corolla CE (about 101,000 miles, so NOT ready for the scrap heap)! About two months ago the car stalled at a red light-no engine code, just as if I turned the engine off. It did start back up again. This happened a few more times. My boyfriend did a significant amount of work on the care (listed below) and a mechanic looked at the car and tested the ECT sensor. He could not replicate the stall.
No stalling at red lights for a couple of weeks now, but it still stalls when turning the wheel all the way to one side at slow speeds (like backing up out of a parking spot). This just happened while getting snow tires put in.
The weather is getting darker and colder and I am now scared to drive the car-Seattle drivers are NOT pleasant if your car stalls in front of them at a light. Also, my car is a lot smaller than most other vehicles on the road-really don't want to get rear-ended.
Here's what has been done:
MAP sensor replaced
Spark plugs and PCV valve replaced
Throttle body and IAC valve cleaned (IAC valve was not very dirty)
Air filter replaced
ECT sensor tested
Battery and alternator tested
I am wondering if there is any way I can check to see if the IAC needs to be replaced-it's not cheap and I don't want to just replace it randomly. Also, is a genuine Toyota part necessary?
Would appreciate suggestions-thanks so much! The car always starts fine, ONLY stalls at idle, and is generally fine once warmed up.

 

[goku]

Try banging your hand on the steering wheel or jiggling the key in the ignition switch. It's possible a loose/weak connection in the key ignition is causing the car to turn off. Try tapping on the brakes for the brake light to come on and see if that causes it to stall. See if the condition can be replicated when in park, or if lights are on, fan blowing, etc.