My 2000 4Runner SR5 has been stalling lately when the car is warmed up and sitting idle at a stop light. I only does this once in a while. (4 times in the last 2 months)

Also, perhaps not releated, my Check Engine light comes on and off from time to time. NOT at the same time as the stalls. I have had that check and my mechanice said it may be a bad sensor because the computer is not registering any problems.

What could be causing the stalls?

You may have a dirty MAF (Mass Air Flow) sensor. It's a sensor that's right behind your air filter and it's really fragile. Just be careful when you're cleaning it.

Try cleaning the inside of throttle chamber where throttle valve closes to restrict airflow at idle(sometimes it gets sludge/grime built up inside and does not let enough air by plates at idle when dirty and causes this problem...goodluck

Try cleaning the inside of throttle chamber where throttle valve closes to restrict airflow at idle(sometimes it gets sludge/grime built up inside and does not let enough air by plates at idle when dirty and causes this problem...goodluck

Yea, what he said too. :shakehead
Try both of those things. It should smooth out idle quite a bit.