speed43

My car has had this problem were the idle drops and almost turns off. But it bounces right back up. Yesterday I was looking under the hood (car was running) and all of a sudden the air pump turns right on and the engine almost turned off. Than the air pump turns off and the engine goes back to normal. This was like a split 2 seconds that the pump turned on n off which caused the engine to almost turn off for a split second or two.

Any ideas why the pump turns on n off like that?
The car was fully warmed up after driving 2-3 hours..
The air pump does turn on every morning when I first start the car (which is normal) but after a little while it shuts off (normal). But it turning on n off real quick after 2-3 hours of driving should not be normal. Right?

What can I look/check for that may be causing this?