Car dies when idling at stoplight

I have a 1999 Saturn SC2 with an automatic transmission. Lately, it has been turning off when I come to a stoplight. It has only done this a few times and is not constant. It also has only started hapening since it has gotten a bit warmer. It doesn't seem to do it at night, though. My AC has been running when it happens. Also, my engine makes a rattling noise when it passes 2000 RPMs or when I first start the car. Does anyone have a clue as to what it could be? Can I fix it myself?

Is the idle too low? When the AC comes on, the idle should kick up about about 100 rpm. Is the vibration at 2000 rpm only with the AC on? You might have a compressor that is about to fail. Get it checked out before you loose it when you need it most.

Oppie