My engine starts fine but after a while it shuts off by itself. Only happens when I don't touch the throttle, the rpm's just drop and the car stalls. What could cause this? Battery and alternator are fine.

 

Could be a number of things:
- clogged CAT
- clogged fuel filter
- clogged fuel injectors
- Significant vacuum leak
Make sure all of the simple tuning things are set first. Plugs, wires, timing, TPS adjustment, Idle speed setting. Then I would eliminate vacuum leaks. Start & stall can be time consuming to find and fix.

 

reading this makes me sad, i have the same problem. better get to work...