2000 Dodge Stratus Engine died, replaced distributor, now r

I have a 200 Dodge Stratus, 6cyl. The check engine came on and went off a few times and the engine would skip just a little while driving on the highway. One I started the car, it started for a few seconds and died. Towed it to a mechanic who replaced the fuel pump, them the crank shaft sensor, but still didn't start. So I towed it to a dealer who replaced the distributor. The car now starts and runs, but runs very rough. When idling the RPMs go from very low to over 2,000 and back again over and over. When I drive it will sputter and every now and then die and I have to restart it. The mechanic at the dealer said it maybe the crank sensor...
Any ideas as to what is could be? Thank you.