When the engine is cold (the car has sat for maybe 4-8 hours) i have to turn the engine over multiple times before it will start and stay running. It will turn over, then start and die instantly untill it stays running. Once it's running it does okay, however the RPMs will randomly dive down to like 400 and when i go to accelerate faster than just a steady take off, the engine will kind of choke out and hesitate. the check engine light gives the code for the fuel system/heated O2 sensor. O2 sensor is brand new and the Relay/fuel pump both work. Any thoughts as to what else it could be?

 

COIL PACK. I'm 95% sure its coil pack. Did it just start in colder weather? Check out in your primary and secondary coil resistances if you have an ohm meter (.6 ohms and 18k ohms, and you will need to refer to workshop manual to know which contacts to measure to read each coil's resistance.)

O2 code, I think means your running rich, which means I believe your not getting enough spark to burn off all the fuel. If thats not possible some one correct me, but this is what I personally experienced and after I swapped coil's it all went away.

Your Symptoms are EXACTLY what I went through, so I changed my coil pack and made sure all the contacts were clean (to primary and secondary coil), and the ground that goes to the Distributor. Also, make sure your ICM connectors (in your distributor that you see beside your roter after you take off your cap) are clean and making good contact with connectors. If you can pinch the clips at ends of wires to make sure they bite down on the blade contacts.