it starts with a bad miss and wont keep running

I'm working on a dodge intrepid, it starts and runs with a bad miss and wont keep running, after a while it will just turn over but not start. This all started when the head gasket blew. I changed the head gaskets, hooked everything back up right I checked the fault codes befor starting it up it only 12, 55 to me that was ok. I double checked everything and it was good, has anyone had this problem befor?

Not only that, to test the computer I unpluged some sensors and checked the codes again and still 12, 55 shouldn't the computer give me codes for that?

ok, couple of things, which engine is it? Is it a 93-97 1st gen or a 98-04 second gen? The reason why I ask this is if you were working on a 3.2/3.5 V6 on 1st of 2nd gen Intrepids, you would have to remove the timing belt to take off the cylinder head (same with the 2.7 on 2nd gens). From what you describe, I would double check the timing of the cam gears making sure that they didn't jump time. You can easily check that by doing a compression test.