Achieves Running Temp, Then Spits, Put In Drive And Stalls, Wont Start.

on cold start it runs great. as it gets up to running tempature it coughs a few times and picks up a miss. when u put into drive, it stalls. you go to start it up again and it wont, jus rolls over. it has spark, unsure if it is getting fuel. the pump is kicking on and when you depress the fuel rail access it sprays fuel. idk y its not firing or running. it died on me and i towed it home after the first incodent, wasnt sure if it would ever start again. well, in the morn i checked to see if it would start again. it did, jus fine, ran great until it was reaching normal running temps. i have no codes. it jus gives me code 12 which is self test indicator. so, any ideas of what the cause is????