Have a 04 gt auto with 70k on it. Keep throwing code P0316 (misfire under 1000 revolution on startup) and P0171(fuel pressure bank 1) and now its throwing P0305 (misfire cylinder 5). All spark plugs are new. Changed injector. Change coil pack. Changed fuel rail pressure sensor. Even change the o-rings on all injectors. Had a bama tuner on it. Fuel pump duty cycles were good so dont think its the pump. Thought it might be the tuner throwing the pcm off. So rest the tune to stock and it still does it. Runs great but it has hard starts once in awhile and that is when it throws the codes. It will clear the check engine light by its self and then it gets the codes again. If anyone has any idea or has heard of this please help. Tired of chasing my tail.

 

Are the hard starts after it sits for a while or on particularly cold/hot days?

 

i drive it everyday. So it doesnt set for long. Had both hot and cold days in the past month and it hasnt made a difference. Its seems completly random.