I have an 01 GTP, for a while now after driving for an hour or longer, my car will start shifting strangely or not at all, just rev up under accelerationa nd not shift, I thought this was a trans issue, but it persisted even after I bought a brand new trans from TEP (not for this issue) but the car still does this, I had a retune from ZZP to correct my MAF for the Northstar throttle, issue has persisted, finally one day I bought a pressure tester and the car was idling with 30 psi after driving for over an hour and the psi dropped with any increase to rpm, I bought an AEM high flow in tank fuel pump and the car seemed to be doing fine at 60 psi idling with no change with rpm increase. A few hours later I get stranded and the fuel line in the pump busted in half, put a new line in and the car now was idling at 120 psi at the fuel rail. Put a different pump is and the car was still at 80 psi, put the aem pump back in and blew through the return line only to have no luck. I replaced the stock fuel rail on the car with a spare fuel rail i ahd laying around off my 97 GTP, and the car went back to 60 psi at idle.
Now a week later the car started surging at idle and taking 2 attempts before it would start, and each the engine would turn over 10 times before it would actually start. Checked and the rail had 120 psi again, so took the fuel pump out and the hose looks like it started swelling so much it broke the outer braids off of it, replaced the hose and the car went to 60 psi, turned the car off and back on, 50 psi, off and back on, then it stayed at 40 psi and fluctuated constantly by 5 psi. Next morning I get stranded on my way to work because the line was pushed off the pump, put the line back on and a mile before my house the car starts stuttering and the o2 voltage was at 30 and stayed there for the last mile.
I don't think it's the pump, but the pump is getting 13.6 volts to it consistently with stock wiring, replaced the relay and made no difference, the car fluctuated by 10 psi removing and reattaching the vaccum line to the pressure regulator, lines aren't clogged, fuel filter is new, and I can't find any resistor for the fuel pump, car only has issues after driving for an hour so I think it's something electrical heating up, but there isn't any resistor in the front end of the car. I ordered a stock replacement pump from Amazon that will be here tomorrow and I will see if it helps, but I'm running out of possibilities and don't know where to look.
