OK guys new to the forum but on a few others. I have a 2001 Jimmy SLT 4x4 215xxx miles. Truck ran great until recently I started noticing a bucking and jerking at about 50-55 in OD. Then that proceeded to get worse and turn into a backfire/misfire and sputter randomly at different speeds rpms followed by hard starting.
First guess was pressure test it. On the test I got 55 turn key on and leak down to 35 in about 5 min. Immediate leak of about 10 psi within 10 seconds. I proceeded with replacing the pressure regulator. After that car ran fantastic no misfires (Snap on Solas scanner) no codes. Did injector tests and everything was good. Soon as I hit the highway later hauling my boat started doing it again. Same symptoms. So I had him throw in a different set of injectors that we know were good with about 140k on them. Again truck ran great for a min but started acting up again soon after.
I have already replaced fuel filter, cap, rotor, plugs, wires. Had pressure gauge while driving and during misfire periods the pressure remained at 60psi while driving so I ruled out the pump. There are no leaks and I dont know where to go next. Code I get is a general misfire p300 code. I just figured I would ask before buying a 250 dollar fuel pump after all ive spent now. Some days it will drive great and others not great. It seems the problem clears up a bit if I let it idle for 10 min before attempting to drive. No difference hot or cold just random everyday.
Thanks for any and all help, sorry so long just trying to be as detailed as I can.
First guess was pressure test it. On the test I got 55 turn key on and leak down to 35 in about 5 min. Immediate leak of about 10 psi within 10 seconds. I proceeded with replacing the pressure regulator. After that car ran fantastic no misfires (Snap on Solas scanner) no codes. Did injector tests and everything was good. Soon as I hit the highway later hauling my boat started doing it again. Same symptoms. So I had him throw in a different set of injectors that we know were good with about 140k on them. Again truck ran great for a min but started acting up again soon after.
I have already replaced fuel filter, cap, rotor, plugs, wires. Had pressure gauge while driving and during misfire periods the pressure remained at 60psi while driving so I ruled out the pump. There are no leaks and I dont know where to go next. Code I get is a general misfire p300 code. I just figured I would ask before buying a 250 dollar fuel pump after all ive spent now. Some days it will drive great and others not great. It seems the problem clears up a bit if I let it idle for 10 min before attempting to drive. No difference hot or cold just random everyday.
Thanks for any and all help, sorry so long just trying to be as detailed as I can.