So recently i bought a 2004 f150 lariat 5.4l 3v. Has 188000km was owned by an older gentleman. After having it for a few thousand kilometers it started to buck and surge under acceleration, it got worst when i had to drive in the rain for a few hundred km. I did some research on the internet and thought i had it narrowed down to the fpdm, i replaced it and was rotted very bad. Thought that fixed it. Drove 60km without issue and then on the drive back it started to surge as i tried to give it gas going up the hill. The time in the rain when it was bad 3 codes popped up, lean on both banks, p0174 p0171 and another one i cant remember at the moment. That what gave me the idea it was the fuel module. After replacing it i now have the code p0191 popping up, fuel rail pressure sensor. With more reading into the issue, i narrowed it down to a junction under the driverside door on the frame or my tps is bad. Any input would be appreciated, also was wondering since i didnt disconnect my battery after replacing the fpdm, wondering if that could be a problem. Usually doesnt happen until its up to working tempature, i can push on the gas in park and neutral without issue. also if i turn the truck off and then fire back up it wont act up until a few km. Im puzzled at the moment. will a bad tps mess with the amount of fuel going to the rails?

 

I would look at fuel pressure. Might be the fuel pump going.

 

I would look at the fuel pressure. Could be the fuel pump going.

 

Fuel pressure is dropping yes, the sending units are not common on going. These trucks have no return fuel lines, the fpdm controls the duty cycle of the pump.

 

Sorry for the double post. The app isn't acting right at the moment.

 

No problem, thanks for suggestion. I hope it ends up not being the sending unit.

 

Maybe the fuel filter hasn't been changed. I'd probably start there. That would be the easiest fix. Good luck.

 

Yeah I was thinking the same and changed it, at the moment it's freezing out and I am away at school. Can't have the truck down because it's y daily driver or I would tackle plugs and coils.

 

Have you replaced the plugs and/or COPs ? That could be an issue as well

 

If I wasn't throwing low fuel code I would suspect that.