All, looking for some insight. 2007 5.4 3v super crew. I have been chasing random issues for about 3 years now, but a new one popped up today. The wife came home today saying that the truck is running like crap, major hesitation when pressing the gas pedal. I have had random hesitation issues, but nothing like this. Forscan showed 2.7v on the fuel pressure sensor with normal kpa readings.... I'm not positive that it should be 2.7v, and the voltage does drop when hitting the gas pedal. Once I shut the truck off, it didn't want to start. I pulled the front O2 sensors thinking it might be a plugged cat... that didn't work. I then found very erratic readings on the fuel pressure sensor.... in the neighborhood of .45v, kpa was 0. I changed the pressure sensor, no difference. Confirmed 5v at the pressure sensor connector. Swapped the FPDM, no change. Jumpered the connection to the fuel pump and confirmed the pump is working. At this point, Forscan shows the fuel pressure sensor voltage swinging anywhere from .2v to 2.36v erratically. Pressure is also changing erratically. I have a lot of the cabin wiring out of the truck for inspection, no issues found so far, I did just notice that with the key in accessory mode for Forscan to run, the voltage drops from over 12v to 11.6v almost instantly when I turn the key. I'm feeling like there's a direct short somewhere.... any thoughts? I should also mention that I currently have the connectors on the frame rail disconnected, so it feels to me like that negates any of the wiring past the engine bay. Maybe?

 

Code test with a conventional scan tool that shows PIDS
Fuel pressure Kpa was what?
Are the O2 sensors switching?
Check the grounds under both kick panels quick

 

Update: I spent the last 2 days digging into the wiring and did find some wires with wear on them on the passenger side by the firewall. Repaired those, and worked all connectors until they locked. Finally got the erratic measurements to calm down and the truck finally started…. Only to find a worn o ring on one of the injectors spraying fuel everywhere.

its back together, seems to run. Need to clear the codes and see how it settles out.

 

What is your running fuel pressure? It should be 38-40 psi and steady.
Check the ground wire 10" away from the FPDM