I'm at a loss

[jwt40]

Hello all, I have an 04 expedition 5.4 Eddie Bauer with over 287,000 miles on it. I can't keep it running for the life of me. It just chugs and dies. I thought it was the bank 1 catalytic converter so I had that replaced and it didn't fix the problem. It was throwing codes for the o2 sensors on bank 1 so I thought the converter was clogged. I've checked the pcv valve and it's good and I can't find vacuum leaks anywhere. I will mention that both o2 sensors on bank 1 are brand new and after they were replaced, they were throwing codes saying they were stuck lean. Im relatively new to expeditions in general so im learning as I go. Any advice on what to look for or what to do would be greatly appreciated. Thanks!

 

[AWAR]

Fuel pressure issue? I am replacing the injectors on my 03 Navigator this week.
Put a fuel pressure gage on it and check pressure and flow. Key on engine off should be about 39psi. There is a filter next to the tank ahead of the driver’s side rear tire. The cover over the filter is difficult to remove, plastic is getting brittle on our old rigs.

 

[Gary Waugh]

I would be checking your fuel pump and fuel line pressure first. A failing fuel pump will cause all the issues you describe and is an easy fix, you can usually rent a fuel pressure tester at autozone and check the pressure in a minute.

 

[kep5niner]

Intake manifold. What specific codes are you getting as well?

 

[texasscot]

As a possibly failing fuel pump is being mentioned as a cause i'll throw in the failing fuel pump relay as a potential also.