Hello All,

1998 ranger 4.0L XLT Supercap 4x4

Throwing CEL for P0171 and P0174

Things done:
-all O2 sensors 1 yr old
-S-Plugs only 6 months old
-Fuel filter 1.5 yrs old
-Replaced fuel pressure regulator thing
-Cleaned mass air flow sensor
-Cleaned IAC valve
-Mass Air reading correctly when connected to computer
-Checked for vaccuum leaks all around truck found small one in lower intake manifold
-Replaced upper and lower intake manifold gaskets and valve cover gaskets and reassembled... changed oil etc...

Still throws boths codes

What is the spec on the fuel pressure at the rail?

I have seen that it was something like 48 psi +/-12 psi but not sure..

I have 34 psi on the rail.. Is that low fuel pressure enough in itself to throw lean codes on both banks?


Thnx in advance for any help!