1999 Expedition 5.4L 4x4

I have code P0175 (Bank 2 Too Rich) code.

I replaced HO2S21 (Heated O2 Sensor Bank 2 Upstream). The O2 sensor switches but the rich reading is off the charts, always around 1666Mv while the lean reading looks normal when it switches. These are the same reading the old O2 sensor showed so I know its not a sensor problem.

I checked my fuel pressure at the rail with KOEO and I was at 38PSI.

With KOER the pressure dropped down to a consistent 28-30PSI which I feel confident is too low for the engine.

If I remove the vacume line from the fuel pressure regulator, the pressure jumps up to 40PSI and stays constant.

What would cause the fuel pressure problem and why would I have a rich condition with low fuel pressure?

Any help would be appreciated.

 

I think if you posted this over on the EXPY board you might have better luck in getting an answer. I don't have a computer Fords. Mine are GM & Jeep.