Engine Gremlin

[96Br0nc0Guy]

96 E.B. with 351.
Throwing Codes 171/174 (Bank 1/2 Lean).
Took it to shop, they smoke tested and fixed vacuum leaks.
Have replaced the following:
PCV, EGR, MAF, temp sensor, air filter, all three O2 sensors.
The shop guys and I are stumped...
All thoughts or suggestions greatly appreciated.

 

[Tiha]

Weak fuel pump?

There used to be a flow test to do on the pump and it was much more telling than just a pressure test.

It can provide enough pressure but if there is a restriction like a plugged filter it can still be starving for fuel.

 

[L\Bronco]

Good call Tiha!
Pump volume spec is 1quart in 30 sec minimum.
They had an issue with O2 sensor ground issues as well