I thought I'd give an update on my 1998 Trooper check eng error codes (P1171, P0137, P0157). These all have to do with the engine running "lean" during hard excelleration. The P0137 is one of the rear O2 sensors reading lean and the P0157 is the other side rear O2 sensor reading lean.

Here is what I have done so far:

1)Replaced fuel filter (cheap)

2)Check fuel pressure (on rail) and reading 33 to 38 psi (book say it should be 44 to 52)

3)Replaced Fuel Pressure Reg. (now reading 38 psi at idle and 42 with pump turned on but engine not running) Not sure why pressure is not within spec...any thoughts?

4)Checked fuel pressure (on rail) with return hose squeezed off with plyers. PSI goes up past 60 right away....seem fuel pump is not the problem.

5)Replaced rear O2 sensors (both sides)

6)Replaced Intake Manifold Gaskets (old ones "looked" fine).

After each repair I've cleared the CE codes and taken it for a spin and when I stomp on the gas imediately the CE light come on and gives the same codes. I noticed one of the fuel injectors sucking air (I suspect this is from disturbing them while changing the IMF gaskets). I've order a new O rings/seals and will replace these tomorrow. After that I've run out of things to try.

Any suggestions from out there or is it time to admit defeat and bring it to the dealer?

Thanks

Mike