[Iroll240]

So, it's back- a 250A code and a p0171 right bank too lean code. I have replaced the fuel pressure rail sensor with a new Bosch, the MAF sensor with a new Denso and the valve cover to PCV flame trap hose and erased the OBD II and disconnected the battery, which kept the check engine light off for a while (under 60 miles before it tripped). Red flashing codes on my OBD reader were down to only evap, with no check engine light on. So had my son drive it for a while in hopes of getting that stored OBD evap to go to green. then the check engine light came back on while he was driving it. My question is, what do I try now? thanks in advance for the advice! .

 

[avenger09123]

Start simple - when was the last time you changed your air filter?
Assuming your MAP is good,
Then we look at O2 sensors - Are they reading correct at idle and while moving?

 

[Iroll240]

Back on with P0171 code after the front O2 sensor changed. this is really driving me crazy!

 

[02Pilot]

DTC Decode lists the following possible causes for ECM-250A (Long-term Fuel Trim (Upper Limit Or Lower Limit)) :

• Upper limit:
• Incorrectly installed oil dipstick. Air leakage.
• Too high ethanol content in fuel.
• Air leakage in the intake system.
• Air leakage in the exhaust system.
• Low fuel pressure.
• Damaged mass air flow (MAF) sensor.
• 
  
• Lower limit:
• Oil level too high.
• Contaminated engine oil.
• Leaking injectors.
• Damaged evaporative emission system (EVAP) valve.
• High fuel pressure.
• Damaged mass air flow (MAF) sensor.

Assuming yours is an upper limit case (based on the P0171 lean code), I'd be looking for a vacuum leak. Smoke test is going to the be the most expeditious way to find it.