P1131 Code

[nscelzisr]

2000 Ford Ranger Supercab XLT 2.5L Manual Trans-

Recently purchaced. Truck bogs randomly through all gears then regains power. Happens when cold or at operation temp. Sometimes idles rough. No stalling. Doesn't sound like a misfire. CEL Came on and pulled code P1131 Bank 1 Lean. Changed oil and filter, changed thermostat and flushed all cooling system, changed fuel filter, replaced broken PCV Hose, changed air filter, inspected all vac lines. Plugs and wires look new. Reset Code and CEL came back on and then off. Still running like this. Not sure what else to do without throwing random parts that I've read in other forums.

 

[RonD]

I would check the EGR valve(remove it) and system, this is something that can be checked and cleaned without spending $$, and can cause the symptoms and P1131 code.

How many miles on the motor?

This is a good read about the O2 sensor and testing it
http://www.therangerstation.com/tech_library/O2Sensors.htm

The O2 sensor is what is setting the P1131 code but usually not the cause of the code, since your symptoms are when engine is both cold(open loop) and warm(closed loop) the O2 sensor is probably not the issue but they can go bad so worth a look