Only code? No P1151?

 

Yep, just P1131.

 

I'm stickin w/ this:
Lack of Upstream Heated Oxygen Sensor Switching - Sensor Indicates Lean -
When O2''s pooch, this is the most common type code. They get stuck in the lean switch position...(Now here's the part where you say you replaced that O2 sensor recently/ if that's the case, than something's up w/ fuel delivery specific to cylinder(s) in that bank, would be my next thought)

P1131 indicates the system is correcting RICH for an overly LEAN condition. This means the car's computer is telling the fuel pump to use more fuel (running RICH) because the engine has a low air-fuel mixture (LEAN).

The engine is Receiving too much air (metered or unmetered) or the airflow sensor (MAF) is reading inaccurately, or (O2) Heated Oxygen Sensor on that bank is worn out & has lost switching ability. Stuck on "lean".

The reason I'm leaning away from the MAF, is because that would be indicative to both bank's lean, not just "bank 1".

Wudaya think about dem apples?

 

They are too green and you should have waited longer to pick them.

 

Sounds reasonable to me. My scanner gave me the code definition the way I posted it but researching it gave the definition you posted. I'll change bank one first and if that fixes it I'll get bank two also since it can't be much better.

 

Yep. Both bank's O2's are usually changed out at the same time to optimize fuel trim. All about matched switching speeds & accuracy. Don't want dem pony's to walk w/ a limp!

But as you say, starting w/ bank 1 will test our theory.

 

I only have one O2 sensor on my 95!!!!!!

 

Your '95 F150 is OBDI.

 

If "your" truck did have another one, it would probably be located in your glove box.