90' Bronco ii losing power/bad mpg

[A4LD_Nghtme]

My Bii was running great up until about a month ago when I got a code 41 CEL. That code has since gone away after a good ol italian tune up and has not returned in the past 3 weeks. However, I now notice that when I hit the gas after being stopped it feels incredibly weak even if i floor it. If I'm moving and hit the gas, it will downshift and I get the revs I expect then but not from a stop. What could be causing this? Im also losing power up hills(I live near tahoe in Twin bridges) in 3rd gear and need to ride 2nd gear. I'm going to recheck fuel pressure tomorrow because it came back normal last I checked a few weeks ago and this is including the disconnecting of the fpr check. Fuel filter is 2 weeks old. The sparks are 2 months old. The FPR seems to test fine during pressure test. Also, I'm getting terrible mileage(about 330 miles per tank). No codes KOEO or KOER

 

[rusty ol ranger]

Hows it run cold?

 

[RonD]

+1 ^^^

41 (R) System lean – Fuel control
(M) System was lean for 15 seconds or more (no HO2S switching) – Fuel control

Check the Fuel Pressure Regulators Vacuum hose for gasoline, shouldn't be any of course, yes that should cause Rich code, check it anyway, lol


O2 sensors are THE ONLY sensors that wear out, 12 years or 100k miles, which ever comes first
They use a chemical to detect Oxygen in the exhaust and it simply gets Used up
O2s make their own voltage
0.1v high oxygen, lean
0.9v low oxygen, rich

As they run out of chemicals the voltage goes down, so FALSE lean, which causes engine to run Rich and sluggish and MPG goes down
If you don't know the age of the O2 change it

Then drive it for a week or so, computer needs to relearn fuel trims for new O2