Code 173 - (R,M) Oxygen sensor not switching - system is or was rich - Single, Right or Rear HO2S - Fuel control

[myotis1134]

First drive of the day, warmed it up for a good 10 minutes. Code popped up when i hit the highway.

Ford OBD I website lists it as:

(R,M) Oxygen sensor not switching - system is or was rich - Single, Right or Rear HO2S - Fuel control

Swapped out the O2 sensors about 3 weeks ago, the fuel pump a week before that. Switched the injectors from +2 lbs back to stock, and installed new pulse damper and pressure regulator on the rail - about 2 months ago. Have not recently changed the fuel filter, but how would that cause a rich code?

Admittedly my throttle response is not where I expect it to be after putting in a basically new fuel system. I'm going to check my air filter right now. Air filter looks damn good after a year! Fram air hog.

CCRM was replaced last year when I was trying to run 48 lb injectors, but I'm wondering about my barometric pressure sensor - if that thing was off even a little, your mix would be way screwed up. Any chance this could be causing me to run rich?

 

[rubydist]

iirc, the fuel trims can get to 120% or 80% before they throw the code. The barometric pressure sensor would have to be off a ton to get to that point - that's the equivalent to about 8000' feet of elevation error.

I wonder if you have a bad injector that does not want to turn off. Of course its on the rear bank, but I would pull plugs and check what they look like.