Are you sure it's running rich? Does it smell rich or is it just because you see the tailpipe is black? I don't see why the computer wouldn't notice it running rich since you just changed the oxygen sensor.

 

I cleaned the tail pipe off and it turned black again plus if you rev it the snow gets black. Also I usally get 10 to 12 mpg driving 75% hiway 25% city not going over 60 and not getting on it.

 

also I did have a lean code before I changed the o2(not now) like the pcm was riching it up. but my mpg did go up a couple since I changed it. I mean it runs well and idles good so it can't be super rich just enough to drop the mpg down 2 or 3.

 

checked fuel pressure it is about 32 running, 41 with vacuum line off , both checked at idle. left the gauge on for 1/2 hour gauge went to about 42

 

When you have the gauge on w/ engine running, shut the engine off and see how long it takes for the pressure to bleed off.

 

when i shut the truck off it sat for about 1/2 hour and went up to about 42. I also just replaced the iac valve and now it doesn't act like it wants to stall on decell at least so far.