When an 02 sensor fails...

[frapjap]

When an 02 sensor fails, does it have the possability to fail on the lean side? Heres my scenerio- I'm pulling codes for a misfire, and lean. Now, I just reaplaced plugs and wires because of a NASTY miss (there was a dead cylinder) and all runs well up til about 5 minutes or more of driving. The miss comes back ever so slightly under part throttle at cruise of 20-40moh. Now, my cats have also been tested and one pressure tests good, one is not so good, so they're getting replaced. But, the more I think about it, I wonder if the 02 sensor has finally taken a dump and is causing a lean condition vs. the usual over compensation of rich. Is this possible? Am I crazy?

[elwesso]

its possible that if its kinda failed it might do that, but if it failes to the point of a CEL the computer has programmed values for cruising... since all of your cars are OBDI, none of them are going to use the o2 sensor except at cruise.. Not very often to o2 sensors cause driveability issues.

[frapjap]

its possible that if its kinda failed it might do that, but if it failes to the point of a CEL the computer has programmed values for cruising... since all of your cars are OBDI, none of them are going to use the o2 sensor except at cruise.. Not very often to o2 sensors cause driveability issues.

Ah, I failed to mention its in a Ford Windstar. Its a 1998, so its OBDII. It seems odd that I only get my miss at cruise and never under acceleration. It seems right that way because its getting fuel under throttle, but if the 02 is telling the ecu to lean out at cruise, then I could understand my miss. Buuuuut, I'm really not sure if my thinking is logical.