one missing O2 sensor.

It is best to replace both in pairs, but folks replace one (and leave the old one on the other side) all the time.

Good luck.
 
You could find them much cheaper by getting a hold of Randy Stinchcomb either here or at Modular Depot.

The front ones measure the air/fuel ratio in your exhaust, and send signals back to the PCM to tell it to adjust by going lean/rich.

The rear ones (can't remember if foxbody's have them but SN-95's do,) monitor the efficiency of the catalyst system, and report it back to the PCM in form of certain voltage.. (yes it's working, or no it's not.)
 
Andy is kinda thinking of his nice '04. Foxes only have two O2's (4 O2's are for OBD-II cars with the catalyst monitoring, like he said).

Autozone should have Bosch O2's for around 40 bucks each. And some guys get theirs from a site similar to
oxygensensors.com (not sure if that is exactly correct).

You really could be alright just doing one, so long as the other one still works halfway decently (what happened to the bad one?).

Just like Andy said, they just relate exhaust info to the puter so the air fuel ratio can be trimmed.
 
HISSIN50 said:
(what happened to the bad one?).

I snapped it off accidentely when I was installing my Tremec.:doh: Was in a hurry to try the new tranny out. Parts store was closed so I said I'll get to it in the winter time.

It's been bugging me for the past 3 months now. Car did run fine without it.
 
TrophyHead said:
I snapped it off accidentely when I was installing my Tremec.:doh: Was in a hurry to try the new tranny out. Parts store was closed so I said I'll get to it in the winter time.

It's been bugging me for the past 3 months now. Car did run fine without it.
I gotcha. I thought it might have failed for some reason, in which case the other one might not be far behind. You should be able to just replace one (you can always swap in the other one at a later time if you want).

It is funny - they do run pretty decent with no O2's. The slight increase in fuel economy is kinda nice though.

Good luck.