O2 Sensor Test?
 

Regarding my search to end my never-ending warm start /shi**y low rpm issues:
I've heard mention on this forum of a way to test my O2 sensor to see if it needs replacing, but I haven't been able to come up with how exactly to go about this. I was just going to replace it (and still will if the forum gods suggest it) but if I can avoid blowing $140 on an already functional O2 sensor that would be nice. (btw we are talking about a 91 300TE if that changes anything). Thanks guys!
-M-

Do a search on "Ford O2 Sensor." There are instructions here that tell you how to wire an identical sensor with a different wiring connector. This way it will be cheap enough that you can just replace it.

Electrically the sensors are the same with the same output signal. It's just a matter of connecting it.

Good luck,