i just got a new catalytic converter and the old one was plugged, what would cause this to happen ? i was told its the o2 sensor or "many other things", what are these other things ? is there any way i can find out exactlty what caused this to happen?

 

They eventually wear out and die. If you were running super rich or super lean it would help it along to an early demise.

 

true, they just die man. from years of running the wheels off they eventually build up crap, and the o2 sensor can cause this because the car thinks its running rich or lean and that makes for some excessive build up. But **** happens and they just clog.