More than likely, it is. When the O2 sensor goes, typically, your computer will default to a richer than normal mixture to prevent damage to the engine from a mixture that may be too lean. As a result, you'll get a rotten egg smell as the richer exhaust passes through the catalytic converter.
[updated:LAST EDITED ON 19-Nov-02 AT 10:12 AM (EST)]They do get plugged, but also can go "bad" as it can no longer perform properly and a rotten egg smell is one of the first signs. A bad O2 sensor can cause a funky smell, but that is from the sensor causing the engine to run rich. The smell will be more fuel like(for lack of a better work)
Exhaust never smells good. But rotten egg sulfur smell has to be killer. Hope you have a strong stomach until you get it fixed. if it is Cat get a Bassani high flow cat to replace it since you are going to have to replace it.
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