Paulcomi

Recently I replaced both my catalytic converter‘s and I suspect that hi I had a small exhaust leak at the manifold connection. Anyway today I loosen everything up and reconnected it all and I believe I fixed it but I noticed when I started up and ran it that there was some smoke billowing up from the manifold area so I climbed under the car with it running and was able to confirm that my O2 sensor after the cat was smoking. Also the body of the O2 sensor looked blackish. My question is other than maybe oily hands getting on my exhaust and burning off is there anything else that would make an O2 sensor smoke?

190Efan

Unless there's an oil leak elsewhere that's now dripping on your O2 sensor is maybe a possibility? You might try buying some engine dye at your local parts store and running that in your car to see if you can identify any other oil leaks.