Just did timing belt / waterpump. tensioner etc
Car sat for about a month while I pecked away at the job in my limited spare time.
Buttoned her up yesterday and when I started it, I noticed a wisp of white smoke coming from the front Upstream O2 sensor. Thought it was oil or penetrating oil overspray from breaking that ridiculous crank pulley bolt loose. So I shut it down immediately and smoke cleared. This time I just turned the key to On position but didn't start the car. Same thing. O2 sensor felt very hot right away. So it's in the keyed power supply because it doesn't do this when the key is off. If an O2 sensor fails does it do this?? How would I test this with a meter? I didn't disconnect any wires to do the timing belt service except for the ground cable on the passenger side motor mount and that was reconnected. I don't want to drop $80 on an O2 sensor if that's not the issue. NO CEL on the dash by the way.

 

I've never read where an O2 would get so hot it smokes. With the key turned to on, I believe power is sent to the O2 sensor heater circuit, so that is what could have too much resistance and heating up too high. I'd probably unplug the O2 sensor and clean the area with brake cleaner when the engine/exhaust is cold to make sure there isn't some residual fluid burning off.

 

I'll try that but the car was cold. It started as soon as the key was turned on.

 

Understood. The O2 sensor does heat up when the car isn't running and you just turn the key to the II position. Just want to eliminate the obvious by removing any buildup residue around the O2 sensor as something is burning off.

 

Embarrasingly...I simplyoverreacted The car had been sitting for about a month. It has the dreaded leaky valve covers (I have the new gaskest, it's on my list) and it was simly some accumulated oil on the exhause manifold. The way it looked it sure seemed like electrical at the time. I pulled the O2 sensor and cleaned it off with brake cleaner. Cleaned the bung as well and it cleared right up.