I seem to have a bad front O2 sensor...slow to heatup and slow switching. My question is what are the possible ways that an O2 could be damaged? The reason I ask is that this O2 is relatively new...yeah, small chance I got a "bad" new one from GM...doubt it though.

But what could damaged O2s? I heard the ceramic coating from new headers could damage them. What about WD40 if used to remove them from the manifolds? Anything else?

 

bad fuel?

additives?

 

Running rich, especially if you have an exhaust leak...if I am not mistaken.

 

Lead from leaded fuel, silicone from RTV and non Dex-Cool coolant, applying anti-sieze to the threads (sensor comes with correct amount of electrically conductive anti-sieze already applied), anything that seeps into the "air" passage on the outside of the housing - WD40 would certainly qualify. The sensor works by exposing the inside surface of a zirconium thimble to the exhaust, and the outside surface of the thimble to "air" as a reference..... and the air needs to get through the same hole on the end of the sensor as the wires.