I recently put a heated o2 sensor in my car. Since then my Holley adjustable regulator went south (like many others!) and was leaking fuel into the manifold. The vacuum connection is closest to the cylinder that happens to be right above my o2 sensor on the headers. Now that I have replace my regulator I cant seem to get the BLM's back in order. It's always lean even when I've lowered my injector constant by as much as 2.5#'s. And the readings are strangely low and many times 0. And a couple of times I got a "lean o2" code. Not all the time though.

I had also in this time frame cleaned my throttle body on the car with a supposedly safe for o2 sensors cleaner. I ended up with some of the cleaner puddleing up in the plenum.

Could running rich have fouled my o2 sensor? Has anyone had problems with TB cleaner affecting their o2 sensor?

 

Yes running rich can foul an o2 sensor. That sounds like thats what happened.
O2 sensors will always fail lean. If they are constantly all the way lean you know their bad.

 

Running rich over a long time will do damage to the o2 sensor.. it may burn away or not... but there is a big chance that the o2 sensor goes bad (mine did that before...)