All o2 sensors codes tripping

Question

Recently rebuilt top half of my v6 Xterra. Ran great at first. After a week or so it tripped an O2 code. Cleared it. Next time both bank 1 o2 sensors had tripped. Just tonight I checked again and had nearly all O2 codes tripped (10 in total) and a bank 1 knock sensor. Now there is a noticeable miss when idling. Want to save this engine. Followed all torque specs and used new gaskets in rebuild.      Side note....  A few times after rebuild I noticed a large amount of water coming out of the exhaust tailpipe. Wasn't coolant or fuel. Was still running good at this time.

Answer 1

The oxygen sensor is just responding to the engine mechanical condition, Until the cause of the engine misfire is found,  you would need to rule out a mechanical condition by doing a compression test, or better a leak down test,