My V6 started throwing error codes once warmed up: right bank lean trim differs too much left-right Engine seems to run okay though. So I checked out usual stuff. I found all the right side spark plugs are sooty, and the left side spark plugs have nice brown deposit. So I suspect the right exhaust oxygen sensor is crying "too lean" and the PCM is pumping too much fuel into right side. The sensors were probably never changed (it was a few years old when I bought it). There exists an error code meaning "no exhaust sensor" but that is not flagged. Is old exhaust sensor the common cause of this problem?
Also wondering, if there is unburnt fuel, will it wash oil away and cause accelerated wear?