(Downstream on left, upstream on right has been cleaned up already)
On a long drive in my wife’s 2003 Altima 2.5, the car started bogging way down. I had just fixed a misfire that had been caused by a leaky valve cover allowing oil into the spark plug tube for cyl 2, but the car had been driven with the misfire for a WHILE before I could get down there to fix it, and I guess the whole time it was just dumping fuel into the catalytic converter. Even the previous owner who we got it from four months ago was driving it around like that.
Well, I pulled it over in some small podunk town, and pulled the upstream O2 sensor, thinking I’d let the motor have some outlet to exhale. The sensor on the right is the upstream, cleaned up. When I pulled it out it had carbon deposits just like the one on the left, just no soot on the bottom. I also noticed a small crack in the pre-cat just below the point where the exhaust manifold joins the cat, telling me that the exhaust leak I had been smelling prior to all this was probably right here.
Anyway, will gutting the precat and reinstalling it be my best bet? And how in the name of God did my upstream O2 sensor get blown out so bad? Thanks.