I believe there are two 02 sensor's. There is one 02 sensor on the exhaust manifold, and then there is another 02 sensor on the cat/midpipe. Correct? Do you absolutely need both of these 02 sensors. I know it "runs" without both of them, but does it harm it, or make it perform any different without both 02 sensor's?

Ohh BTW, it's a '91 240sx KA24DE.


Right now I don't have any 02 sensor's. There is one in the exhaust manifold, but it isn't hooked up, it's blocking the hole though. The 02 sensor for the midpipe isn't there. There is just a hole. I just swapped out engines at home. My car isn't really running right. I'm trying to pick at the little problems, to get it running perfect.


Thanks,
-Jeremy.