Crazy O2 Sensor

When I first bought my civic, 88 DX, the oxygen sensor was busted off at the manifold. I drove it for years like this, and finally decided to replace it. I put one on it, and wired it up, and when I hook it up, i get worse gas mileage. I thought an O2 sensor helped mileage? I usually drive with it unhooked now for obvious reasons. But can anyone explain this?

wtf? that seriously should not happen...i dont know what to say.

My O2 sensor has been bad since I bought my car (7 years ago), and it has never effected my gas mileage. I even replaced it with a POS Bosch...still had the same problem (code 1 on the ecu), and my mileage was never effected... I just ran rich - unless I paid attention to the a/f ratio gauge. With the gauge I was able to keep the car runnin' 'stoic', so I wouldn't trip the ecu...

yes, i had the same problem, i replaced the o2 sensor, and the code 1 didn't show up instantly, but did after 30 mins or so of driving. maybe it's defective, i dunno.

I tried replacing the O2 sensor with a Bosch (which, apparently, suck). The problem never went away. But since it wasn't really effecting anything I just dealt with it.

I didn't want to spend the $$ on an O2 sensor from the dealership...

Mine did it mostly when it was hot out. I don't remember ever having a problem when the weather was cool....

Ive been running a bosch O2 from autozone for over a year now and not only did it fix my CEL and erratic idle but i get greater mpg and i dont run as rich...and im still missing a cat.