backtoarms

So, I have a 95 Civic with unknown miles on the engine, though I performed a compression check and it reads well. Anyway, the car came without any o2 sensors, so I figured I'd throw one on the upstream side, but I've noticed that instead of getting 300+ miles to a tank like I did when I had no o2 sensors, now I get anywhere from 110-150 miles to a tank... thoughts?

P.S. I've had the sensor on for about two months now.

NasTHatch

Take the Sensors out and get the milage back

makes enough sense

backtoarms

I mean, I get that. I was more so asking for thoughts as to why replacing my oxygen sensor (something that should increase my mileage) is decreasing it... and by THAT much.
Plus, now, I've wasted $80...

gameoverr96

how was your gas milage before?.. youre probably getting some unmetered air in somewhere and is causing the sensor to read lean so it dumps more fuel in.. its possible that you may have a exhaust leak before the sensor, a vacuum leak, maybe a leak around your intake manifold

NasTHatch

FUCKING REALLY? IT'S SAYS RIGHT IN THE FIRST FUCKING POST

Computer_Nerd

did you use a bosch 02 sensor? if so, switch to denso or ngk as an alternative and check to see if it made a difference.

backtoarms

My gas mileage was decent before; about 30-32 MPG, but now I'm getting around 11-15 MPG, which is absolutely absurd to me. I have a small exhaust leak where my catalytic converter meets my b-pipe, but that shouldn't matter since it's after the sensor; and I don't believe I have any vacuum leaks. I understand that it could be letting unmetered air in, causing it to run lean, thus dumping more fuel... but THAT much more fuel? I figured it'd be flooding my engine by now.

I did get a Bosch. Usually, I'm all about NGK or OEM on a Honda, but I figured that, at the worst, it just wouldn't help. I never thought it'd actually hurt my mileage... especially THAT badly.

Computer_Nerd

bosch o2 sensors are not recommended for civics. get a different one.

also, your air/fuel ratio is going to get crazy unless you reset the computer and allow itself to recalibrate.

backtoarms

I'm just going to pull the sensor back out. I really only changed it because idle was acting up, and figured I'd start there; needless to say, that wasn't the problem. Just wish I could get my money back for the sensor.

Fabrik8

So you're getting an O2 sensor fault when the sensor is missing, correct?