i was about to take off my exhaust a minute ago, but i saw some kind of sensor and want to find out what it is first. it's on the passenger side pipe, about a foot down it. it's some wire that goes into a metal tube that's bolted into the exhaust pipe. i'd just like to know what this is and what it does before i take off the exhaust

 

Oxygen sensor... Snifs the air/fuel ratio from exhaust. Very important, just take it out and when you install your headers put a new one in, those things should be changed every 5 years or so. Nobody ever does though.

 

i'm not puttin in new headers, just new pipes. the o2 sensor, unless i looked at it wrong, is just screwed into the exhaust pipe not the header, so i guess i'll just drill it into the new pipes

 

why is it important for the engine to know the air/fuel mixture that's leaving the car? what does it do with the info?

 

If there's excesive fuel in your exhaust, the computer gives your engine less fuel, more lean mix. And if your engine is running too lean, it gives it more fuel, more rich mix. Im not sure how will your engine run in closed loop if you dont have the sensor at all, never tried, but im thinking it wont run good... Oh and its the only way the computer knows if the mix is rich or lean, from the exhaust fumes.

 

be careful, the threads on it are very eaisly stripped, you
don't want to lose any of that stuff in your exhaust system.

you need to put some anti-sieze stuff on the threads if you
reuse that one, but it's not adviseable, i'd just replace it.
once you put it in once, you can't take it out and put it
back without the anti-sieze goop, them suckers weld themselves
in there like rust on a 1950 ford pickup


if that makes any sense...

a new one is like, $14 at autozone.. something like that..
not too expensive..

oh, and your engine will run like total **** with no O2 sensor,
not to mention the constant SES light, and the car won't
go into closed loop, so it won't advance timing, it'll use
hard coded timing maps. and it'll burn a TON of fuel.

my 91 Camaro Z28 convertible (305 TPI) got 6-8MPG when the TPS
and O2 sensors died.