an o2 sensor sends inputs to the computer, the computer determines these inputs thru voltage, an 02 sensor should send as a good 02 sensor, 200-900mV (200 being lean/900 rich) it fluctuates to keep a 14.5:1 a/f ratio, if your 02 sensor is falty its either going to tell the computer its running rich or lean all the time, if it tells the computer your running lean its going to send more fuel, this could be caused by a hole in the exhaust, vacuum leak...but it could also be a bad maf, it could be an open egr valve it could be many things, go to a dealership and ask them to check it out, there are so many things that could cause a bad gas "crisis"

 

i'm living on ramen noodles right now. how much would an o2 sensor run? I also got a torn cv boot on mypassenger side tierod. you kow how much they are and how big a pain they are to replace?

 

I was getting terrible gas mileage, changed out my O2 and now I average 27 with mostly highway miles and a slightly heavy foot.

 

Some 30 something bucks for a new OEM sensor.

 

yeah, gas is becoming a killer. Im getting about 15cty 20hwy in the 8, 240 is getting bout 25cty 30hwy though. Pistons still dont make me smile like rotors can, but damn I sure dont cry as much at the gas station with em.

 

that 8 is a nifty ride. so's the 92 notchback. i just know it's capable of a lot more and im vexed to figure out why. I can make a 40 mile trip one way,(highway), and it'll drop from full to almost 3/4.

 

ive been getting 20-24mpg since ive owned my car and you guys are honestly saying that is bad gas mileage? i only get 15-17 mpg in my 4cyl. s-10 pickup so i thought the gas mileage in the 240 was good. how hard is it, what is involved in installing an o2 sensor?

 

the o2 sensor is located below the heat shield in the engine bay on the header right?

 

Disconnect sensor, unscrew it, take it out. Screw new sensor in, reconnect, done.

 

ahh, i see said the blind man.

yay im a fruit with 100 posts!

 

Not bad suggestions, we should have a faq and sticky reguarding 02 sensors and gas mileage...I'm gonna do mine this weekend! I can't tell if my mileage sucks due to my heavy foot or the 02 sensor...lol.

 

I got 400 miles on one gas tank once I just reset my ECU and am running 91 octane now. ECU got everythign straight, got 24.5 mpg

 

I got 36 MPG on my last trip and that was through the mountains of west virginia. Of course i have upgraded the car. I got an RB20DET. You guys might try cleaning the MAF sensor also and cleaning the throttle body. when i had the stock motor that helped to improve my gas mileage.

 

What year is your 240 dmytry_arnason? I have a '92 and according to edmunds.com, brand new the gas mileage was rated at 22mpg/city and 27mph/highway. I am thinking I am getting around 20mpg but I haven't quite calculated it up, and I drive it hard all the time soooo... In any event, put some Gumout Fuel Injector Cleaner in, check your spark plugs and plug gap, check your airfilter, and cap and rotor button on the distributor. Also u might try changing your fuel filter if it has a lot of miles on it. I'd say if it even has 40,000 miles you might go ahead and change the fuel filter anyway. Also, what kind of wheels are on it? Bigger rims mean more weight which also hurt gas mileage. Also, if your 02 sensor is bad it will show up on a ecu scan tool. Good luck with it.

 

also make sure tire pressure is good. i have mine at 32psi (cold)