wow. I just got my replacement 02 sensor in; the check engine light had been coming on for months. Well, the old one was a pain to get out, it was hard to get to and I ended up having to jack the car and get it from underneath. But the car really seems to run so much better now; hope its not just wistful thinking. okay, don't know if this was thread-worthy, but no more check engine light and hopefully my gas mileage will be better than 14mpg now.
Joe

 

Did you use a generic one, or mazda? I replaced mine about 2 months ago with a bosch.. I was hoping it would break me into 20+ mpg...but no, the mileage is unchanged!! The old one was all white and nasty, too!

-Tesla

 

Is it a good idea to fork over the extra cash to get the Mazda one? Or is an aftermarket one from, say, Bosch, just as good?

 

Yeah after the 60K services, fuel injector cleaning/blueprinting, and catalytic converter replacement this would be my next suggestion for restoring power and fuel economy.

 

an o2 sensor will only effect gas millage by around 10%, so don't expect too much change. I ran without one for a few weeks and didn't notice any difference.

what code where you getting for the light?

 

Im in the 20+ mpg club. 22-25 mpg actually, depending on how I drive.

 

I got the 02 code a few month back; this last time the light came on I couldn't get a code to flash for some reason. But so far the light hasn't come back on, so thats good. additionally, the light came on when I was cruising, and if i stepped on the gas, it would immediately go out. this means it was probably the 02 sensor.
I used a Bosch universal. I wasn't about to fork over $180 of OEM
even though I hated having to cut the wire to make it work

 

my mileage used to be in the 17-18 range.
recently it plummeted to 14-16. I guess I'll see if the sensor makes a difference. Thats all I know of that was wrong; everything else is pretty fresh.

 

I'm throwing an O2 sensor in from a 91 Ford Escort, it's a 3 wire heated sensor and gives better and faster readings on the Air/fuel gauge.

 

180 bucks for a OEM !!!!! dam thats alot money victoria british sells oem for 30 bucks.


91na
intake,exhaust,S-AFC

 

on all of my 5spd RX's ive never had an O2 sensor that works, and i always get 31-33mpg, and about 28mpg if i race a lot and run hard.

 

Agent_D - Are you sure your still driving an RX-7 or have you recently bought a Honda Civic?

 

only when it's cold.... and you shouldn't be driving hard then anyways. what you want is a 2 wire one with a ground. and ground it to the same place as the air/fuel gauge. I don't think the 3 wire has a ground, but I think the 4 wire does.

 

Where are you hooking the other wires up to? Are you just finding a random switched power source under the hood?

-Tesla

 

I went to get an o2 sensor and they said that to use a non stock one I'd need to splice wires. people here are talking about 3 wire and 4 wire ones. what's going on?! could someone explain this all to me?

 

Yup just wire it to a power source. I have not done this yet but others have. It seems to work fine, plus the O2 sensor is cheaper than the Mazda one. I understood the 3 wire to be 1) power wire 2) Signal wire 3) ground wire. Am I misunderstanding something?

 

I think the 3 wire has 2 signal wires and still grounds through the sensor itself. that why there is a 4 wire one too. it has a ground. all you need is the 2 wire one and it'll be cheaper. the heated one only effects it when it's warming up.

 

there are single wire o2's (which our cars have) which ground through the metal exhaust, and the one wire goes to the ecu. by buying a non stock single wire. you just have to splice the wire together instead of paying way more for one with a clip that plugs right in.

what we are talking about is multiple wire o2 sensors. a 2 wire one grounds through the 2nd wire instead of the exhuast. so you will get better readings on an air fuel gauge. one wire goes to the ecu as normal, and the 2nd just grounds to metal somewhere.

both the 1 and 2 wire o2's heat up by the exhaust gases, and don't work correctly untill they are warm, thats why they made heated ones. the 3 and 4 wire o2 have power going to them which heat them up faster, meaning less gas use and emissions as the car is still warming up as the ecu can correct better while the car is still cold. of course the ecu for that newer car knows it's there. adding one to our cars probably would make little difference in gas and emissions while warming up.

all this means is that with a heated o2 sensor, your air fuel gauge will start to get correct readings sooner after a cold start. but like I said before. there is no way you should be driving hard while it's not warm, so it makes no point. I'd just stick to the 2 wire, it's much cheaper then a 4, easier to install. I don't think the heated one will make any usefull difference.

 

What ******* 14+, 20, 22 and 24 mpg are you talking about ?
I cannt get past the 10mpg mark

 

Dont rev the hell out of your engine and race everywhere

Im actually averaging 24-25 mpg I havent done anything yet as far as replacing anything. I dont want to jinx myself by doing it until something actually breaks.

 

You CANNOT use a 4 wire O2 sensor on the stock computer. You wil fry it. 4 wire O2 sensors use a voltage range of 0-5v. The 1 wire O2 sensors have a range of 0-1v.


Just save your money and but the Bosch. Then cut the connector off your old O2 sensor and solder that onto the Bosch lead.

 

Then go run some race gas and fry it

 

I put a BOSCH in there when i rebuilt the engine....

 

hey guys. I am new to this forum and FC.

I just got the car 2 days ago and am trying to fix the check engine light so i can have smoke check to register my car.

I figure that since the check engine light is on, it's either O2 senser or Cat. converter (the guy at service department told me so too). Well, so i went a head with a bosch O2 senser. As i install it, the engine light doesn't go away.

So my question is, after you install the O2 senser, what method do you do to flash the ECU or to reset it? I disconnect the battery on both positive and negitive side. But the check engine light is still on. Could there be something else that's going bad?

Thanks.

 

UUUmmmm..... sounds like there is something else wrong here... you should disconnect the (-) terminal and then after 5 secs step on the brake pedal. See if it still comes on.

If it doesn't, woohoo there is nothing wrong!

If it does... then turn off car, find the single green lead comming from around the front drivers side of the engine bay (by ignition coils). stick a wire in there and ground it out. then turn the key to "ON" and watch the check engin light. It should start flashing a series of code(s). Do an internet search on how to interpret flashes and their meanings... i dont know off hand .

Hope this helps and its nothing major..... probably just a loose wire connector or something... maybe TPS (throttle position sensor)