driving with rear o2 sensor out of range!

jason5151 · Post by **jason5151** » November 27th, 2007, 2:33 am

im currently driving with my rear o2 sensor throwing a engine check light,
my mechanic says that it will burn a little rich meaning it will give the engine more horsepower but i will lose a little in fuel economy and not bad for the engine.
is this true?? or not? and if its true isnt this one way to increase power without spending money!! just a thought what if 2 o2 sensors were gone,based on his statements this may also yield more hp at the cost of fuel efficiency.. i currently get around 500 km per tank on my 1.8!

hgallegos915 · Post by **hgallegos915** » November 27th, 2007, 3:40 am

it wont give the car more horsepower.. theres a chance the car will go into limo mode and lose alot of power. Im not to sure if the o2 sensors cause limp mode.. i do know the knock sensor does..

Vanished · Post by **Vanished** » November 27th, 2007, 6:44 pm

o2's cause limp.

The only other complication is if your burning rich you'll cook your cat converter, so just get a new one off ebay, fairly inexpensive and easy to change.

jason5151 · Post by **jason5151** » November 28th, 2007, 4:30 am

but it is only one that is out of spec..the first o2 sensor is to make sure the car is running clean the second only double checks the first reading,correct me if im wrong here but this is how it was explained to me ..
i feel no loss in power with the 2nd sensor gone but it bothers me to see the engine light on...
any ways im getting it fixed for 300.00 cad!!

umcamara · Post by **umcamara** » November 28th, 2007, 4:36 am

You could save over $200 by doing it yourself. VERY easy to do if you have a wrench and know how to turn it.

hharb · Post by **hharb** » November 28th, 2007, 11:30 am

dont even need to do that.. just get a ebay o2 sensor instead of a mazda one, and u save a good $100 right there..

jason5151 · Post by **jason5151** » November 28th, 2007, 12:25 pm

oh ya that easy,what about the wiring?
i would do this myself but what if it breaks in the threads when i take it out?
and say it comes out easily reseting the engine light is as follows..
disconnect + terminal then hold downbrake for about 30 seconds and that should do it huh!

lowflyinmx3 · Post by **lowflyinmx3** » November 28th, 2007, 12:34 pm

Do it yourself. It doesn't take that long. I got mine out and in 15 mins. Althought some are tough to get out, definitely worth it to try yourself first.

fieromx3 · Post by **fieromx3** » November 28th, 2007, 5:14 pm

ur mechanics scrwed.. theres 2 sensors cuz its a V6... one reads the front bank trhe other reads the rear bank thats all there is to it lol and running rich makes u lose power.. are cars run rich as it is and dumpin more fuel into it only makes it worse.. get a new mechanic

mx3autozam · Post by **mx3autozam** » November 28th, 2007, 5:36 pm

fieromx3 wrote:ur mechanics scrwed.. theres 2 sensors cuz its a V6... one reads the front bank trhe other reads the rear bank thats all there is to it lol and running rich makes u lose power.. are cars run rich as it is and dumpin more fuel into it only makes it worse.. get a new mechanic

Actually his car has 3. and when he says one is to keep it running clean and the other is to double check. His car is a 96 so it will be obd2 therefore there will be one more sensor after the cat that will double check. If that one is bad it won't cause any issues as long as the 2 precat ones on each bank are working the way they should. Running rich will kill economy but definitly not gain anthing. It is time for a new mechanic.

fieromx3 · Post by **fieromx3** » November 28th, 2007, 7:26 pm

i dint see it was a 96' lol

jason5151 · Post by **jason5151** » December 19th, 2007, 1:20 am

new o2 is installed! with much more power,and car sounds better!well it better for $250.00 sensor! just cant wait till the others let go!lol!

RS_OBD'oh_2 · Post by **RS_OBD'oh_2** » December 19th, 2007, 8:53 am

That's sweet that you are up and running.

Regarding the secondary O2 sensor... I thought that it was checking the performance of the cat. I've been told that the ecu needs to see a difference in O2 sensor readings b4 and after the cat. Therefore, the ecu will either richen or lean the mixture based on the secondary O2 readings. I could be way off here.. This is just what I have been told. Please correct me if I am wrong.