I just got an evo 8 mr. got it from the dealer and there was no cat on it so i believe the guy tuned, ran the car without at car. so i order for me to pass the e test the cat was put back on. i took the cat off again but left the o2 sensor on. so i was wondering if it's a good idea to leave the o2 sensor there or take it off. of course the check engine light will come on again but that's no biggie. got an invidia down pipe and test pipe as well.

thank guys.

 

I just got an evo 8 mr. got it from the dealer and there was no cat on it so i believe the guy got the car tuned without the cat. so in order for me to pass the e test the cat was put back on. i took the cat off again but left the o2 sensor on. so i was wondering if it's a good idea to leave the o2 sensor there or take it off. of course the check engine light will come on again but that's no biggie. got an invidia down pipe and test pipe as well.

thank guys.

 

you can buy a spacer from just about anywhere to pull the O2 out of the exhaust stream. i know AMS has it on their website but you can use spark plug defoulers as well.

i just drilled a small hole in my testpipe and welded a piece of 1" tube to cover the hole, and welded a bung onto the end of the 1" dia pipe. you can also buy test pipes with this type of O2 bung on them already.

not sure what emissions are like in the great white north but if they are anything like what they are in the chicago area i just passed emissions with no cat with that setup.

 

thank man but i'm just wondering if it will mess up my ecu if i leave the factory O2 sensor on there. there's a spot on the test pipe for the o2 sensor and i have it there right now just need to do if it's a good idea to leave it or remove it.

 

You can leave the O2 on there, it will not mess up your ecu. The rear O2 is use for monitoring the Cat.

 

thank that's the only thing i was worry about.

 

I installed the spark plug defouler in order to get rid of a code for cat converter, but now I'm getting p1157 code. Any connection?

 

P1157 is NOT an active trouble code related to a Mitsubishi Evo's ecu or any Mitsubishi for that matter. Honda, Ford, Acura, Audi, BMW, VW, Mazda, and all GM vehicles could display this code but not a Mitsubishi. They don't have a HO2S22 switch....the code itself relates to a lean condition. The rear o2 sensor as previously stated in this thread is only there for cat monitoring. It has a heater circuit and it reads whether or not the cat is working efficiently. That's why ppl remove them all the time. Closed loop fueling is a function of the front o2 senser.