Ok i just spent last night installing a Y cutout on my exhaust i haven't put the main exhaust back together and i took it for a spin. Check engine right away, i let it warm up restarted and more of the same. I welded the bung right before the y thinking my o2 would still be happy. so as my car sits it has open down pipe at a Y (open at both exits). if there is a thread about this already then just post the link please. i tried a search btw
thanks all

 

maybe o2 sensor isnt able to read the exhaust? Check the code.

 

bump

 

m3 why would that be? have you heard of that happening before??

 

I am running open DP, and my 02 sensor is in the stock location. . no CEL.

 

what year's your car? If it's obd2, it'll probably throw a code from not reading exhaust flow after the cat wince you're cutting it out...just a thought.

If this is the case, get an o2simulator.

 

95 obd1

 

when is it throwing the code? what is the code?

 

don't think he checked the code it goes away as soon as the car is shut off...the just about stock location. CEL only comes on sometimes after boosting hard.