hi i gt a b5 series a4 with some mods to it. i gt a intake system, high flowfuel pump, boost contoller,a 3 inch high flow cat from magmaflow, and a 3 inch custom made exhaust. now about three months later after i gt the cat and exhaust done i got a check engine light. so i thought it was the cat that went bad. so i went to the mechanic and he said it was good. he says it might b the oxygen sensors. but i changed those about a year b4 i gt the cat and exhaust done. so i really need help figuring out wat to do. if the cat is not the problem then u guys think it might really b the oxygen sensors?? and if i need to replace them do i get performance ones or the stock ones? and from where should i gt them? plllllzzzzzzzi need to know cuz its drivingme craazy.

 

i think that you need to scan for the codes before jumping into conclusion.

 

i did and it said inefficient flow/ or bad cat . something like that. i went to autozone and many other mechanics dey all said the same.

 

I've heard that when people upgrade their cats or get test pipes that they trip that same code. you're running a boost controller, do you have a chip? Do you have a BOV or diverter valve? Guys running a BOV have problems with cats going bad...

 

n i dont have a chip. but im not sure if my car comes stock with a blow off valve.

 

car comes stock with a DV, its possible if your car was modded before you bought it that you have a BOV installed but.. sounds to me since you have a high flow cat that the oxys are sending a code cause you dont have a true cat converter in there.. i think the solution is that they need to be spaced out a bit? see if you can search about spacing the oxys out a bit.. when i put my test pipe in i already had a code programmed into my APR chip to not throw a code when a test pipe is installed and it prevents from throwing a code..

 

dude first off... type like **** in the gcc section, not when helping someone or asking a question, or in response to a helpful post


secondly.... you are throwing a code cause your second o2 sensor, the one behind the cat is getting too much air so it is making the car dump fuel....you need to shim the 02 sensor so it sits higher up tricking it into thinking that their is less air...



ok, now here is what you need to do... get a regular cat till you tune your car, or just tune your car... hope that whoever tunes your car can write out the 02 code and have it work for your state....lastly take the mbc off your car if you are not tuned cause it is doing nothing for your car...unless you have a map sensor and diode mod..you are going to turn that **** up too far to where you blow the turbo up