Hey all i had my cat replaced on the car few months ago, since then i can hear a hissing type noise when accelerating next to buildings. I thought it was just a leak in the exhuast (dodgy welding). Took car back they couldnt find any leaks so they thought it could be a dodgy cat or muffler.
Whats worrying me is could it be my cat blocking up again? I extracted fault codes seems that i got a code 133, Upstream Heated Oxygen Sensor circuit Slow Response - Bank No. 1. So does this mean my oxygen sensor is stuffed, and causing my CAT is block up again???
I checked my plugs today, on the tips they are grey, which means the car is leaning out. I think my car is down on power as well.
so do these symtoms relate to a stuffed oxygen sensor?