Actually the cat matrix could have collapsed OR a baffle in the muffler could have come loose - either would block the system and give your symptoms - while the car is running check for exhaust flow while a friend gooses the throttle - compare to a similar vehicle idling nearby -
Another thought is a bad ignition advance - (you can check that one with a timing light) - or - a wiped cam shaft that's not allowing the exhaust valves to open all the way (in other words, the lobes are damaged) -
Steve
|