Why does my catalytic converter keep on breaking? When I first had it replaced, I heard this awful vibration sound at around 2000 RPMs and I knew it had something to do with the resonance inside the exhaust system. So I took it to a muffler place (cheap one) and he raised my car and shook things around and pinpointed my cat to be the culprit. That was about 1.5 months ago and now my cat seems to be doing the same thing again. Should I just get a high-flow cat or something? Help! Thanks!

 

If it is a rattling sound, it is your heat shield. Just remove it and you will be fine or you can just go buy a highflow cat

 

my cat lasted for 60,000 miles, they aren't cheap either!(quality one)

98 4cyl