After driving my car for a while and turning it off within any time between 2 to 10 minutes later i hear an extremely loud bang come from under neath the car. ive been pulling the code for my cat for about a year now but never got it fixed because my mechanic said not to worry until i needed the car inspected.

what the hell could the banging noise be and what does that mean? im assuming it has something to do with the cat...

 

if the car is off, the only thing it could possibly be is an exhaust component making noise as it cools and contracts....if there is already suspicion on the cat, I would replace it first and go from there...

 

I had a 90 Saab 9000S a while ago and when my cat got plugged up it turned red hot and made a banging noise when it started to cool off. I eventually had to replace it.

 

back fire?
EVAP problem?

 

yeah thats what i figured. can the car get damaged by that?