when i turn on my car, and when i take off in 1st gear, there is a loud rattling sound underneath my car. i recently bought my prelude used, and the previous owner had put some bolt on exhaust on there, which makes me think that is where the sound is coming from...anyone else have any ideas? because i put it up today and couldnt really find any loose parts

 

Maybe there are pieces of metal in your cat. My car currently has this problem.

 

theres a exhaust bracket under there i think its bolted onto the motor somewhere i had this problem that bracket broke and its ratteling. Just a suggestion

 

yeah i took off the heat cover and shook the cat...and it still rattled...whats the best way to get the crap out??

 

take it off and dump it out

 

your cat is probably bad, look into replacing that

 

there isnt foreign stuff in your cat, its the honeycomb stuff inside of it went bad, it deteriorated and now is rattling inside of it

 

is there any welding involved when replacing it??

 

Will taking the cat off and dumping it out set off a check engine light once it is put back on?