i have a 92 civic si and at low rpms i have the rattle that seems to be coming from my cat but when i jacked up my car and held the cat and started the car the cat was not rattling any one have any idea what it could be? the problem is very annoying when im driving down the street and i hear it rattle thanks in advance for the help

 

Had that problem with my 4 door Integra recently. It turned out to be the shield around my cat.

 

It's either the heat shields or the springs attaching your cat to your exhaust manifold or the gasket between the exhaust manifold and cat.

 

get under the car... start shaking the system in different parts to see if its just hitting the heat sheild... if it is thats an easy fix, just bend the heatsheild out of the way....

if that doesnt solve it, make sure all the bolts are tight where the flanges connect different piping.

if none of those are it, then most likey its your cat. push the cat down from the top of it and bang on it with your other hand hitting the bottom of the cat... if you hear something then bingo...

the car need not be on to do the above "tests"

 

heatshield or the rubber pieces are worn out, so the exhaust bounces against the chassis

try to shake the exhaust system, or try to locate it while the engine is running

 

ill will try all these and hopefully it will work thanks alot