Thread: Rattling noise please help

does it smell like rotten eggs? good sign of cat being clogged. Also if u dont already have an automotive stethascope, take a piece of hose, like heater hose, put one end to your ear and put the other end to where the coupler is and if uhear the sound in your ear, wahla. or take your s/c belt off and start the car, if no sound with belt on then its 9 times out of 10 your coupler.