Oldsmobile/Buick Repair: I HAVE A 2000 BICK CENTRY..., spot welds, rare occassions

Question
I HAVE A 2000 BICK CENTRY THAT WHEN I STEP ON THE GAS FROM A STOP I CAN HEAR A RATTLEING NOSIC COME FORM UNDER THE CAR AND IT SOUNDS LIKE IT IS A TIME CHAIN NOSIC BUT I CHECK THAT AND IS WAS FINE I HAVE HERARD A LOT OF CARS DO THIS WHEN YOU START OUT FORM A STOP IF I SPET ON THE GAS WHEN IT IS IN PARK I DON'T HEAR THAT SOUND I CAN'T FINE WERE IT IS COMING FROM CAN IT BE THE BALFUL PLATE IN THE CONVETER MAKEING THAT KIND ON NOSIC


       THANK YOU FOR YOUR HELP TIM

Answer
usually there is a steel mesh screen surrounding the catalytic converter and over time this screen tends to break at the spot welds and causes a severe vibration. you can either have it reattached via by welding or you can use some wire to wire it tightly together where the break in the weld is at.

On rare occassions the insides of the cat stsrt to come apart, But I would first suspect the screen.