Is this noise my catalytic converter self destructing?

Mike Puckett

SCCoA Member
It's the original and it sounds like somebody shaking a rock inside a big coffee can. It's worse at idle, goes away when I increase the rpm, does it when the car coasts or is accelerating and goes away at constant speed. And Oh it did it going over a real bumpy road. It's been doing it for about a week now. I was even wondering if we dropped an nut or washer into the downtube while it was opened up when we put the motor in. Under the car I can't tell whether it's the transmission or the cat but my transmission guy says there isn't anything in the AOD that will sound and act like that. I did notice a decrease in power once when I accelerated hard. Could it be that as it disintegrates it's plugging itself up? Anybody had these symptoms who could verify my suspicions?
 
Last edited:
if you have stock wheels, take off the covers and see that no stud broke off, mines did and i thought it was the cats and it turns out it was a broken stud. exactly the same sympton as urs!
 
I just went and checked the wheel studs on the left front wheel and they're Ok. The exhaust sounds a bit motorboaty and it has no acceleration but drives normally otherwise. It's got to be that left side cat.
 
yeah, i had that same sound...

and it was the cat on the driver side... so i had catless downtubes made...sweet, smells bad sounds bad, but non restrictive:cool:

put it on some ramps, and hit it with a rubber mallot...see if it rattles.
 
id get that cat fixed asap, my cat was rattling for a few days so I bought the new cat and as I was awaiting its arrival in the mail my hgs blew because of all the back pressure
 
I just went and checked the wheel studs on the left front wheel and they're Ok. The exhaust sounds a bit motorboaty and it has no acceleration but drives normally otherwise. It's got to be that left side cat.

Mike sounds like the sheild on the cat is loose or the material inside the converter is breaking up...and yes it can clog itself when it starts breaking apart. The high flow cats I had contained two stages of the ceramic honeycomb looking stuff. I had a nitrous backfire that shattered the first stage and that clogged the 2nd stage. Exhaust was muffled, down on power and the o2 sensor on that side was showing to be very rich when it really wasn't. Made the motor feel like it had a slight miss too.

David
 
I checked the shield and it's been removed. Sounds like it is coming apart inside and it is definitely down on power. This is a new motor so I want to get it fixed right away.
 
It was the right side cat. Noises sure can be deceiving. I had the old ones from my drag car put on it. They were only 5 years & 50,000mi old. And indeed, a broken piece would roll right up and almost completely block the outlet pipe. Runs like a new one again.
 
I had that noise come up on me once on may way into work, just out of the blue. Then after one red light turned green and I accelerated a bit fast I heard a thunk, and the motor lost power immediately. I limped to a parking lot and looked under the car. The passenger side cat was RED HOT. I let it cool then hit it and heard a chunk rattle. Turned out a chunk stuck in the outlet of the cat and effectively plugged the exhaust.

Didn't blow the head gasket, but you know that isn't good for a car.
 
I had that noise come up on me once on may way into work, just out of the blue. Then after one red light turned green and I accelerated a bit fast I heard a thunk, and the motor lost power immediately. I limped to a parking lot and looked under the car. The passenger side cat was RED HOT. I let it cool then hit it and heard a chunk rattle. Turned out a chunk stuck in the outlet of the cat and effectively plugged the exhaust.

Didn't blow the head gasket, but you know that isn't good for a car.

i have the same problem .... i dont know if i can remove it and replace buy normal piping .. >???
 
i have the same problem .... i dont know if i can remove it and replace buy normal piping .. >???

At the time I was broke, so I cut the tube off at the back of the cat. I then removed the down tube with the cat attached and cut that off. The stub that was left was pretty small, but I then got a piece of flexible exhaust tubing and clamped it to the down tube, attached that back to the manifold, and then slipped it over the remaining exhaust pipe and clamped it on there.

It was a joke of a fit, but it did work for a while, just leaked and was a little noisy. The following summer I cut the down tubes off and attached some new down tubes - eliminating the cats.
 
remember to clean out the resonater and or mufflers it travels down and clogs them up too those damn catastrophic perverters
 
Back
Top