Thread: Catalytic rattling?

Does or can a catalytic converter rattle when it's going bad? It sounds like a loose heat shield and only happens under light acceleration up to 2k rpm's. I can't find anything loose under the car. The car isn't suffering from any of the usual performance issues when a cat goes bad and there aren't any check engine lights except for a recent P0455 large evap leak. The rattling has been happening for a while.

it could, get under the car and bang on the cat to see if you hear it rattle.

It does sound like there is a rattle coming from the cat when I bang on the exhaust. It won't be a problem if it rattles as long as it doesn't throw a code, right?

its gonna clog up on ya one day. so id plan to replace it.

Is there a particular cat I should get?

Likely there's a shield on the cat.. they like to come loose. Take a look and if it's the shield, clamp it or weld it.

theres no shield on the cat, its in the tunnel. it can come loose and rattle.


what brand depends on your year, 01 up you want a stock replacement, older you can get a hi flow with no issues. 01 up a hi flow cause over fueling and cat codes.

There might be

I'ts for my '05 GP. I took the tunnel shield off last year because it was about to fall off. I'll look again for a cat shield but I don't remember seeing one. Thanks for the info.

dont think the 04-5 have the cat test over fueling issue, i think you could get a cheap hi flow cat installed. or a zzp catted dp or a zzp off road dp and install a cat in it. if you change the dp, may as well get the 3 inch.

Some do, some don't. You're best off with a stock replacement.

Well, I found out what the rattling was. The flex pipe just bit it. I have a full cut out now. lol

Are any of these cats any good? I was leaning toward the Eastern cat.
2005 PONTIAC GRAND PRIX 3.8L V6 Supercharged Catalytic Converter | RockAuto

rev it up and see what happens

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Replaced the cat and all is good. No more rattle. What do I do with the old one? Trash or does it need to be recycled somehow?

take the cat to a recycle scrap yard, you'll get about $40 for it.

my scrap yard offered just the weight. seems these cats are not wanted as much as the diamond shaped cats from the 80's.

I'll put it in the pile of rotors and take it all at the same time.

now rotors add up, thats #1 steel. id be scrapping my own pile of rotors. thing is you need a pile to make it worth the trip.

id tell hey i got a cat...what they worth these days? seems its hit or miss these days from yard to yard.