Thread: Catalytic rattling?

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  1. #1 Catalytic rattling? 
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    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.
    '97 Grand Prix GT Coupe
    '05 Grand Prix GTP Sport Red Metalic SOLD
    '05 Grand Prix GTP Silver
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  2. #2 Re: Catalytic rattling? 
    Killa Bee Scottydoggs's Avatar
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    it could, get under the car and bang on the cat to see if you hear it rattle.

    98 Buick Regal GS, F body brakes, Caddy STS wheels, tinted tails L36 bottom end, lightly ported heads, 1.95 roller rockers, headers, gen 5 N* 3.0 pulley, FSIC, 42 lb injectors, a BrandonHall rebuilt trans, DHP tuned and AEM water/Meth injection https://goo.gl/gpV5kW
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  3. #3 Re: Catalytic rattling? 
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    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?
    '97 Grand Prix GT Coupe
    '05 Grand Prix GTP Sport Red Metalic SOLD
    '05 Grand Prix GTP Silver
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  4. #4 Re: Catalytic rattling? 
    Killa Bee Scottydoggs's Avatar
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    its gonna clog up on ya one day. so id plan to replace it.

    98 Buick Regal GS, F body brakes, Caddy STS wheels, tinted tails L36 bottom end, lightly ported heads, 1.95 roller rockers, headers, gen 5 N* 3.0 pulley, FSIC, 42 lb injectors, a BrandonHall rebuilt trans, DHP tuned and AEM water/Meth injection https://goo.gl/gpV5kW
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  6. #5 Re: Catalytic rattling? 
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    Is there a particular cat I should get?
    '97 Grand Prix GT Coupe
    '05 Grand Prix GTP Sport Red Metalic SOLD
    '05 Grand Prix GTP Silver
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  7. #6 Re: Catalytic rattling? 
    Turbo is the way to go. BillBoost37's Avatar
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    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.
    I drink..so consider that when reading my posts.

    2010 Audi A6 Dual IC's
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  8. #7 Re: Catalytic rattling? 
    Killa Bee Scottydoggs's Avatar
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    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.

    98 Buick Regal GS, F body brakes, Caddy STS wheels, tinted tails L36 bottom end, lightly ported heads, 1.95 roller rockers, headers, gen 5 N* 3.0 pulley, FSIC, 42 lb injectors, a BrandonHall rebuilt trans, DHP tuned and AEM water/Meth injection https://goo.gl/gpV5kW
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  9. #8 Re: Catalytic rattling? 
    Turbo is the way to go. BillBoost37's Avatar
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    There might be
    I drink..so consider that when reading my posts.

    2010 Audi A6 Dual IC's
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  10. #9 Re: Catalytic rattling? 
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    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.
    '97 Grand Prix GT Coupe
    '05 Grand Prix GTP Sport Red Metalic SOLD
    '05 Grand Prix GTP Silver
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  11. #10 Re: Catalytic rattling? 
    Killa Bee Scottydoggs's Avatar
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    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.

    98 Buick Regal GS, F body brakes, Caddy STS wheels, tinted tails L36 bottom end, lightly ported heads, 1.95 roller rockers, headers, gen 5 N* 3.0 pulley, FSIC, 42 lb injectors, a BrandonHall rebuilt trans, DHP tuned and AEM water/Meth injection https://goo.gl/gpV5kW
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  12. #11 Re: Catalytic rattling? 
    GXP Level Member GTPpower's Avatar
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    Some do, some don't. You're best off with a stock replacement.


    2001 GTP Drag Car - XPZ, Tischler heads, Upsidedown M90 IC'd, e85, Gen V, 2.3 w/ 5%OD
    2005 F350 6.0 - studded, deleted, tuned
    2001 GTP - cam, headers, nitrous, stock trans - 11.83 @ 116 <$2k in mods - sold
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  13. #12 Re: Catalytic rattling? 
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    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
    '97 Grand Prix GT Coupe
    '05 Grand Prix GTP Sport Red Metalic SOLD
    '05 Grand Prix GTP Silver
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  14. #13 Re: Catalytic rattling? 
    GT Level Member mguzzo's Avatar
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    rev it up and see what happens

    YouTube
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    "Silver Bullet" 98 GTP Coupe: Stock, rust free, and broadsided.
    Old '98 GTP Coupe: VS Cam, 3.0, S2IC, 42.5#, TOGs, N*/LQ4, Corsa. it once ran a 13 flat
    Older '98 GTP Sedan: Pullied, rockered, SSIC, etc. Stock 14.33 @ 96.5 / PB: 13.89 @ 101
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  15. #14 Re: Catalytic rattling? 
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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?
    '97 Grand Prix GT Coupe
    '05 Grand Prix GTP Sport Red Metalic SOLD
    '05 Grand Prix GTP Silver
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  16. #15 Re: Catalytic rattling? 
    GT Level Member mguzzo's Avatar
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    take the cat to a recycle scrap yard, you'll get about $40 for it.
    --
    "Silver Bullet" 98 GTP Coupe: Stock, rust free, and broadsided.
    Old '98 GTP Coupe: VS Cam, 3.0, S2IC, 42.5#, TOGs, N*/LQ4, Corsa. it once ran a 13 flat
    Older '98 GTP Sedan: Pullied, rockered, SSIC, etc. Stock 14.33 @ 96.5 / PB: 13.89 @ 101
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  17. #16 Re: Catalytic rattling? 
    Killa Bee Scottydoggs's Avatar
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    my scrap yard offered just the weight. seems these cats are not wanted as much as the diamond shaped cats from the 80's.

    98 Buick Regal GS, F body brakes, Caddy STS wheels, tinted tails L36 bottom end, lightly ported heads, 1.95 roller rockers, headers, gen 5 N* 3.0 pulley, FSIC, 42 lb injectors, a BrandonHall rebuilt trans, DHP tuned and AEM water/Meth injection https://goo.gl/gpV5kW
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  18. #17 Re: Catalytic rattling? 
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    I'll put it in the pile of rotors and take it all at the same time.
    '97 Grand Prix GT Coupe
    '05 Grand Prix GTP Sport Red Metalic SOLD
    '05 Grand Prix GTP Silver
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  19. #18 Re: Catalytic rattling? 
    Killa Bee Scottydoggs's Avatar
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    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.

    98 Buick Regal GS, F body brakes, Caddy STS wheels, tinted tails L36 bottom end, lightly ported heads, 1.95 roller rockers, headers, gen 5 N* 3.0 pulley, FSIC, 42 lb injectors, a BrandonHall rebuilt trans, DHP tuned and AEM water/Meth injection https://goo.gl/gpV5kW
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