For some reason my cat rattles..REALLLLLY loud when my car is idling sometimes. I'm almost positive it's the cat, because I was in the driveway and heard it loud and clear and stuck my head down next to it and sure enough, this rattling seemed to eminate from the cat. Now, this is no LIGHT rattle, it's damned loud. Any ideas on what it is off the bat? I'll be under the car examining tomorrow, so any heads-ups would be appreciated :P

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1992 Camaro RS (Auto)
-
Performance mods
NOS (100 HP shot)
Dynomax cat-back exhaust
Hedman headers
K & N open element/ X-Stream lid
MSD 6A ignition
Under drive pulleys
LT1 camshaft
Coming soon:
1.6 roller rockers
Torquer heads
Edelbrock TBI/intake

Audio
Sony Xplod CDX-M610 head unit
Pioneer 2-way 4x6 front speakers
Pioneer 3-way 6x9 rear speakers
12 inch Pioneer VCCS PRO subwoofer
QLogic sealed box
Kicker ZR360 amplifier
Lightning Audio 1 farad capacitor
Other
Macewen White Faced Gauges/Shift overlay
A-pillar gauges (Phantom oil pressure, Air/Fuel)
180* thermostat
Window Tint
Under car neons (green)

 

Well, if it's coming from the cat, I'd bet it's .... {drum roll please} the cat.

But seriously... its insides have probably broken to pieces as they frequently do. You need another one.

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"So many Mustangs, so little time..."
ICON Motorsports

 

Yeah, sounds like the substrate inside is banging around inside the converter housing. The only way to fix is to gut it, or replace it.

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Hey, my cat is making the same kind of racket. Thing is, is i just had mine replaced!

Should i go back and have then check it out? They mechanic who installed it is a well known rip off artist. (of course, i find this out afterwards...)

Are you guys sure it means the CAT needs to be replaced?



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1986 IROC Camaro
305 TPI "LB9"
3.23 gears
Doesn't know enough about cars.
AIM: jesusathome

 

Dude I feel your pain. All my problems started this exact same way.

 

No, I'm not sure YOUR cat is rattling, but if it is, more than likely the substrate is loose and rattling around inside the casing.

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If you live in Southeastern US, check us out!
South East Thirdgen

GM Master Tech
ASE Master Tech + L1
Savannah, GA

'87 Trans Am
S/D TPI retrofit including functional PassKey,
22# injectors,
Whatever chip I feel like burning,
JET AFPR, Ported Plenum,
TB Coolant Bypass, Custom Cold Air,
SSM SFC, KYB Shocks, Boxed LCAs, Wonder Bar,
8mm Accel wires,
Flowmaster Exhaust,
16" GTA rims,
Corvette Servo,
3.73 Posi
4wheel Disc Brakes
Summit 1-5/8" headers, 2.5" Dynomax catback.

Best 1/8: 9.519@72.74

'97 Bonneville SSE

 

Over time Cats deteriorate and thats why they rattle. Either remove it or replace it with a random technoligies cat or equivilent.

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iso 91/92 camaro. 96Z M6 subframe connectors, boxed trailing arms, tubular panhard rod, BMR stb, SS rims, 6 point cage, other misc. debris

 

Could be just the heatshield on the cat if it is remove it the floor heatshield is sufficient.

 

my cars making the same sound but its a very soft rattle. I heard it right after i went over some speed bumps and hit the cat a little.

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1988 Sport Coupe 305 TBI
K&N
Flowmaster exhaust


Daily driver:
1988 K1500 5.7 4x4 shortbed flowmaster cat-back gutted cat.
AOL: RyanNH84

 

Yeah- don't forget about the heat shield/stone shield. It's only welded on at the corners. If one of the welds breaks it's gonna create a lot of buzzing/rattling. Or sometimes they can get bent/tweaked and lay directly against the body of the cat- same problem.



[This message has been edited by Damon (edited July 23, 2001).]