Catalytic converter question [Archive] - Forum


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05-22-2008, 09:45 AM
Would like some input/advice/info. If the cat was going out on my GT, what kind of symptoms or noises would I be noticing/hearing? It's the original cat, and my car is a 2000. I'm getting some unusual noise(s) from my car and I'm wondering if it could be the cat. It doesn't seem like the noise is suspension or wheel related. Just want to know what I'd be noticing or hearing if my cat was starting to go. Thanks.

05-22-2008, 09:52 AM
Well the noise you'd get it rattling, jack up the car and knock on it. It could very well be that you have a loose heat shield that's making noise. If it wasn't doing it's job, you'd be getting an O2 sensor code. and I believe there's a stench from it when it goes bad.

05-22-2008, 10:14 AM
It's definitely not the heat shield. Not throwing any codes as of yet either.

05-22-2008, 01:22 PM
Any power loss?

05-22-2008, 02:48 PM
When mine went out three years ago I didn't hear anything unusual, but my car was completely bogged down. If I got on the throttle at all it would almost die.

05-23-2008, 07:16 AM
No loss of any power...atleast not as of yet. I know that would mean the cat was plugged. It's definitely under the category of a "rattle" type of sound, but it's not the heat shield. I originally thought that it could be wheel/suspension related, but it's not. I only really notice the "rattle" noise, when I accelerate quickly from a dead in kind of jumping on the accelerator a bit. If I accelerate slowly, I don't hear the noise at all. I've read that the insides of cats can break down or loose, which can cause the rattle noise, and this sounds more like this type of rattle to me. Once I get into the higher gears, the noise is pretty much gone, or not very noticable. It's hard to tell if it's still there because of my Flowmaster muffler. At idle in park or neutral, there is no noise/rattle, even if you step on the gas. If it was a cat rattle, wouldn't it rattle then too?

05-23-2008, 08:26 AM
I just got a new cat for my GA. No codes, but it would rattle loud right after I started my car and go away when the car is warm. The car accelerated very poorly.

05-23-2008, 08:59 AM
would you notice a drop in mileage with a cat on the way out?

05-23-2008, 09:35 AM
I would say so....because it's like blocking the exhaust.