Hey guys,

I believe my cat is dead (not a kitty cat haha)

On Monday i drove to school and everything was fine. I went to go out for lunch and as I was driving my car sounded like a lawnmower when the engine was put under load. The sound sounded like it was coming from the manifold/dp area under the dash.

So last night I jacked up my car, took off the bottom heat shield and inspected the flex pipe for cracks or holes. Nothing, took the top heat shield off and nothing on the top. so i ruled that out. next I banged on the cat with my hand. and it sounded like i had marbles banging around inside of it.

So im guessing my cat is disintegrating and needs replaced. so my options are

-zzp catless dp
-zzp catted dp
-gut the cat
-buy a cat off a local (outtamymind, a.k.a steve) and weld it in
-get a whole new dp and cat from a muffler shop

What do you guys think?


Car is a 2007 G5 GT with 116,000kms, stock

 

i know you said "not a kitty cat", but I was still waiting for the part where you say "i found a cat stuck in my serpentine belt"

 

lol if the cat was bad then it wouldn't sound like marbles rolling around it would be solid

 

hey, bud I just had this problem in my G5 GT, check the flex pipe on the down pipe and replace your cat.


the flex pipe moves under load, expaniding causing the noise. at least in my case.

just read the whole post.... haha flex pipe is good?

 

my flex pipe was fine.

 

you won't be able to see if it's fine or not they get "pinhole" sized holes in them....accordian pos "flex pipe" ftl

 

The cat is bad if it sounds like marbles when hit. This means the catalyst has broken apart. There are different ways the catalytic converter can fail. Doesn't always just smell like eggs.

Can't go wrong with a ZZP piece, either way.

I do not endorse gutting the stock cat. the large empty chamber will not only sound like ****, it will create a large area of turbulence which will interrupt the exhaust gas scavenging properties of the exhaust, resulting in a loss of power.

 

im stock 170bhp haha it cant get any worse. i dont race so its the cheap solution

 

if it sounded like a lawnmower with a dead cat then don't you think a catless would sound the same??

Just some food for thought

 

no haha its the "marbles" banging around so fast. thats what i hear

 

ZZP's header/DP combo with high flow cat

 

mine was solid with some chunks at the point closest to the motor lol

 

yea mine sounds bad and its only getting worse. it didnt do it at idle before and now it does

 

If you want a stock downpipe, I have one laying around.
Its off my 06 2.4. has about 80 000 km on it. works just fine.

 

I would get the ZZP 2.5" downpipe with cat. If you do the 3" you're more likely to eventually throw a cel. I noticed better fuel economy with a better flowing downpipe as well. You might appreciate that since you are not doing other performance mods.

 

This.

At least someone on this website understands fluid flow

 

I HATE OUR CATS!!

i got mine replaced for free by GM ( i dont have a gm warranty either) for free, before i had a modded exhaust.

now the new cat they gave me is defective and my exhaust is modified... i'm looking to just find another stock one and replace it, but that buzz sound under load just sucks!

 

im talking to my dad tonight about a zzp 2.5" catted dp. its probably the cheapest option other than catless. would i need the extra O2 bung?

 

Only need the bung if you are going to run a wideband.

 

If you plan on tuning it the extra O2 bung is a good idea for later

 

It's not the cat.

It's the tune.

The stock cat is a high flow unit (on the SS/SC), and is fine. The general cause for them to fail is an overly rich tune.

 

This.

 

Bring it in to the dealer. Cat should be covered on an '07 for 8 years 130,000 km
GM Total Warranty | Bourassa Chevrolet Buick GMC

 

GM bumped it up to 10 years 120,000 miles.

 

i got a stock downpipe with maybe 5000km's on it. i'll sell it to you for $100 jordan