what the heck is going on.. exhaust rattle/shaking

[cam98aro]

ok, so last night i went and got some gas, my car seemed 100% normal

when i get back in my car and start it up, it is running really rough and shaking, and my exhaust sounded different

at first i thought it could have been a misfire, because of the changed exhaust noise, but then i thought it might be the IAC acting up

so i drive away, and my car seems fine, but louder

so when im driving today, i notice that my car seems a lot louder than usual, idle was perfectly fine, just the car was louder

i also noticed that my exhaust rattle has also somewhat disappeared, now this rattle REALLY sounded like it was coming from the front of the car, but maybe im wrong.. the rattle was there sometimes, but for the most part it seemed fine

so what do you guys think this could be?

-cat broke inside?
-resonator went bad? (IIRC we do have resonators.. little square boxes on the exhaust somewhere??)
-muffler broke?

i just think it is weird that my car was running rough, then all of a sudden it gets louder out of nowhere, so im thinking something dealing with backpressure, which would make me think the cat

[ne0hisda0ne]

Re: what the heck is going on.. exhaust rattle/shaking

You sure your headers didn't fall off?

[pace2006]

Re: what the heck is going on.. exhaust rattle/shaking

How old is the cat in your car? You might be having some problems with the internals blocking it up. They have a tendency to rattle when they're going out. Also check to see if the welds on either side of it are still together. One of mine had broken and caused an awful rattle at lower rpms.

From what I remember our cars don't have resonators. At least, I don't remember seeing one on my car's piping when installing the headers.

[ne0hisda0ne]

Re: what the heck is going on.. exhaust rattle/shaking

I would agree with pace, but if your rattling stopped and it's louder now, I don't think that would be it...I've gone through plenty of cats and well when the rattling stops is when the honeycomb has fully broken up and then shoved itself into your exhaust piping, which would cause the exhaust to sound lower, not higher...more wheezy, constricted than anything...

check your header bolts...is your cat bolt on, check to make sure it didn't slide off....

[Smoke Panther]

Re: what the heck is going on.. exhaust rattle/shaking

Check your heat sheilds. Look for random sheets of metal on the underbody, near the primaries and y-pipe, and make sure they're securely in place

[cam98aro]

Re: what the heck is going on.. exhaust rattle/shaking

th cat is what im assuming is the stock one.. if its not stock, it was a factory replacement, and was welded back on.

the car has 136,000 miles, and i have been battling this rattle for what seems like forever now.. over a year and probably 15,000 miles

my rattle only happens when there is a load on the engine and when i press the clutch in to shift, it rattles when the rpms go down.. there seems to be a sweet spot, when i shift around 2500rpm it almost always rattles, but usually only going from 1st to second, and when i engine brake, it rattled a hell of alot

last time i was under the car i checked the heat shields and they seemed fine, but i dont think that they are the problem since after my exhaust got louder all of a sudden it is rattling a lot less

but yeah, the car just seems to be noisier now, doesnt seem to have lost any power or anything like that

edit* oh yeah, it seems louder at the back of the car, like the muffler is bad, or like i just have a complete straight pipe in there.. its not obnoxiously loud, but loud enough for me to have noticed it

[Blizzard242]

Re: what the heck is going on.. exhaust rattle/shaking

Common, if the car's exhaust tone is different and there is/was a rattle. It's got to be the cat. And stock exhaust doesn't have a resonator. Possibly the ceramic or whatever is in the cat, after breaking down it can still get hot as hell and burn/bubble through the cat casing. Get under there and check it out.

[Fondle]

Re: what the heck is going on.. exhaust rattle/shaking

maybe one of your manifold/headers bolts came loose

[ne0hisda0ne]

Re: what the heck is going on.. exhaust rattle/shaking

Common, if the car's exhaust tone is different and there is/was a rattle. It's got to be the cat. And stock exhaust doesn't have a resonator. Possibly the ceramic or whatever is in the cat, after breaking down it can still get hot as hell and burn/bubble through the cat casing. Get under there and check it out.

yeah I came back to post this exact thing...if the pieces that broke up in the cat were small enough they could of made it past the prolly stock piping through your muffler and out your tailpipes...well it would basically make sense why it's louder and no rattle now...so yeah I think pace hit it right on the head...would of mentioned that...but with all your 3,000 posts I figured you'd know to check there first...so I didn't and i've never successfully blown honeycomb through my stock exhaust 'yet'. basically you have a straight pipe now...ha!

[cam98aro]

Re: what the heck is going on.. exhaust rattle/shaking

Common, if the car's exhaust tone is different and there is/was a rattle. It's got to be the cat. And stock exhaust doesn't have a resonator. Possibly the ceramic or whatever is in the cat, after breaking down it can still get hot as hell and burn/bubble through the cat casing. Get under there and check it out.

maybe it is the ls1's that have a resonator then.

it still could be that something in the muffler blew out

like i said it is louder at the back of the car at the muffler, it sounds like i put an aftermarket muffler on my car

i will get under the car and look at the cat

[ne0hisda0ne]

Re: what the heck is going on.. exhaust rattle/shaking

easiest way to check is to tap on it with either your hand or a rubber mallet, if you hear rattling your cat is dead. Then again you might of blown it all out and there will be no rattle... tap all around, don't just tap on the side...

[ne0hisda0ne]

Re: what the heck is going on.. exhaust rattle/shaking

oh, also I guess if it's blown out it may make a hollow sound (echoey)...that too will tell you if it's a bad cat or not...if your still not convinced, climb under someone elses car and tap on their cat and see if there is a difference in tones.

[cam98aro]

Re: what the heck is going on.. exhaust rattle/shaking

i found the problem

i have a factory dual exhaust that i bought off of a member here, from a v6 camaro, and the weld that the pipe goes into was shot and blew out

after i drove today my exhaust tips were like 3" from dragging against the ground haha

its weird because you would think that, that would be a problem that i would notice, not just all of a sudden happen when i start the car.. unless the shaking of the engine starting snapped the weld and it got loud.. still not sure if that would cause the engine to shake and run rough.. maybe because there was less back pressure?

[Blizzard242]

Re: what the heck is going on.. exhaust rattle/shaking

Factory dual exhaust? You make no sense.. Make sense. I'd would normally assume you're talking about Dual tips.. But then you'd have to have the y87 package I believe but you haven't mentioned that. But you haven't mentioned anything about anything. So.. What happened with what?

[pace2006]

Re: what the heck is going on.. exhaust rattle/shaking

factory dual exhaust? You make no sense.. Make sense. I'd would normally assume you're talking about dual tips.. But then you'd have to have the y87 package i believe but you haven't mentioned that. But you haven't mentioned anything about anything. So.. What happened with what?

vvvvv

i have a factory dual exhaust that i bought off of a member here, from a v6 camaro...