Marbles in a can sound only during engine braking?
 

Hey all,

I recently scraped my car pretty bad hauling around 4 people in my car including myself, and my car already rides really low, with 4 people it will scrape on anything. I mean ANYTHING. Well anyway it was pretty bad, and now I have this odd sound that only occurs during deceleration when I'm engine braking. I've tried searching and the regular MIC symptoms don't really match up with mine in that you can hear it all the time, but in my case only during engine braking.

If I have time today I will post a video so you can hear it. It seems to get louder and more noticeable as the car heats up. There's also something rattling when I go over bumps ever since that scrape so it makes me think it's exhaust related, maybe an exhaust leak. My tranny seems fine so I don't think it's leaking or anything.

Any ideas?

You may have smashed the ceramic catalyst structure, it being a low point.

That would rattle in the exhaust all the time.

That could be it, in that case it's midpipe time! In that case I'm actually not upset. But will it cause damage if I drive on it like that? Or only until it clogs and I start losing power?

I've noticed it's been misfiring a lot lately even though I have a brand new ignition (coils, plugs & wires). Could it be oxygen sensor related?

Here's a link to the sound, my phone makes it sound a bit worse than it is but that's basically what I'm hearing every time I let off the gas.

http://youtu.be/RF7ySGWg77A

Bump

That sounds scary... I would at least drop the mid pipe and investigate the cat's condition.

Pull your Cat off and look inside. Sounds like you broke the cat element.

Either that or you knocked the exhaust loose and now it's rattling around.

I had the same noise and the cat had shattered inside. We put a camera down the pipe to see there was 2 big holes in the cat. I had to have a new exhaust because the pieces if cat can block the exhaust and cause damage to the engine.

Hmm... guess I need to invest in a whole new exhaust. BHR midpipe + Borla? :D

Check to see if the catalytic converter hangar is rubbing against that pinch weld right there. I scraped super bad one time and it bent the exhaust upwards and now that hangar rubs and makes all sorts of annoying as hell noises.

I'll take a look at all of that when I have the car up in the air next weekend.

So it turned out to just be something bent around the rear control arm area rattling. It got bent back and the sound is completely gone. It makes sense... it only happened when going in reverse or engine braking. Where the rotational force was in the opposite direction.