Car making a scary noise
 

Hi all. A few days ago my car, 2001 Hyundai Accent, started making a clattering noise. It happens even when the car is idling, so I guess that rules out anything with the drive train. I at first suspected detonation, but I've heard that described as more of a pinging noise, and this is definitely a clatter or maybe rattling noise.

I'm not getting a CEL, and according to my scangauge, everything is normal, except the intake air temp. It read a intake air temp of 99F on a 50F day. I'm not running a WAI or grille block. Any ideas or suggestions of things to look at would be great. Thanks.

Likely it's a loose heat shield with the exhaust system -- from the header on back to the muffler.

Are you able to give more detail? Can you park the car, let it idle, and listen from the outside?

RH77

yep, sounds like a loose heat shield.

You should be able to idle the car while parked and initiate the noise by s-l-o-w-l-y revving the engine up through about 3000rpm.

At some point in there the vibrations from your engine will reach the resonant frequency of your loose heat shield and promptly set forth a cacophony of rattling. Then you can easily find it, and fix it.

It actually happens at all engine speeds. It is already pretty loud at the idle speed of about 800RPM, but then gets louder as I rev up the engine.

you need two people,
one to run the engine - one to listen for the source of the noise.
I agree from what info we have it sounds like an exhaust rattle.
Maybe a broken catalytic converter,
sometimes the strata inside break free of the casing and rattle like the chains of death.
sometimes the strata crack and separate and rattle not quite as bad.
but, back on subject,
someone with a good ear has to find the source.
Then you can decide how to fix.
Weld the broken heat shield or replace the cat?
easy enough either way.
Given that you have a Hyundai Accent, and I've worked on more than a few, I would say from the info "It happens at all speeds and is pretty loud already at idle" the front cat has broken free inside.
Pretty common on those cars.
Not real cheap to fix but definitely easier than welding. all you need are 12mm sockets and 14mm wrench,& deep socket.
Have a Friend stand in front of the car with it running and tell you where the noise is coming from before you run out and buy anything.
Hope all goes well.
S.

I'll forever have rattles, buzzes, and clatters until the entire exhaust system is replaced...

The A-pipe off of the header has a pipe-within-a-pipe, which is supposed to be secure, but hasn't been for years -- it has a resonant buzz at a variety of RPMs...especially around 1800 RPM (right about when the TC kicks-in at 35 mph). I think mid-90's Accords had the same problem with a recall or TSB. The repair is to somehow weld it into place externally, but the likelihood of it breaking loose again is noted to be high -- so it's fine :rolleyes:

I've had to remove a variety of heat shields due to obnoxious metal-on-metal rattling at any engine speed. For lower sides, the danger exists in parking over dry leaves and then interior temps for upper ones, I'm told. No biggie from the consensus.

Still, under high-load idling (fan cycling, adverse weather devices like wipers/defroster), there's another loud clatter somewhere.

The latest is somewhere back near/in the muffler at high idle. No apparent leaks or CELs. It sounds the best:

1. During EOC :D, and
2. WOT :o

RH77