Ok, I've searched the forums here, and I can't find anyone with a problem exactly like mine. So I figured I'd post this thread and hopefully get an idea or two.

Lately, when I first start my car, I can hear this like marbley rattle kind of noise. It's really hard to explain. If I start it, then rev it a little bit right after it starts making the noise, then the noise goes away. It only seems to do this at idle. Also, if I turn off the engine and restart it, it will repeat itself. It rattles at idle again until I rev it up, then idles without the noise.
I'm trying to pinpoint exactly where it's coming from, but it seems to spread all over the place.. First I thought it might be in the flexplate/transmission area, but then it kind of sounded like it was around the front by the harmonic balancer. Even with a piece of long hose held up to my ear I can't quite pinpoint it.

Does anyone have any idea as to what might make this noise? It's really weird how I can rev it and it goes away..

Oh yeah, if I shift the car out of park and into drive, the rpms drop down a little bit and the noise will stop then too.

 

Mine does the same thing. It's parts of the CAT hanging in the exhaust pipe. I have tried everything but I am gonna have to cut it out. Mine does is when I am warming my car in the morning but once it kicks down it goes almost all away.

Trey

 

Does yours kind of sound like it could be coming from the front of the engine too? That's why I'm kind of worried. I was thinking maybe it's something internal.

I'm not sure though, I'm thinking since it goes away as soon as I rev it or shift into gear, it can't be anything too serious.. I hope.

 

Sounds from the exhaust can be very deceiving. I thought it was a lifter going out. I ripped into them re adjusted and still there. So I went and bought a new engine put it in and it was still there. So I took it to a buddy of mine and he laughed at me telling me I just swapped motors for something in my exhaust

 

+1 for busted up guts in the cat. Mine did the same exact thing until I gutted it. Kinda sounded like rocks in a coffee can when it was idling.

 

Hmm, I really hope it's not the cat. I just replaced it about 2 months ago. Could it really go that quick?

 

Well, I just came back from a drive to the autoparts store, and now the stupid thing isn't making the noise. It did this once before, it made the noise for a day, then it stopped all together for awhile. It's really weird.

 

i recently discovered the same noise. however i do not have a cat on the car. i scoped the entire engine and could not find it either. i have a 5 spd. and thought its in the trans somewhere. the noise comes and goes even when shifting. i did notice some oil around the distributor and checked to make sure it was tight. i suspect something came loose there or in the tbi as well. im still looking but also can use some input.

 

Does yours generally only do it when the car is warm? My car only seems to do it if it's warm when I start it.. If I just come out to it in the morning and it's cold, it won't do it at all. The thing about mine though, is I only really hear it at idle, if I'm moving I never hear it (not to say it's not there though).

 

mine has a similar rattle too, only at idle, on mine I'm 99% sure it's the belt tensioner, but now my tired old lo3 is also making a really bad ticking/grinding noise so I think its days are numbered anyways

 

Oh wow, I forgot I made this thread. I'm actually pretty sure I figured out what it was.. I had a loose exhaust hanger, I tightened it up and haven't heard that noise ever since. So that was hopefully it.