When my car is at idle or going really slow I'm having a horrible rattle or clanking noise. If I sit in park it does not do it. It'* really hard for me to describe.

Sounds like the harmonic balancer. With the car off, pull the belts back and forth and watch the crank pulley. It SHOULDN'T move.

Does the noise go away if you firmly accellerate?

I recently had a very similar issue. When the car was warm and at low idle in gear, it made a terrible clanking/rattling noise. Raise the rpm'* slightly and it disappeared. Bill is right, it could very well be the balancer, but mine was something else. I had a buddy sit in the car with the brake on, in gear, while it was a low idle. I could see the tensioner pulley jumping back and forth making the noise. I fixed it by replacing the pulleys when I replaced my timing belt. Seems like one of the bearings was grabbing enough to cause the belt to jump at those low rpms. Granted, your a 96 vs my 93, but it is something else to check.

???

OK, Let me translate from the language of having driven 450 miles today and not eating until 8:30pm:

belt meaning chain

my bad, i replaced all of that stuff while i was replacing the timing chain set.

sounds like it'* coming from the rear as well...

But it does go away when I'm accelerating.

Have you checked the catalytic converter? Its possible that the converter has decided to come apart on the inside. I would crawl up under the car and check this, along with the heat shields.

Yeah... if I only knew what any of this is. I had a talk with my uncle... he'* going to check it out on saturday

I have a terrible rattle or perhaps I would decribe it as a sloppy gear or growling noise - it happens much , but not all of the time, at idle in my '95 supercharged SE. It stops if engine speed is very slightly increased. I think it is balancer shaft and its gear drive off of the timing gear. I just replaced intake gasket and timing cover gasket so I had a "look and feel" at the balancer shaft and it seems to have a lot of endplay which would seem to cause the gear drive noise that I think I am hearing. I don't know what affects endplay or if this is the cause of the problem, but I left as is. The gears looked fine and the bearings had no slop...it did not seem to have up/down play. I don't know exactly what is causing or why it started but I am not going to pull the motor. I just hope it does not get worse and this thing holds together awhile. My problem is not a pulley.

Just prior to this noise showing up I also just had the balancer break and it caused more of a combined rattling at idle and frequent severe knock sound just after throttle was released. The rubber hub had completely broke. I also just happened to have a timing cover massive oil leak near oil passage, which I have since fixed. This car seems to be falling apart - is this bad coincidence?

The supercharger has always been noisy since I bought this car with about 25k. Current mileage is 130k.

99% of these problems will be either the Supercharger Coupler (if equipped) or the Harmonic Balancer.

Rarely will it be a balance shaft or timing chain related problem, unless you're well over 200,000 miles.