I have a 1993 Bonneville SSEi and I have a nasty sounding rattle at idle. Once I get the RPM over 1300 it dissapates. The motor is also acting funny, it idles fine then stumbles then fine. I have just replaced the supercharger (rebuild from Canadian Superchargers) and the water pump. I ran the car with the serpentine belts off and no noise. I tried isolating by using one belt at a time and it still had the problem. I am thinking it is the harmonic balancer. I just want to be sure though. Has anyone else ran into this problem? Could that be the cause of my motor troubles?

Sounds like the balancer to me, also. Can you grab a belt and move it enough to turn a pulley some?

That'* the key. If the balancer moves by hand, replace it.

I talked to a couple mechanics and they said it was the harmonic balancer, the only problem is getting my hands on one. I have tried a few places and no one stocks them or even orders them Autozone has one for $149 but it is a special order. Any other places to check?

I ordered mine from gmpartsdirect.com. Cheaper, but you gotta wait a few days. maybe Napa has one?

Rock Auto has a replacement harmonic balancer that is the same as the GM OEM balancer. It'* about $98.00.

www.rockauto.com