Crazy sound. My 99 sounds like a fan is loose or sounds like when you put a playing card on a bicycle rim (none of you younger guys ever did that). It is a flutter that sounds like the fan. It comes and goes especially when I slow down at a red light. It sounds louder and it even sounds at idle for a while. Sounds like it is coming from under center of the car. What can that ber? Hope its not the wheel hub etc. Also, I was getting a PO300 trouble code and changed the plugs and wires. You think that kmight have something to do with it?

Sounds like it is coming from the AC compressor. Anybody knows what it might be?

Ours does the same thing. I tried a bit of spray lubricant on the AC clutch without getting it on the belt, of course, and it got a bit quieter. I just accept this as normal. My cavalier does it sometimes too.