Just got a call from a friend's father; he says he's got a rattle under his '87 Camaro that he can't find. He says it's on the right side, and sounds like it's near the cat, but he doesn't think it is the cat. The car rattles when you first start it up, and will rattle in park, or, when it's in drive with the brake on. He says if he rev's the motor up a bit, the rattling stops. He says, too, that if he turns the Camaro off, he hears the rattle after the motor stops.

I was thinking the catalytic convertor bed had broken up, and was rattling- but wouldn't it rattle even worse when he raised the RPM's? My only other guess is that the cat's hanger or heat shield has loosened up.

 

Could be heat shield or cat. Another possibility is the starter drive is not retracting after the engine starts & finally does after the engine gets revved a few times.

 

its almost certainly the cat, I had the exact same problems with my car when I got it, try unbolting the back of the cat and looking in to see whats up. when I opened mine up I found every thing was gone so I figured cool, I wont have to gut it my self, then I found all the pieces in the pipe going to the muffler.

 

Thanks for the info guys! I'll get to look at the car this weekend; I'll post what I find!