My 2002 4WD has what seems to be a rattle associated with the engine. Sound is not perceptible at idle. Varies with RPMs but will go away if I get on the throttle a little. Can’t hear it under the hood—purrs like a kitten and doesn’t rattle if I rev it up.

Is it common for a heat shield on the cat to rattle? Possibly the heat shield near the exhaust manifolds? Sounds like it may be coming from the right side of the vehicle, which is obviously where the exhaust is.

 

Recently I had a strange rattle. I turned out that the weld where the exhaust pipe exited the muffler gave way!

Sounds can travel in weird ways. When it comes to diagnosing them, I'd suggest you don't get too focused on from where it seems to originate. I'd focus on the details of what it sounds like to help find its source.

 

I’m going to have to enlist the wife for throttle duty while I climb underneath.

Cat was replaced so I will focus there first.

 

To be honest, if my Blazer didn't have any rattles that is when I would start worrying. I bought mine new and I think in the first hundred miles I had rattles. Fixed them and not long after that more came along.