bulletguy

The shiney cover behind serpentine belt tensioner is vibrating/shacking. Is this normal?
What is this part called?

DiabloX22

That is your drive belt tensioner. Its going to move some especially during start up and until the engine is at operating temperature. I just bought a new 1 for mine. With the engine cold, pull up on the belt, if you get excessive play, you need 1. I found mine is noisy if I put the ac on while its idling I hear a noise that sounds like metal grinding. After looking into it, its common. Let me know if you have any other questions.