theres a rattle in my voltswagen jetta trek 96 engine what could it be?

There are plenty of things it could be! Probably not your engine itself but rather something on your accessory belt. Turn the AC off or on and see if it stops. It could be your AC compressor clutch.

It can be the belt tensioner or something in the belt drive, also check the muffler support.

its the exhaust manifold heat sheild, just put some high temp rtv on the bolts and where the bolts go through the heat sheild and it will stop.

I have 2 see your car .