there is a few rubber exhaust hangers, if they break the exhaust can rattle, also you have heat sheilds that point the heat away from the passenger compartment, with the car off, tap the exhaust pipe with your foot at the back of the car and listen for a corresponding rattle.
Heat shield on your exhaust system?
There could be hundreds of different things that could rattle. Give us more details. A common rattle is from the catalytic converter. The inside breaks and pieces get into the exhaust and rattle.
No who, but what. All internal combustion engines emit exhaust fumes.
You need to check all the exhaust pipe hangers, one of them is letting the exhaust rattle against something. Also check muffler heat shield it could also be loose. When transmission in engaged in any gear the engine is torqued to the right, so that is moving the exhaust ( it is attached to the engine so it moves with the engine )into a position to rattle, in neutral the engine is sitting evenly in its mounts so no rattle. May want to check engine and trans mounts too.
car exhaust or waves
A car pollutes by emitting fumes from the exhaust. The less efficient a car is, the worse the pollution is.
rattle (car noise) = nekisha (נקישה)
What can cause black sooty exhaust is bad valve guides. When the guides are bad oil leaks into the cylinder when the car isn't running. When the car starts it produces black exhaust.
Becuase there is trash in it, or your exhaust is loose.
You need a new Head Gasket.
Catalytic converters do not rattle. If it does it will need to be replaced as it may block the exhaust. Loose heat shield?