I have a 99 E320 4Matic, and after driving today I noticed that it is making a noise that it has never made before and doesn't sound healthy.

The best way to describe it is that it sounds like an old diesel at idle. It has a pretty bad rattle to it, anyone know what this could possibly be?

 

Check plugs, wires, coil packs. Does it lose power or stall out?

 

it runs completely fine, it just chatters like a diesel at idle

 

You can hear the sound more under the car compared to the engine bay if that helps at all.

 

anyone? [&:]

 

leaky exhaust?