Black Soot On Exhaust
If you have black soot from exhaust, your engine’s air/fuel mixture is too rich. The fuel that isn’t burned in the engine is mostly burned by the catalytic converters, while the rest shows up as soot. This isn’t uncommon on diesels, which use precise fuel metering to control engine speed. If your car has a gas engine, something is throwing off the air/fuel mixture. This could be as simple as a dirty air filter keeping the engine from getting the oxygen it needs for combustion. A stuck injector, or problems with the fuel pressure regulator or engine sensors could make your car’s fuel injection system to add too much fuel.