Discolored vehicle exhaust is a telltale sign of a foreign liquid inside of the cylinder combustion chamber. Black smoke indicates the air fuel mixture is rich. Black smoke is caused many ways, including issues with the spark plugs or air filter.
The combination of air and fuel combusting inside of an engine cylinder creates horsepower and torque. When the air fuel mixture is heavier in gas as opposed to air it is considered rich. A lean mixture is heavier in air.
Dirty spark plugs cause black exhaust smoke. Dirty spark plugs do not fire into their specified cylinder at the right time, which forces an unburned air fuel mixture into the exhaust system.
A dirty air filter is a very common reason for black exhaust smoke. Dirty or clogged air filters reduce the amount of air injected into the air fuel mixture while the amount of fuel used stays unchanged.
Black smoke is an indication your vehicle is not running efficiently. A rich air-fuel mixture burns more gas, reducing fuel efficiency. Drivers may also smell a gas odor.
