What is the most likely cause of black smoke from the exhaust?

The presence of black smoke from the exhaust is primarily associated with an excessive amount of fuel being injected into the engine, which leads to incomplete combustion. A malfunctioning electronic fuel injection system can cause this by delivering too much fuel for the air available in the combustion chamber. When the air-fuel mixture is too rich, not all of the fuel can be burned effectively, resulting in black smoke.

This excessive fuel can stem from various issues related to the electronic fuel injection system, such as faulty sensors, a clogged fuel injector, or a malfunctioning engine control unit (ECU) that miscalculates the needed fuel for optimal combustion. The rich mixture can also lead to poor engine performance and increased emissions, further highlighting the importance of resolving any issues within the fuel injection system.