What Causes Black Smoke from a Gasoline Engine?

[AngelaMarie]

Black smoke from a gasoline engine occurs when the air-fuel mixture is too rich during operation, meaning the excess air coefficient in the cylinder is too low, leading to incomplete combustion and the emission of carbon particles, resulting in black smoke from the exhaust pipe. The causes include: 1. Vehicle overload or engine overloading; 2. Insufficient cylinder pressure and excessively low engine temperature; 3. Improper carburetor adjustment; 4. Clogged air filter element; 5. Misfiring in individual cylinders and delayed ignition; 6. Poor sealing of intake and exhaust valves, leading to inadequate compression of combustible gases, worsened combustion, and increased smoke emission. To address the issue, promptly check if the choke valve is fully open. After turning off the engine, inspect the carburetor nozzle for fuel spray or dripping. If necessary, adjust the float fuel level height, tighten, or replace components.