- Dirty or restricted air cleaner systems
- Dirty Loading the engine
- Poor fuel quality
- Cool operating temperatures
- Excessive carbon build-up in combustion and exhaust spaces
Black smoke can occur across the entire operating range, but is usually worse under full power, or during the lag before the turbocharger boosts air supply to match the fuel usage such as in the early stages of acceleration and during gear changes. Moderate turbo lag smoke is acceptable; otherwise black smoke should be hardly visible in a correctly running engine.