Black smoke indicates too rich of an A/F mixture
Probable causes of an engine running rich are as follows:
1. Excessive fuel pressure can be cause by restricted fuel return line
2. Defective Oxygen Sensors.
3. Leaking injectors and fuel pressure regulator.
4. Coolant temperature sensor out of calibration.
5. Restricted air intake system.
Tuesday, March 20th, 2012 AT 11:59 PM