My car have been designating black smoke once the engine is one and also while the car is on the move. Consequently, this has resulted to outrageous amount of high fuel consumption rate. I have checked the fuel line regulator and also the airflow meter, yet the problem persists.
The place to start is by checking for diagnostic fault codes. If there's a code related to a misfire, address that first. If there are no fault codes, you'll need a scanner to view live data. You'll need to interpret the sensor readings to see why the Engine Computer is commanding so much fuel.