i have a 2000 gmc dually 4x4 pick up truck when in park it wants to sugers on me and shoot black smoke.

may be a vacuum leak or a bad mass air flow. have it checked for codes and see what comes up.

Roy

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.