TM 10-3930-669-20 5.  EXCESSIVE SMOKE (CONT). KNOWN INFO TEST OPTIONS Fuel filter OK. Air filter OK. Air intake system not leaking. Fuel connections not leaking. Visual inspection. POSSIBLE PROBLEMS REASON FOR QUESTION Fuel injector(s) faulty. Air intake obstructed. Fuel injector pump faulty. If the engine is running roughly or missing,  a  fuel  injector  may  be clogged. KNOWN INFO TEST OPTIONS Fuel filter OK. Air filter OK. Air intake system not leaking. Fuel connections not leaking. Fuel injectors OK. Visual inspection. POSSIBLE PROBLEMS REASON FOR QUESTION Air intake obstructed. Fuel injector pump faulty. If the air intake system is damaged  or  obstructed  the  fuel air mixture may not have enough air. ¬ ¬ 2-78