NTSB Probable Cause

THE PILOT-IN-COMMAND'S FAILURE TO MAINTAIN AIRSPEED WHILE MANEUVERING TO RETURN TO THE DEPARTURE AIRPORT, RESULTING IN AN IN FLIGHT LOSS OF CONTROL, STALL, AND IN FLIGHT COLLISION WITH TERRAIN. FACTORS RELATED TO THE ACCIDENT WERE: PARTIAL LOSS OF ENGINE POWER DUE TO FOULED IGNITION POINTS, CONTAMINATED FUEL, IMPROPER MAINTENANCE AND IMPROPER PREFLIGHT INSPECTION BY THE PILOT-IN-COMMAND.