On May 30, 2003, at 1445 eastern daylight time, a Cessna 172N, N734AG, registered to Corsair Enterprise Incorporated and operated by a private pilot, conducted an emergency landing in a field following a loss of engine power near Orangeburg, South Carolina. The personal flight was operated under the provision of Title 14 CFR Part 91, and visual flight rules. Visual meteorological conditions prevailed and a visual flight rules flight plan was filed. The airplane was destroyed by fire, and the pilot reported no injuries. The flight departed Orangeburg Municipal Airport, Orangeburg, South Carolina on May 30, 2003 at 1425. According to the pilot, during pre-flight procedures, he noticed that the mixture control was "stuck fully open" and was not placarded or written up. The pilot elected to make the flight despite this finding. The pilot stated that it "did not appear to affect the airworthiness" of the airplane. Approximately 20 minutes into the flight the airplane had a partial loss of engine power. The pilot declared an emergency and requested assistance from Columbia Tower. The airplane regained engine power and the pilot elected to return to the departure airport. On final approach, the airplane had a complete loss of engine power, and the pilot conducted an emergency landing in a field. After landing without incident, the pilot observed flames exiting the cowling. Efforts by the pilot to extinguish the fire using the onboard fire extinguisher were unsuccessful, and the airplane was destroyed. The pilot stated that prior to the accident flight he taxied the airplane to the fuel pump, and had to shut off the engine by turning the magnetos to the "OFF" position. The pilot also stated that the mixture control lever was stuck in the rich position. Examination of the carburetor showed the mixture control linkage was corroded and not moving freely. Further examination revealed an incorrect bolt had been installed for the mixture control linkage. According to the parts manual for the Cessna 172, bolt number S2323-13-6C-38 is the correct bolt for the mixture control linkage. The bolt found installed on the accident airplane was an AN3 part numbered bolt. Federal Aviation Regulations Part 91.7 (a) states that no person may operate a civil aircraft unless it is in an airworthy condition. According to FAR Part 91.7 (b), the pilot in command is responsible for determining whether the aircraft is in condition for safe flight, and shall discontinue the flight when unairworthy mechanical, electrical, or structural conditions occur.