On November 25, 2015, about 1000 mountain standard time, a Piper PA-28-140, N7PM, was substantially damaged when it was involved in an accident near Wickenburg, Arizona. The private pilot and flight instructor were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight. The instructor stated that the purpose of the flight was to familiarize the pilot with the airplane before he purchased it. After completing maneuvers, they returned to the airport to conduct practice takeoffs and landings. While on the base leg of the traffic pattern for landing on runway 5, the pilot applied engine power to arrest the airplane's rate of descent; however, there was no response from the engine. The instructor verified that the carburetor heat was on and the mixture was in the full-rich position, and noted that the fuel selector was on the left tank, which contained full fuel. The instructor stated that he was able to produce a response from the engine by "pumping" the throttle; however, it was not adequate to sustain flight, and the pilot performed a forced landing to desert terrain. The airplane came to rest upright and sustained substantial damage to both wings, the fuselage, and empennage. About 20 gallons of blue-colored fuel was drained from the right wing fuel tank. The left wing fuel tank was breached during the accident sequence. The airplane was recovered to a secure storage facility for examination. Visual examination of the engine revealed no anomalies. A test run of the engine was attempted, but the engine could not be started. Further examination revealed that the mixture control cable clamp was missing, which allowed the cable to flex and resulted in no movement of the mixture control arm. A makeshift clamp was fashioned and a second engine run attempted. The engine started, accelerated smoothly, and ran without hesitation through various power settings. Review of the airplane's maintenance logbook revealed that the engine was removed, disassembled, and inspected following a propeller strike in November 2014. The most recent annual inspection was completed the month before the accident, and the logbook entry for that inspection indicated that the engine had accumulated less than one hour of operation since its reinstallation. At the time of the accident, the engine had accumulated .66 hours tachometer time since the annual inspection.