On June 4, 1995, at 1720 hours Pacific daylight time, a Bellanca 8KCAB, N5540K, lost engine power, landed on a highway, and collided with an automobile. The airplane was being operated by Orange County Flight Center, Santa Ana, California, as an aerobatic instructional flight. The local flight originated from the John Wayne-Orange County Airport, Santa Ana, California, at 1615 hours. The airplane was substantially damaged. The certified flight instructor (CFI) and certificated commercial pilot student were not injured. The two occupants of the automobile sustained minor injuries. Visual meteorological conditions prevailed at the time of the local flight. According to the flight instructor, the airplane lost power while performing aerobatic maneuvers at 3,500 feet. The flight instructor initiated a forced landing on a paved road in Mission Viejo, California. During the landing ground roll, the airplane collided with an automobile driving on the road. After recovery from the accident site, the airplane was checked by an airframe and powerplant mechanic. According to the mechanic, no discrepancies were found with the airframe. Examination of the engine compartment revealed that the throttle linkage was disconnected from the carburetor throttle arm. The bolt was found in the throttle arm hole; however, the required castellated nut and a cotter pin were missing from the bolt. A Federal Aviation Administration Airworthiness Safety Inspector from the Long Beach Flight Standards District Office, Long Beach, California, examined the aircraft and reported the same findings as the mechanic. The aircraft maintenance records indicated that prior to May 16, 1995, the aircraft sustained a propeller strike and the engine was removed for disassembly and inspection. The engine was installed on May 22, 1995, following reassembly. The last annual inspection was performed on April 26, 1994.