On May 2, 2008, about 1215 Pacific daylight time, a Cessna 175A single-engine airplane, N7059E, made a forced landing following a partial loss of engine power near Rio Linda, California. The airplane was registered to, and operated by, the pilot under the provisions of Title 14 Code of Federal Regulations Part 91. The private pilot and passenger/owner of the airplane were not injured; the airplane sustained substantial damage. Visual meteorological conditions prevailed, and no flight plan had been filed for the personal flight. The cross-country flight originated from Rio Linda about 35 minutes prior to the accident with an intended destination of Medford, Oregon. The owner of the airplane reported that he had recently purchased the airplane, and was moving the airplane to his home field. The pilot and owner departed from Rio Linda and climbed to an altitude of 1,500 feet mean sea level (msl). About 20 to 30 minutes after departure, the engine began losing power followed by several backfires. The pilot reported that he observed blue smoke originating from the engine cowling, and noted that the engine revolutions per minute (rpm) was reduced to about 1,500 to 2,000 rpm. The pilot stated that he was unable to maintain altitude at the reduced power setting, and initiated a forced landing to a gravel road. During the landing roll, the left and right wings struck trees located on the edge of the gravel road. Examination of the airplane by the pilot revealed that the left and right wings were structurally damaged. During a telephone conversation, the owner of the airplane reported that during disassembly of the engine, the number four cylinder exhibited "signs of detonation." The number four piston head was "eaten away" to the top ring land. No additional anomalies were noted with the engine. The reason for the detonation was undetermined.