On May 21, 2005, approximately 1250 mountain daylight time, a North American Navion, N8874H, collided with a pole during an attempted forced landing near the edge of a golf course near Emmett, Idaho. The private pilot was not injured, his passenger received a minor injury, and the aircraft, which is owned and operated by the pilot, sustained substantial damage. The 14 CFR Part 91 personal pleasure flight, which departed McCall, Idaho, about 45 minutes prior to the accident, was being operated in visual meteorological conditions. No flight plan had been filed. There was no report of an ELT activation. According to the pilot, during cruise flight the engine experienced a partial loss of power, and although there was some power being produced by the engine, it was not enough to maintain level flight. The pilot therefore turned on the fuel boost pump and switched tanks, but the situation did not change. He therefore started looking for a place to make an emergency landing. The first place he headed for had people and equipment near the end of the landing area. He therefore headed toward what appeared to be an open field, but as he got closer he could see that there were sprinkler pipes across the area. He therefore attempted to glide to a nearby golf course, but he came up just short and touched down at the end of a street just outside of the golf course boundaries. Just as the aircraft was touching down, it impacted a light pole and then slid onto the golf course property. Except for the fact that there was an air-space at the top of the gascolator, the post-accident inspection of the engine did not find any anomalies that would be expected to contribute to a partial loss of power, but due to a history of accidents caused by faulty Navion fuel selector valves (addressed in Navion Service Bulletin No. 101), the fuel valve was removed from the aircraft and shipped to the custody of the FAA for further testing and inspection at Sierra Hotel Aero, located in South Saint Paul, Minnesota. This inspection revealed that the valve showed evidence of fuel/air leakage at the top of the stem, and upon disassembly was determined to contain a worn valve stem and a hardened and brittle O-ring. It was the determination of the inspection team that the siphoning of air into the fuel system through the worn stem and hardened O-ring most likely would have lead to a partial loss of engine power. According to the inspection team, the problems associated with the selector valve where the result of age (the O-ring) and normal wear-and-tear (the stem).