On August 31, 2002, about 1025 Pacific daylight time, an Ercoupe 415-C, N87204, made an off airport landing following a loss of engine power about 5 miles southeast of Fresno, California. The owner was operating the airplane under the provisions of 14 CFR Part 91. The private pilot was not injured, and one passenger sustained minor injuries. The airplane sustained substantial damage. The personal local flight departed Chandler Airport (CHD) in Fresno about 1015. Day visual meteorological conditions prevailed, and no flight plan had been filed. The pilot stated that an annual inspection had just been completed on the airplane, and he was taking the owner up to check the airplane out. They added about 10 gallons of gasoline to the airplane and departed. They were returning to CHD, and the engine began to run rough and lose power. They decided to land on a road. The touchdown was on the road's centerline. However, the left wing hit a pole, and the airplane began to weave. The airplane hit another pole and departed the road into soft dirt. The main landing gear dug into the soft dirt, and the prop nosed into the ground. Both wings and the fuselage sustained substantial damage. A Federal Aviation Administration (FAA) airworthiness inspector supervised the examination of the engine. The fuel screens were clean and the carburetor box was clear. Fuel was present in the carburetor bowl. Maintenance technicians removed the top spark plugs from each cylinder. All gaps were similar and none of the plugs exhibited any mechanical damage. Technicians rotated the engine and obtained spark from each magneto in firing order. The accessory gears turned freely. None of the valves or cylinders exhibited internal mechanical damage. They rotated the engine, and the valves moved in firing order with the same amount of relative lift. The fuel lines were clear; no contamination was present. Technicians supplied a temporary fuel supply to the right wing supply line. The engine successfully ran smoothly to 2,000 rpm. It was not prudent to run at a higher rpm due to prop and nose gear damage.