The pilot was preparing the aircraft for a local flight. The weather was fine and the ground surfaces were dry. He moved the aircraft out of its hangar onto an adjacent taxiway and attempted to start the engine. The start was not successful so, before attempting a second, he advanced the throttle. The subsequent start was successful but the engine immediately produced high power, and the aircraft began to move forward and to the right. The pilot was unable to stop the aircraft before it had travelled approximately 30 ft and collided with a parked, unoccupied private vehicle. Both the aircraft and the vehicle sustained damage but the pilot was uninjured. He attributed the high power setting on start to the throttle position, which was more advanced than he had intended.