The pilot reported that, during the descent for landing, the engine did not respond when he attempted to level off and increase power. Further attempts to adjust the throttle were unsuccessful and engine rpm remained at 1,900. As the airplane was over the runway, the pilot was unable to slow it down, so he forced the nose down onto the grass that was beyond the runway end. After the airplane touched down, it bounced twice, collided with a fence, and nosed over. The airplane was substantially damaged and the pilot and passenger were unhurt. The Federal Aviation Administration inspector who responded to the scene confirmed the substantial damage and found that the connecting hardware for the linkage between the fuel injector servo and the throttle cable were missing. The missing bolt, washer, and nut were subsequently found loose, inside the engine cowling; however, the nut was inconsistent with the nut required by the aircraft illustrated parts manual. The engine had been overhauled and reinstalled about 50 operating hours before the accident.