What happened
The pilot was conducting a maneuver involving a simulated emergency landing approach. During the procedure, the pilot applied carburetor heat and cleared the engine. The maneuver was terminated at 300 feet above ground level (agl).
Upon advancing the throttle, the pilot noted a lack of response for a short period, followed by a halting or missing response characterized by a hesitating acceleration. At approximately 200 feet agl, the pilot decided to land the aircraft to inspect the fuel and engine. The airplane touched down at 65 mph. Due to vegetation that was taller than the pilot had perceived, the aircraft decelerated rapidly and nosed over. The pilot was not injured.