On July 25, 2011, about 1130 central daylight time, an Evens RV-4, N20JE, sustained substantial damage when it impacted terrain during a forced landing to a field near Monroe City, Missouri. The airline transport pilot was uninjured. Visual meteorological conditions prevailed at the time of the accident. The 14 Code of Federal Regulations Part 91 personal flight was not operating on a flight plan. The flight originated from Eagle's Nest Estates Airport (2TS6), Midlothian, Texas, about 0820, and was en route to Capt. Ben Smith Airfield, Monroe City, Missouri. The pilot stated that before the airplane descended to an intermediate cruise altitude, he selected carburetor heat and noted a normal decrease in engine speed. He then deselected carburetor heat and descended to 5,500 feet mean sea level. About 20 minutes after the descent, the engine experienced three instances where it ran rough with a corresponding loss of engine power. The pilot was unable to regain engine power by changing fuel tanks. During the approach to the destination airport, the airplane experienced a total loss of engine power, and the pilot performed a forced landing to a corn field. The airplane sustained substantial damage to engine firewall. A postaccident examination of the airplane revealed no anomalies that would have resulted in a loss of engine power. According to a Federal Aviation Administration Carburetor Icing Probability Chart, a probability of carburetor icing existed at glide power at the conditions reported by the Quincy Regional Airport-Baldwin Field (UIN), Quincy, Illinois, automated surface observing system (ASOS). The ASOS was located about 31 nautical miles northeast of the accident site and at an elevation of 769 feet mean sea level. The UIN ASOS recorded at 1054: temperature - 86 degrees Fahrenheit, dew point - 75 degrees Fahrenheit.