On September 10, 2002, at 0845 central daylight time, a Cessna T188C, N9432J, operated by Willmar Aerial Spraying Service Inc., was substantially damaged during an aborted takeoff from runway 29 (3,498 feet by 75 feet, asphalt) at Olivia Regional Airport, Olivia, Minnesota. Instrument meteorological conditions prevailed at the time of the accident. The 14 CFR Part 137 agricultural flight was not operating on a flight plan. The commercial pilot was uninjured. The local flight was originating at the time of the accident. The pilot stated that immediately after takeoff, the engine started to lose power. The engine lost 200 rpm and the pilot elected to perform an aborted takeoff. The airplane came to rest on a corn field about 1/2 mile from the departure end of runway 29. Examination of the engine by a Federal Aviation Administration revealed that the number 1 and number 3 lower spark plugs were oil filled and contained lead deposits. The oil was removed and the plugs were operationally checked under pressure. Under standard pressure, the plugs fired intermittently, and under pressure (120 psi) the plug did not fire. The plugs were then cleaned, tested, and subsequently fired under pressure.