On July 3, 2000, about 1300 mountain daylight time (MDT), a Cessna 150L, N6875G, registered to and operated by Flight Quest, was substantially damaged during an off airport forced landing following a loss of engine power. The accident occurred in an open field near Nampa, Idaho. The student pilot, the sole occupant of the aircraft was uninjured. No flight plan was filed and visual meteorological conditions prevailed for the local 14CFR91 instructional flight. The flight originated from Nampa Municipal Airport (field elevation 2,573 feet above mean sea level) approximately 5 minutes prior to the accident. There was no fire and no report of ELT activation. The pilot reported that she leaned the mixture prior to takeoff. Shortly after departure, during the climb, the pilot readjusted the mixture (aft) due to poor engine performance. Shortly after readjusting the mixture, the engine began to run rough and eventually quit. The pilot initiated a forced landing to an open field near the airport. During the landing roll, the aircraft's nose gear collapsed. Substantial damage was reported to the aircraft's left wing, left aileron and firewall. At 1353 MDT, the surface observation for Caldwell, Idaho, five miles northwest of Nampa, reported winds from 310 degrees at 7 knots; temperature 22 degrees Celsius; altimeter setting 29.88 inches of mercury. The owner's manual for the aircraft (section 2) states, "Prior to take-off from fields above 5,000 feet elevation, the mixture should be leaned to give maximum RPM [rotations per minute] in a full-throttle, static run up." The density altitude at Nampa Airport, during the same timeframe as the accident, was approximately 3,890 feet.