As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
MIXTURE ARM ADJUSTMENT RETAINING SPRING BROKEN DUE TO ATTACHMENT END BEING WORN. WHEN SPRING BROKE, IT ALLOWED MIXTURE SETTING TO CHANGE WHICH CAUSED ENGINE TO RUN ROUGH AND LOST POWER. SUBMITTER RECOMMENDED A MORE SUBSTANTIAL SPRING THAT IS LESS SUSCEPTIBLE TO WEAR OR TO PROVIDE A MEANS OF SAFETYTING THE ADJUSTMENT ONCE THE PROPER MIXTURE SETTING IS OBTAINED AND IS MADE AVAILABLE.