As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) THE AIRCRAFT ENGINE RAN ROUGH ON RUN-UPS. INVESTIGATION FOUND THE SPRING BETWEEN THE MIXTURE AND THROTTLE CONTROL ARM WAS BROKEN/DISLODGED. THE SPRING WAS REPLACED, BUT SHORTLY AFTER BECAME DISLODGED. THE CONTINENTAL TECH REP WAS CONTACTED AND HE ADIVSED THAT THE HOLE WHERE THE SPRING FITS INTO BE CHAMFERED. A SLIGHT CHAMFER WAS MADE AND THE SPRING WAS SECURED.