As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING FLIGHT, THE PILOTS NOTED THAT WHEN THE THROTTLE WAS BROUGHT TO LOW POWER/IDLE, IT WOULD BECOME STUCK AND THEY WOULD HAVE TO FORCE OR JIGGLE THE THROTTLE UNTIL IT OPENED. THEY ELECTED TO RETURN TO BASE. INSPECTION REVEALED THE CARBURETOR WAS STICKING WHEN THE THROTTLE WAS CLOSED OR CLOSE TO CLOSED. THE STICKING APPEARS TO BE COMING FROM THE ACCELERATOR PUMP.