Narrative:

I departed VFR over the foothills. I leveled off and pulled back on the throttle for cruise. The engine kept on running at full power. It dawned on me that the throttle was stuck wide open. I checked the propeller and mixture controls; and both were working. I figured that the best bet would be to return to the ZZZ area and set up for a power-off landing at either ZZZ or ZZZ2. I opted for ZZZ due to the longer runway and emergency services on site. After informing approach that I had an emergency condition that would require a landing without engine power; I requested and was cleared to land on ZZZ runway 12R. On downwind abeam the numbers; I pulled the mixture to the cutoff position and made a normal landing. The cause of the incident was that the throttle cable detached from the throttle linkage. The nut holding them together had vibrated off. The engine had been reinstalled on the airplane 8 days earlier following a major overhaul. The mechanic who performed the installation assures me that a cotter pin was installed on the throttle cable nut. I know this is true; since I looked over the engine carefully when I test-flew the airplane 2 days earlier. I do not know what happened to the cotter pin. On the whole; I am pleased at the outcome of this event. Between the help offered by the controllers and ZZZ personnel and the engine-out training imparted by my instructors; I was able to resolve the situation quickly and successfully. The airplane was repaired the next day and is flying once again.

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Original NASA ASRS Text

Title: M20 HAS THROTTLE LINKAGE FAILURE DURING CLB AND DIVERTS TO ARPT WITH LONG RWY FOR POWER OFF LANDING.

Narrative: I DEPARTED VFR OVER THE FOOTHILLS. I LEVELED OFF AND PULLED BACK ON THE THROTTLE FOR CRUISE. THE ENG KEPT ON RUNNING AT FULL PWR. IT DAWNED ON ME THAT THE THROTTLE WAS STUCK WIDE OPEN. I CHKED THE PROP AND MIXTURE CTLS; AND BOTH WERE WORKING. I FIGURED THAT THE BEST BET WOULD BE TO RETURN TO THE ZZZ AREA AND SET UP FOR A PWR-OFF LNDG AT EITHER ZZZ OR ZZZ2. I OPTED FOR ZZZ DUE TO THE LONGER RWY AND EMER SVCS ON SITE. AFTER INFORMING APCH THAT I HAD AN EMER CONDITION THAT WOULD REQUIRE A LNDG WITHOUT ENG PWR; I REQUESTED AND WAS CLRED TO LAND ON ZZZ RWY 12R. ON DOWNWIND ABEAM THE NUMBERS; I PULLED THE MIXTURE TO THE CUTOFF POS AND MADE A NORMAL LNDG. THE CAUSE OF THE INCIDENT WAS THAT THE THROTTLE CABLE DETACHED FROM THE THROTTLE LINKAGE. THE NUT HOLDING THEM TOGETHER HAD VIBRATED OFF. THE ENG HAD BEEN REINSTALLED ON THE AIRPLANE 8 DAYS EARLIER FOLLOWING A MAJOR OVERHAUL. THE MECH WHO PERFORMED THE INSTALLATION ASSURES ME THAT A COTTER PIN WAS INSTALLED ON THE THROTTLE CABLE NUT. I KNOW THIS IS TRUE; SINCE I LOOKED OVER THE ENG CAREFULLY WHEN I TEST-FLEW THE AIRPLANE 2 DAYS EARLIER. I DO NOT KNOW WHAT HAPPENED TO THE COTTER PIN. ON THE WHOLE; I AM PLEASED AT THE OUTCOME OF THIS EVENT. BTWN THE HELP OFFERED BY THE CTLRS AND ZZZ PERSONNEL AND THE ENG-OUT TRAINING IMPARTED BY MY INSTRUCTORS; I WAS ABLE TO RESOLVE THE SIT QUICKLY AND SUCCESSFULLY. THE AIRPLANE WAS REPAIRED THE NEXT DAY AND IS FLYING ONCE AGAIN.

Data retrieved from NASA's ASRS site as of January 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.