Narrative:

Upon takeoff everything was normal; however I felt that the throttle lever was pushing back out. I tightened the throttle friction lock. The plane performed well as expected. When I reached my cruise altitude I noticed that when removing power to cruise power setting that a great amount of throttle removed on the lever was only amounting to a very small change in manifold pressure (1/3 of the travel only produced 3-4 mp decrease). At this point I was thinking that we were having some trouble so we decided to continue on to ZZZ; a few miles away. We positioned over the airport and started to remove power and there was no response other than a slight decrease in mp. After slipping in a descent I put the landing gear down and pulled the power on final approach and glided into the airport. Everything was fine; we restarted the engine to taxi and immediately it went to full power. So we taxied it in and parked the plane. I believe there was a problem with the throttle cable which may have caused the carburetor butterfly to engage full throttle as a protective measure. Our mechanic will be looking at it shortly to determine the cause. The only way I could have been more proactive would have been to take off the cowl during my preflight; perhaps the problem could have been visually seen. The cowl which has many many screws is not easy to take off and I did look in the engine compartment and checked oil before flight; however you can't really see the carburetor.

Related reports:

Google
 

Original NASA ASRS Text

Title: M20 pilot reports throttle linkage failure with throttle fixed at high power setting. When landing is assured engine is shut down with mixture control. Safe landing ensues.

Narrative: Upon takeoff everything was normal; however I felt that the throttle lever was pushing back out. I tightened the throttle friction lock. The plane performed well as expected. When I reached my cruise altitude I noticed that when removing power to cruise power setting that a great amount of throttle removed on the lever was only amounting to a very small change in manifold pressure (1/3 of the travel only produced 3-4 MP decrease). At this point I was thinking that we were having some trouble so we decided to continue on to ZZZ; a few miles away. We positioned over the airport and started to remove power and there was no response other than a slight decrease in MP. After slipping in a descent I put the landing gear down and pulled the power on final approach and glided into the airport. Everything was fine; we restarted the engine to taxi and immediately it went to full power. So we taxied it in and parked the plane. I believe there was a problem with the throttle cable which may have caused the carburetor butterfly to engage full throttle as a protective measure. Our Mechanic will be looking at it shortly to determine the cause. The only way I could have been more proactive would have been to take off the cowl during my preflight; perhaps the problem could have been visually seen. The cowl which has many many screws is not easy to take off and I did look in the engine compartment and checked oil before flight; however you can't really see the carburetor.

Data retrieved from NASA's ASRS site as of April 2012 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.