Flight Crew Commercial; Flight Crew Flight Instructor
Flight Crew Last 90 Days 41; Flight Crew Total 610
Aircraft Equipment Problem Less Severe
Flight Crew Diverted
Aircraft
Took student to practice area. After steep turns we configured for slow flight. Student reported that he couldn't retard power any more for the maneuver. I took command of the airplane and could advance throttle but not pull back to idle at all. It was catching on something. At this point I could force it but what if it broke. I immediately headed towards ZZZ. Along the way I tried to baby it back but nothing. So knew I would have to set up for a power off landing. With ZZZ being 3800 ft runway and now with a REAL world situation I knew it had to be perfect for a zero overrun. With that in mind I decided to [advise] and head to ZZZ1. I called tower and did thus so. Abeam the numbers I cut the mixture and cut mags and did a successful landing.
PA-28 flight instructor reported a throttle malfunction that prevented the power from being reduced.