Skyhawk 172/Cutlass 172
Flight Crew Commercial; Flight Crew Flight Instructor
Situational Awareness
Aircraft Equipment Problem Less Severe
Flight Crew Diverted; Flight Crew Took Evasive Action; General Maintenance Action
Aircraft
I initiated an engine failure on my student at 4500 feet and had him steep spiral down. Upon reaching 1500 feet AGL he recovered from four rotations and began to configure the aircraft for the simulated engine failure power off landing. Upon reaching 550 feet AGL he initiated a go around adding full power immediately. On climb out a very strong engine vibration began and we lost much of our available power. I turned carb heat back on in the event it was icing but it didn't correct the engine vibration. I then adjusted mixture leaning it out and pulled power to idle then firewalled it at which point power slowly came back. I then diverted to the nearest airport with services and informed operations and had maintenance inspect the aircraft. It was determined that a fouled plug was most likely the cause and after a run up the aircraft was flown back to [home airport]. No further incident occurred.
C172 flight instructor reported a loss of engine power during a go-around from a simulated engine failure maneuver. After diverting; Maintenance concluded that a fouled spark plug was the likely cause.