Narrative:

This was the first checkout flight for me with an instructor working toward a sign-off allowing me flying club privileges for this aircraft. After taxi to the run up area; we smelled light odor of oil that quickly dissipated. Upon run-up we noted slight roughness on left mag that cleared up after leaning mixture at power for 30 seconds. Departure from ZZZ was normal followed by short flight through the class B airspace to ZZZ1 for some pattern work. After a stop and go; departure was a short field takeoff that was normal until about 900 feet AGL when the instructor reduced power to 25 inches which caused a sudden decrease in power and increased vibration. Since we were approaching traffic pattern altitude and still had some power output from the engine (though greatly reduced) we did not declare an emergency as we were troubleshooting the problem on downwind. Manifold pressure continued to read at or near full power even as we moved the throttle through a wide range of power settings. We kept the aircraft close to the field in anticipation of a possible complete loss of power and were high for our final approach requiring some 'south' turns to lose altitude to get back on glideslope. After touchdown; the engine continued to produce power with a higher than usual throttle setting allowing us to taxi to transient parking where we secured the aircraft. After engine shutdown; moderate smoke came out from the engine cowling. After removal of the top engine cowling we found several problems visible to two non-mechanic pilots - a loose spark plug wire to #1 cylinder; air inlet hose to the throttle body had fallen off; large amounts of motor oil in the bottom cowl and dripping onto the ground; and two cylinder stud/bolts sheared off of #1 cylinder.

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Original NASA ASRS Text

Title: PA-32 instructor and student pilot reported engine problems during their training flight. After landing they found several serious mechanical discrepancies; leading the instructor to state he felt improper maintenance was a factor.

Narrative: This was the first checkout flight for me with an instructor working toward a sign-off allowing me flying club privileges for this aircraft. After taxi to the run up area; we smelled light odor of oil that quickly dissipated. Upon run-up we noted slight roughness on left mag that cleared up after leaning mixture at power for 30 seconds. Departure from ZZZ was normal followed by short flight through the class B airspace to ZZZ1 for some pattern work. After a stop and go; departure was a short field takeoff that was normal until about 900 feet AGL when the instructor reduced power to 25 inches which caused a sudden decrease in power and increased vibration. Since we were approaching traffic pattern altitude and still had some power output from the engine (though greatly reduced) we did not declare an emergency as we were troubleshooting the problem on downwind. Manifold pressure continued to read at or near full power even as we moved the throttle through a wide range of power settings. We kept the aircraft close to the field in anticipation of a possible complete loss of power and were high for our final approach requiring some 'S' turns to lose altitude to get back on glideslope. After touchdown; the engine continued to produce power with a higher than usual throttle setting allowing us to taxi to transient parking where we secured the aircraft. After engine shutdown; moderate smoke came out from the engine cowling. After removal of the top engine cowling we found several problems visible to two non-mechanic pilots - a loose spark plug wire to #1 cylinder; air inlet hose to the throttle body had fallen off; large amounts of motor oil in the bottom cowl and dripping onto the ground; and two cylinder stud/bolts sheared off of #1 cylinder.

Data retrieved from NASA's ASRS site 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.