PA-28 instructor pilot reported returning to departure airport after the engine began running rough.

Attributes
ACN	1541030
Time
Date	201805
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	PA-28 Cherokee/Archer/Dakota/Pillan/Warrior
Operating Under FAR Part	Part 91
Flight Phase	Climb
Flight Plan	None
Component
Aircraft Component	Engine
Person 1
Function	Instructor
Qualification	Flight Crew Instrument Flight Crew Flight Instructor Flight Crew Commercial Flight Crew Multiengine
Experience	Flight Crew Last 90 Days 568 Flight Crew Total 1810 Flight Crew Type 1770
Events
Anomaly	Aircraft Equipment Problem Critical

Narrative:

At about 900 feet after takeoff; aircraft started shaking and engine was not developing full RPM. I took controls from the student; turned back towards airport and asked tower for priority handling to land on [the nearest] runway. Fuel pump was on. Tower asked if we needed assistance and I said no as we were at 1;000 feet and close to the airport. On downwind; aircraft continued shuddering and I again asked tower for priority. Tower said unable. Aircraft was still shuddering and unsure if engine was about to quit; I [advised ATC] and landed.

Original NASA ASRS Text

Title: PA-28 instructor pilot reported returning to departure airport after the engine began running rough.

Narrative: At about 900 feet after takeoff; aircraft started shaking and engine was not developing full RPM. I took controls from the student; turned back towards airport and asked Tower for priority handling to land on [the nearest] runway. Fuel pump was on. Tower asked if we needed assistance and I said no as we were at 1;000 feet and close to the airport. On downwind; aircraft continued shuddering and I again asked Tower for priority. Tower said unable. Aircraft was still shuddering and unsure if engine was about to quit; I [advised ATC] and landed.

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.