Lycoming IO-540 rough engine
I am flying a PA32-300 with a Lycoming IO-540 that gets rough engine when leaning.
The engine runs properly on the ground during taxi and engine run-up, however when cruising and setting the cruise power with the proper leaning, the engine gets really rough. If I am doing a 65% cruise and even If I lean the mixture to the 75% cruise range, it still gets rough. For example, for a 65% cruise the fuel flow should be 15GPH, but the engine starts to get rough even at 20GPH. It goes normally only above 22GPH. The cylinder compressions were tested and the injection system replaced, but the problem continues. Any idea on what this could be?