1991 Nissan Sentra Engine miss

Hello, I have replaced plugs, wires, cap and rotor button, but the engine is still idling rough and is down on power. It seems to be in the #2 cyl, when you pull the plug wire off the engine does not change, however you can hear the plug firing. The motor starts great and there are no sounds or knocks in the engine, just a miss. Any help would be GREATLY appreciated as this just happened all at once. Thanks