tell me what this cel means

[chaos02001]

my cel was on so I used my pocketlogger to find out what was causing this and it says ( misfire in cylinder #4 ) my car is also making a knocking sound very inconsistant knock have no clue what it is any help would be more than helpful the knock is loud then quite and really is inconsitant as revs fluctuate the cel came on then shortly after that the knock started it will still drive but sometimes wants to die please help!

 

[twenty5psi]

a misfire can be a bad wire or plug..check your plug out in that cylinder and see if its gapped right or if its basicaly burnt out..check the wire to that cylinder too for arcing..