NOSHER

HI, I AM NEW TO THE FORUMS MY QUESTION IS... My XJ 600N SEEMS TO BE RUNNING ON 3 CYLINDERS... SPARK PLUGS ARE NEW AND HAVE BEEN ROTATED SO IT IS NOT THESE, ALSO TRIED ROTATING THE SPARK PLUG CAPS AND STILL RUNS THE SAME. DO YOU THINK ITS THE IGNITION COILS???? THANKS FOR YOUR HELP!