"check Engine" Misfiring cylinder

I have 96 HSE 4.6 Range Rover which is new to me and it is showing "Check Engine"light. Code reader indicates the source is misfiring cylinder. I have changed plugs and plug wires all look great. Still have engine light and so I pulled the new plugs and checked them again and all indicate that they are firing. How can I isolate the cause of the Check Engine light? bad cylinder, bad sensor, I'm willing and capable of doing the work I'm just not sure which way to proceed. Any assistance will be appreciated. Bob Mc