you need a scan tool to isolate the bad cylinder. once you know that...swap a plug, wire and col to a non misfiring cylinder....see if the misfire follows the parts to you moved to the new cylinder...if yes...the parts are bad. if no....do a compression test of that cylinder.

if you don't want to go that way....how old are the spark plugs...if over 100 000 change them. pull one at least to see how bad they are.