Engine suddenly started misfiring. Changed plugs, wires, fuel filter

I have 3 vehicles of my own and they all began acting up this week, Bad luck!!..I pull the wires from the coil one by one slowly but did not notice any change in engine , still had slight miss ideling. I may change coil next.

Don't do it if it's not bad, pull the wire completely away from the tower, away from the spark, and make sure the tower sparks back against itself on each tower. If there wasn't a change in the engine, you must be getting fire from somewhere else. It has to change if you cut the spark off to the plug. Check it again, use some plastic, like I have plastic pliers, you need to insulate yourself from the spark.