Ignition Coils

if it has a noticeable miss that you can feel or hear , you can use insulated pliers , and pull one wire at a time and see which one makes no difference , a scan good tool would reveal this problem , you would be able to see the cylinders firing and fords wds can do a stress test on the coils ,
caution when pulling plug wires , dont touch metal , and use the right pliers , coil spark may not seem like much but it does sting pretty good

if i'am not misstaken each cyclinder has a coil over each plug. a lot of times moisture will collect inside the holes where the plug boots are and will cause crossfireing in the hole only way i know to check them is to pull each one and check for moisture if engine has been washed at anytime that is a sure fired way to get moisture.NOS 8)