had a mate just call me saying his ford ka is missfiring, any other hidden things on these that would cause it to missfire apart from -

idle valve, dirty throttle body, coil pack, split ht leads, spark plugs, blocked fuel filter, temp senders?

 

normally ht lead/plug on cylinder 4 if not more than likely coil pack funked

 

Had the coil pack go twice on our one, causing your described issue