What would cause my 2002 Ford Explorer to miss while at an idle

Runs good off idle the chains and tune up did not resolve the problem, am thinking maybe the coil pack is bad have been told that fords go thru them

No done the chains first then the garage found the misfire on cyclinder 5 then they changed plugs with no resolution to the problem, I changed the wires the same day the plugs were changed, the garage was just throwing parts on it and not really trying to fix the problem. The reason the timing chains were done was you could hear them rattle and they said after they replaced the chains that it was giving a cyclnder 5 misfire. I have drove this vehicle several times since the chains were replaced and have not had a check enginge or service engine soon light come on. Like I said it only does it on idle while stopped, rpms around 100 to 300 rpms at idle

Do not know if the shop did a compression test, all I know is that they replaced the plugs said they were gapped to far so that is why I was thinking coil pac, or maybe the IAC is not operating or the MAF needs cleaned where should I start

What would be a good cleaner to use and I will pos tto let you know if it fixed the problem

Another question if I had a valve bad would I not feel it miss while I drove it or just in the idle? Will go tomorrow and pick up the cleaner and see if that works thanks you have been a great help