04 Optima 4 cyl

This is wierd I have an 04 kia Optima 4 cyl with 97000. We dorve the car on Wed and it did great and then my wife got in the car and backed out of the driveway and the car started to miss ad would not go above 50 miles per hour. I got home changed the spark plugs and it is doing the same thing. I started to unplug the wires one at a time and got a poorer running car untill I unpluge the #3 cylinder wire the car ran the same. So I plugged in anotuther plug into the wire and grounded it but there was no spark on the plug. Could it be a wire or the coil. and could anyone explain to me how the coil works on this car becoase there is only 2 coils?