Marrowbone Boy

I have a problem with my 05 4.0l Ranger Edge! Slight misfire every once in a while buy at high way speeds it jumps! Going to check the plugs and wired because I just put all new in it. May be a bad wire or not plugged in good and it started the misfire at speed about 500 miles after but I added the new plugs and wired because of the mis fire at idle! Anyone with any ideas ! Engine light is on and wont go off!! Worried my ranger may have a serious problem!!! HELP!