Like Tome said, but also check the electrical wires coming off the Coil plug. They break in the insulation and you would never see it. This happens because as soon as they come out of the plug, they bend to meet up with the main harness.
1994 Chevrolet Caprice Classic Woody Wagon. (My toy)
2014 Chevrolet Silverado 2WD 2WT RCSB 4.3 ALLOY V6 (My daily)
1994 BMW 325i Cabriolet 2.5 I6 (My flip car that turned into wife's toy)
2007 Pontiac G6 VL 2.4 I4 (Wife's Daily)