A resistance check will not show up a high voltage pathway between the primary and secondary windings. It's basically a hole in the insulation that allows a spark to jump beteween the two windings. Early HEI systems for the odd-fire Buick V6 were notorious for burning a hole in the distributor cap under one of the coil attaching screws and making one cylinder miss intermittently. It was impossible to duplicate on a scope unless the car was on a chassis dyno so the engine could be loaded in the shop. The repeated flashover would cause frequent failures of HEI ignition modules. GM solved the problem by making the cap thicker in the area that was prone to burn-through. One cause of burn through on a conventional coil is a dangling plug wire that allows the secondary voltage to go to 25-30 KV or more without firing a plug.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!