Help with ignition problem please.

[notyo_cheez]

Always begin at the source, check for 12V feeding the coil. You have that, then ohm out the coil. If that checks, try a new cap and rotor especially if it's been awhile since they've been replaced or you have no idea how old they are. Modules will fail but not very often. As you mentioned it will only do this on occasion, best guess is that the rotor/cap may have cracks you can't see to the naked eye that will cause a wild arc. They are cheap enough to replace and it's a good start to diagnose. Pick up a fresh set of spark plug cables with the rotor and cap, and a fuel filter for good measure.