I need some insight on specifically what happens at the plug when the gaps cannot be fired for any reason such as a very lean misture, excessive gap or a short.
The plugs have center electrode resistance anywhere from 500 to 5000 ohms.
Does the spark attempt to find ground to the shell in these cases, causing random missfires?
How does the voltage drop accross the resistance affect the outcome?
In the specific situation the coil is right on top of the plug by spring connection inside a rubber boot.
The coil resistance is 7000 ohms, the plugs are in the 3000 ohm range.
I am trying to track down the reason for random light load missfires that go away with a plug changes but return in a short time and go away again with another new set of plugs.
This last set was selected for lower center electrode resistance and still in testing stages.
If the missing returns, I am next going to replace the boots.
It may be the boots have grown in size and donot fit the plugs tight. As soon as the dielectric grease dries hard the leakage begins.
The coils may be pretty hot for voltage.

>>>>>>>>>>>>>>>>>>>filter

My operating hypothesis, okay w.a.guess, is that continued operation on the second set of plugs trashed the coils.  

As in, the plugs' effective resistance went way up, for whatever reason.  When the coil field collapses, the stored energy is going to go _somewhere_.  If the plug resistance is too high, the energy will find a pinhole in the coil wire insulation and arc to the nearest ground, probably within the coil assembly.  The insulation's decomposition products include carbon, so arcing becomes more likely on future cycles.  

You might be able to partly repair the coils by vacuum impregnating them with green Loctite  (#271 ?), the wicking kind that's used for sealing porosity in castings.  Probably not.

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