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I think it would be very rare, indeed, to find a coil of wire with an intermittant connection condition. It is much more likely that there is an intermittant 'connector' or 'contact' that is linked with that coil.
First, check ALL of the other possibilities for electrical transfer. Every component that passes electricity within a relay can be suspect.
For the coil, itself, to be intermittant, the wire used to make the coil must have a complete break in it somewhere...and then some physical movement of that wire must occur which causes it to electrically "make" and "break". Extremely unusual...but not impossible.
P.S. Dirty or corroded contacts would yield the same symptoms as an "intermittant" coil.
How can you check a coil that may work intermittently?
I don't now how to check one, but they do get flaky. Mine would start missing after it got warm. Then would smooth out. Then miss at highway speeds. Drove me crazy. Not sure where I found my problem described but it said it was probably the coil. Replaced the coil and every thing was rosy.
From: Las Vegas - Just stop perpetuating myths please.
Best way i know to check a coil bad is replace it with a known good coil.
Coils are liquid filled and should be mounted upright.
U can hook up a meter and use a heat gun to heat up the coil watching for a change in resistance (or voltage if energized). Remember both the primary and secondary winding share a lead in common.
U can wiggle it or tap on it too.
I don't know what year C3 you have, or what yor symptoms are, but I had a Nova once that started to sputter and jerk during acceleration. It had an HEI system and the problem turned out to be the pick-up coil.
Since you have HEI, it's possible to have the module in the distributor going bad. It's not unusual after all these years to occur and is an easy fix if it proves to be the culprit.