In an attempt to answer your question of how an ignition coil works is somewhat technical but it is a very simplistic device.

First, there are no moving parts and its one reason its so reliable.
Second, You have to get into the notion that magnetism is electricity and vice versa! The movement of energy can travel within solids and across air gaps, small and large depending on its, potential force, we call voltage.
The term current, is relative to the amount of energy, measured in amperes, is like a gallon of gas!


The term coil is the name derived from it basic form of very many turns of wire.
It is made up of two coils of wire wound in very close proximity of each other but with that air gap mentioned before.

One set of coiled wire is named the primary input coil.
The next set is called of course the secondary coil and is an output coil. This one has your distributors center terminal attached on the end of it.

What happens is current is sent to the primary coil by the way of the electronic switches of the ICU and the ignition amplifier at about battery system voltage 12 volts in pluses of on or off.

This pluse of energy/current stores itself up in one coil and it just sits there until it is turned off and the flow stops. This is where electricity turns "magically into magnetism" but moves like electricity like it started out.
The energy captured is in limbo, it cannot back out as fast as it got into the coil and so it leaps into the other nearby empty coil that has more even more finer turns of wire and for that reason can accept the energy. It gets crammed onto/into those windings which concentrates the power and transforms into a higher potential (voltage) energy of "almost" the same wattage as it first came into that first coil.

Here is where we find that "almost" is not ALL! It is call efficiency loss! It is heat or energy loss!
This is why ignition coils, transformers and alike all get hot.

Heat is an enemy of wire coils and heat is self destructive to a coil of wire or movement of magnetic energy.
Measures are taken to keep the coils within an acceptable operating range so energy will flow at an acceptable rate. These are air, oil and various coolants from gases to liquified gases.
MRI's would not be possible if it were not for copper tube conductors cut with fins surrounded in fiberglass sleeves and flooded with liquid nitrogen. I know, I prototyped some of the first ones for GE back in the early eighties. Monster machines compared to ones of today.

Heat impairs current flow and breaks down insulation of wires within coils and electricity has a basted habit of being lazy. It takes the shortest path of least resistance.... a short cut.
If it is allowed to do that then the energy does not build up correctly and go where it is supposed too!

It is this "phenomenon" that has been "theorized" into your car "failing procedure" as it is slowly loosing power until it quits. The cycle of it cooling until things start jumping back to normal until and it does it again, someday?

Again, they are very reliable item but time, the heat cycles and of course age accumulate. Ask any human, except a very young person! (:-)

A coil can fail from bad wire, insulation of the coils or incomplete cooling.
These automotive ignition coils are filled with oil or a tar like substance. Anything that a manufacturer can find to control heat and of course keep cost down. In the case of racing to make you think their coils are worth more money they will make them look real pretty on the outside too! Just kidding!

I hope this spurs your learning juices even more.
It really is not that hard to learn car stuff. It's like eating a chocolate bar, you keep breaking it into pieces just big enough to keep it tasty!

Phil