Same problem here with my motorhome, got water in the gas at $3.54 per gallon with a terrible misfire, so bad, had to switch on the hazards and pull to the side of the road.
Barely made it to the next town, got a new fuel filter, and since I have an electric fuel pump in this thing, had my wife switch it on to get some good gas flow. Threw in a couple of cans of heat, and was good to go. On this thing had to crawl under, a 1982. Easier with fuel injection, and still a major problem. A net search revealed some odd 3,500 gas stations have water in the gas. Major problem is burying these things underground.
With FI, just connect a fuel pressure gauge, hot wire the fuel pump, has a side valve to drain the water out into a container, and very easy to see water in the gas.
Same with our airports around here, had to get special permission to install tanks above ground, put a double chain link fence around them and 50,000 no smoking signs.
Had a very bad misfire after taking off not once but twice in my lifetime. Both times, I broke FAA regulations, made a very careful 180 and landed the planes safely on airport grounds without crashing into someones home and getting killed myself. Ha, thought they were going to ground me, but gave me a pat on the back instead.
Coil is a very basic device, three terminals on a ferrite core, with a coil of wire around it. One to the spark plug, center tap of the coil to 12V, third to the collector of gated bipolar transistor. In theory, should last forever. Can find corroded connectors to it, or poorly soldered connectors, but gone to either spot or ultrasonic welding. Most dreaded is a shorted turn, sucks up all the spark, have a tester for this, so no whether its good or bad, plus high voltage testers.
That epoxy layer is thin, much softer material is used underneath that can be scraped away, silastic is the name. Ha, can peek inside to check the internal connections.
No more ignition modules, part of the ECU now, saves wires and money, some as high as $1,300.00, if one of the transistors is bad, just replace that, have other uses for that 1,300 bucks, like paying taxes and eating.
In 1964, cost $2.35 to make a voltage regular, electromechanical, lots of copper wire, tungsten contacts, hand assembly, galvanized base, and a painted cover with four plated brass terminals on it. And this was in 1964 money, today that voltage regulator only cost 67 cents to make, and like printing newspapers. And that is at todays dollars. Just one component in a vehicles.
Even with todays inflation, and how they are manufactured, a new car shouldn't cost anymore than it did in 1964, hearing this from a guy that knows. And sure don't have all that stainless steel and good bolts.