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I have honestly never tested one. I had a few spares laying around from trips to the junkyard (what fits in your pocket is free LOL). But I was very familiar with the symptoms. Car would start fine when cold, then die when it approached operating temperature. And would not restart until it cooled back down. I've owned several Preludes over the years, and that was a very consistent symptom. I'm not saying there can't be other symptoms, but each time I had that symptom, replacing the ignitor solved the problem.

So I did as in the video I posted, and it worked perfectly. The plug for the ignitor above the signal lead (two white leads) is open, so you can just stick a wire through it and bend it down to the white leads. Then plug it back in and you are all set up. I then hooked up a little 12v LED I bought from Home depot between the wire and the positive lead, turn the car over, and you can see the ECU trying to talk to the ignitor, and ignitor ghosting the ECU. The coil and spark plug wires check out, so it has to be the ignitor.

It seems like a more straightforward way to determine whether the ignitor is bad than what they tell you to do in the book. It's a shame they didn't include it. Now that I rack my brain, I think I never replaced it because I could never tell definitively whether it was broken, and I didn't want to guess and buy a $100+ part that might be fine. I would just replace a cap or a coil or something, and it would start working again...until it didn't. The symptoms you are describing are pretty similar, but mine reaches these periods where it won't even start cold, and then one day, after a lot of screwing around with parts, it starts working again.

 

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These symptoms certainly sound like igniter failure. Most often we see igniters fail because something else in the system is worn, causing more stress on the coil, and in turn, igniter.

OK, I believe you, because here is what is happening. I replaced the igniter, and it worked perfectly for about three weeks, without running it much. I ran it maybe 5 times sitting in the garage to work on other stuff. I then let it sit for about 2 weeks while I was away. I just tried to start it up again, and no spark.

This is not the first time I have been through this cycle. It has done this to me at least 5 times, where I get no spark, I replace some component in the ignition system, and it works right away, and then it sits for a while, and while it is sitting, something breaks again.

The first time, I replaced the distributer cap and rotor, it worked fine.
It happened a second time, I replaced the cap and rotor again, fixed right away.
I replaced the ignition coil the third time it happened, fired right up.
Fourth time it happened, I had it at a mechanic, and he called me and told me my ignition coil is shot. He replaced it and it was fixed.
See the fifth time detailed above, changed the igniter, worked perfectly.

Now it is doing it again. Last time I ran it, it was fine. I just went out to test drive it around the block (sat for two weeks, battery still has juice, no other weirdness) and no spark.

What is the thing in this car that could be killing my ignition components when it is just sitting in the garage? Should I be looking at the alternator, main fuse, ignition switch? I've check them all by the book, and they seem fine.

 

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I had the idea to install a breaker or fuse (preferably breaker) to protect the igniter unit while I am figuring out what is wrong. Based on the schematic in the first post, where do you think I should install this and what rating do you think I should use? If I had to guess, I would say the Blk/Yel wire since that seems to be the power supply.