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Discussion Starter · #1 ·
Hi,

I'm looking for an appropriate way to test my igniter unit. I found this online (Link) and was wondering if there was a similar approach with our cars (I have an 89 SI).

Little background, I've had off and on issues with hard starts, stalling, misfiring, and periods where I can't start the car. Everytime, the cause of this is no spark. Usually, I can replace something, and it will start working again for a period of time. For instance, I recently had a mechanic replace the intake manifold gasket, and he told me my coil was bad, causing the rough starts. He replaced it, it worked for a while, but now the problem is back. In the past I've gone through this cycle, and temporarily fixed the issue by changing the distributer cap a few times, changing the coil once or twice, etc. I think I'm just getting lucky (or unlucky) and have never found the true cause, which brings me to the igniter unit. I've worked through the troubleshooting steps in the manual. I've tested the ignition switch (good), current spark plug wires (good), and the current coil (good). I've also swapped out the ECU and haven't noticed any change. I notice that the igniter unit is getting power (I see battery voltage at the blue and blue/yellow wires in the diagram below when the key is in the start position).

The troubleshooting steps for the igniter, unfortunately, start with a code 15. My car is not throwing this code. The other problem is that you never check the igniter directly, just everything around it. If I go through everything in the tree (omitting the ECU checks since I don't have a ECU checker wire), I don't find any issue with anything else, indicating that the igniter is bad, but I haven't really checked it.

Does anyone know a good way of checking this unit directly? Or, does anyone know how best to check the signal from ECU? Should I be looking into sensors that may be able to interrupt the igniter signal, such as the crank/TDC sensors?

Sorry, it's a bit scatterbrain, but I'm kind of lost in wiring diagrams right now. Any suggestions are very appritiated.

29510
 

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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.
 

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Discussion Starter · #3 ·
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.
 
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