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secondary ignitio waveform interpretation -help

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28 Aug 2019 21:56 #33241 by josegumby
2001 honda civic hx vtec engine.
Hi - DIYer here. I've been watching all the scannerdanner videos for a couple years now. and ive developed a habit of buying expensive diagnostic tools (dont tell my wife).

So my wife's 2001 civic FINALLY has a problem and now I can put some of what I learned to use. Attached is a current and secondary voltage of all 4 coils, triggered on cyl 1. Firing order is 1-3-4-2. So right away I see a problem with cylinder 4 with both voltage and current waveforms. Looks like good control and based on current, power and grounds appear ok. so I replaced cop 4 and car is running fine now.

my question - what in the world is going on with cyl 3 and 4 after the repair. the voltage waveforms look very different than 1 and 2, although the car seems to run fine. I suspect it needs new spark plugs since the car has over 225000 miles on it. But I'm actaully more interested in the interpretation and theory behind why they look so different. especially from someone that has a bit more experience looking at ignition waveforms than I do.

Thanks!!
Curt

ps. I didnt think to do a throttle snap till after I had everything put away. :(

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28 Aug 2019 22:46 #33242 by Tyler
Which COP pickups were you using at each coil, specifically? Or were you using extension leads and clamps?

It almost looks like the pickups at cylinder #1 and #2 were making good contact, but cylinder #3 and #4 weren't placed quite as well? #2 shows the best coil oscillations at the end of the burn line, while #1 kinda shows some detail during the burn line. The dwell section is missing from #3 and #4 completely.

I see this kind of thing regularly while using various ignition probes, and adjusting the probe almost always fixes it.

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29 Aug 2019 06:32 #33246 by josegumby
Replied by josegumby on topic secondary ignitio waveform interpretation -help
Hi, thank for the reply. I was using the HT extension leads with the pico mixmaster pp361. I double checked to make sure the extension leads were in all the way, and tried repositioning the clamps I will try again this weekend and test switching components around (maybe I have a couple of faulty wxtension leads or something), and also take a look at the spark plugs and probably replace them just because of the mileage.

Thanks,
Curt
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31 Aug 2019 15:23 #33322 by josegumby
Replied by josegumby on topic secondary ignitio waveform interpretation -help
Just a quick follow up. I replaced the spark plugs, and it didn't improve the wavefrom when connected to the pico mixmaster with HT extenstion leads. I don't feel bad though, as they were relatively inexpensive, and I truly cannot remember the last time they were changed. The old plugs looked rough, but the gap was perfect.

Using the PP357 COP probe, I was able to get a much clearer picture of the dwell and turn-off oscillations. The AES paddle-probe, and the Wyze-probe returned similar good results. The coils secondary waveforms for Cylinders 3 and 4 are still noticeably different from 1 and 2, but the dwell and oscillations ARE there. I have replaced some of the coils in the past, way back when I only knew how to diagnose using scan codes. So it's possible that aftermarket coils are just insulated differently, so I'm not seeing as clear of a picture.

They only mystery to me is why the whole setup with the Pico Mixmaster cannot seem to see the dwell and turn-off oscillataions as well as just about any other COP adapter. Distance from the coil, possibly (on the HT extenstion leads)???

Attached are the new waveforms using the COP probes (without HT extension leads).

Thanks!
Curt
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31 Aug 2019 15:26 #33324 by josegumby
Replied by josegumby on topic secondary ignitio waveform interpretation -help
PS - I just noticed the downward slope on each sparkline. Is that indicative of the age of the engine (ie. low compression)?

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01 Sep 2019 09:19 #33338 by Tyler
I don't know if it's the Mixmasters fault? I suspect it's just a function of the HT extensions. :silly: I've never had great luck using them.

The age and brand of the ignition coil can definitely make a difference to the waveform you see. The #2 coil in my Scion got replaced recently, and the difference between it and the OE coils is stark. If the engine wasn't running smoothly, you'd think it's misfiring. :lol:

The downward slope of the burn line and the upward slope of the dwell is pretty typical of the secondary ignition 'paddle probes', in my experience. I'm kinda surprised you got the kind of detail you did? I own that same Pico COP probe, and I've never been able to get decent readings out of Honda coils...

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01 Sep 2019 09:36 #33340 by Tyler
Here's the best I could get out of my Toyota coil with the Pico probe. Same slope to the dwell and burn lines.

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01 Sep 2019 13:39 #33346 by josegumby
Replied by josegumby on topic secondary ignitio waveform interpretation -help
Thanks! I'm checking compression on the civic now using a crappy tester whose check valve doesn't seem to be working. Best I can tell is it's getting around 160ish psi. Which , without checking Mitchell, think is pretty good.

Now I know not to read too much into that downward slope. I'll chalk it up to lack of experience.

I couldn't get a good secondary coil reading from element either. So maybe they just didn't insulate them as well back in 2001. I did use a filter and blow it up vertically with the pico. Can't quite remember the name of that setting, but I'll grab a print-screen later. I might retry the same thing on my element too at some later point.

Thanks for all your help, Tyler!

Curt

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