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Interpretting Primary vs. Secondary Waveforms on a distributor

  • SailorBob
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24 Jan 2018 08:59 - 24 Jan 2018 09:01 #17241 by SailorBob
I've got a 99 Nissan Almera 1.6L ( Euro spec Sentra ) with some fuel efficiency issue and I was playing around looking at the ignition waveforms.

This car uses a distributor with a built in coil and optical CMP sensor. It has about 350k kilometers on it and probably the cap and rotor are the original ones. Now I know many would say right off just replace the cap and rotor, but that's not possible. This particular dizzy was only used on a few models between 97-99 and not even the Nissan dealership can order those parts, they just don't exist. My only option would be to replace the entire dizzy with an aftermarket one imported from another country.

So at the moment, I'm just really trying to understand what I'm seeing on the screen. I uploaded a short idle capture here:



If you watch it at 25% speed you can see each individual spark, and it looks a bit crazy to me. Here are a few a pulled out as examples:









I always understood that the primary and secondary should basically be mirror images of each other, but that doesn't seem to be the case here.

Based on these secondaries, I would expect it to be misfiring like crazy, but it seems to be running OK, other than some fuel efficiency issues.
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01 Feb 2018 09:15 #17443 by SailorBob
Here's an update to the primary vs. secondary issues I was seeing on the Almera above.

I bought a second HT25 because I thought maybe mine was defective and got the same results, on multiple different vehicles. It also seems that it readily accepts interference from any source; if it's placed too close to the coil pack or alternator it can cause the software to lock up or loose communication with scope, just generally screw up, as can be seen twice during this video. These measure where taken on a 98 Mazda 626 GF.



Here are some captures from the above video. The first two are from throttle snaps.







I'm assuming this is the HT25 causing the problem, and that it's just a crappy quality secondary pickup.
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