Need Help interpreting this ignition waveform

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AnilS
Newbie
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Joined: Fri Aug 31, 2018 1:42 am

Need Help interpreting this ignition waveform

Post by AnilS » Wed Sep 05, 2018 8:58 pm

Hi, Im new to picoscope and vehicle diagnosis, in possession of my 4425 scope a week now and the first vehicle I decided to poke around in gave me some weird ignition waveforms. Vehicle is a 2012 subaru forrester with a misfire. Waveform taken with the COP Probe.
Capture.JPG
Ignition spikes can also be seen at the Map and Maf blue trace is MAP
Capture2.JPG
All four coils displays this type of waveforms. Can all four coils be bad ? or can this be a faulty ground or something??????
thanks for the assistance.

Dejan
OneWave
OneWave
Posts: 28
Joined: Sat Jun 07, 2014 10:00 pm

Re: Need Help interpreting this ignition waveform

Post by Dejan » Thu Sep 06, 2018 8:49 am

I think that ignition spikes/noise is normal on MAP and MAF sensor.

Noise/hash on ignition waveform is maybe due to current limiter in PCM (when it kicks in) but you should scope primary voltage and current to confirm that...

:)

liviu2004
TwoWaves
TwoWaves
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Joined: Sat Mar 19, 2016 8:23 am
Location: Netherlands

Re: Need Help interpreting this ignition waveform

Post by liviu2004 » Thu Sep 06, 2018 1:29 pm

Lean burning, misfire caused by lack of fuel. Sufficient energy left in the coil.
What is the burn time? Where is the time scale?

AnilS
Newbie
Posts: 3
Joined: Fri Aug 31, 2018 1:42 am

Re: Need Help interpreting this ignition waveform

Post by AnilS » Thu Sep 06, 2018 8:20 pm

Trying to upload the waveform but the file is too large. I measured some captured events and most burn times are about 425ms and 321ms.
Thanks for the assistance pointing out the lean misfire, my focus was on the noise during the dwell time. I only had about a half hour with the vehicle, but will make some time this weekend for some poking around.

liviu2004
TwoWaves
TwoWaves
Posts: 122
Joined: Sat Mar 19, 2016 8:23 am
Location: Netherlands

Re: Need Help interpreting this ignition waveform

Post by liviu2004 » Fri Sep 07, 2018 11:33 am

Maybe nanoseconds instead of miliseconds? Ideally burn time should be 1-1.2 ms.

Tucan
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Joined: Sun Apr 02, 2017 3:52 am

Re: Need Help interpreting this ignition waveform

Post by Tucan » Sun Oct 28, 2018 3:58 am

El ruido que se ve en la sección de dwell puede estar siendo causado por fallas en el circuito de disparo de las bobinas de encendido.
Tu puedes comprobar esto con una sonda de corriente enganchada al alambre negativo de las bobinas. Si ves que el oscilograma de corriente en rampa de la bobina tiene caídas intermitentes, entonces revisa las caídas de voltaje en los circuitos de tierra y potencia de la computadora, si estos están bien entonces, la computadora esta fallando.
Siento mucho no poder escribir en ingles pero solo puedo leerlo.


Google Translate
The noise seen in the dwell section may be caused by faults in the firing circuit of the ignition coils.
You can check this with a current probe attached to the negative wire of the coils. If you see that the ramp-current oscillation of the coil has intermittent drops, then check the voltage drops in the earth and power circuits of the computer, if these are OK then, the computer is failing.
I'm sorry I can not write in English but I can only read it.

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