PicoScope 7 Automotive
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Ford ignition primary waveform
Ford ignition primary waveform
Hello,
I am just getting started using a scope, and I am trying to interpret the ignition primary voltage waveform from a 1999 Ford Escort. The waveforms are not consistent. Some of them have some large spikes and dips after the spark starts and I don't know what to make of those, but they don't look like the good reference waveforms. Others look okay to me, but again, I am just getting started with using a scope. I'll attach a picoscope file to the post. The car is having some misfire issues, but they don't seem to affect any particular cylinder. I'm trying to figure out what I should check next and I am hoping that the scope will give me some direction. I already replaced spark plugs and wires because I found some carbon tracking on two of the plugs from companion cylinders 2 and 3. Also, the plugs did not meet the specs in the Ford service manual when I checked them with an Ohm meter.
This car uses two coils and a waste-spark ignition system. 12v power is supplied to the coils via a wire, and the coils are ground side switched via two wires that run to the PCM.
Thank you!
I am just getting started using a scope, and I am trying to interpret the ignition primary voltage waveform from a 1999 Ford Escort. The waveforms are not consistent. Some of them have some large spikes and dips after the spark starts and I don't know what to make of those, but they don't look like the good reference waveforms. Others look okay to me, but again, I am just getting started with using a scope. I'll attach a picoscope file to the post. The car is having some misfire issues, but they don't seem to affect any particular cylinder. I'm trying to figure out what I should check next and I am hoping that the scope will give me some direction. I already replaced spark plugs and wires because I found some carbon tracking on two of the plugs from companion cylinders 2 and 3. Also, the plugs did not meet the specs in the Ford service manual when I checked them with an Ohm meter.
This car uses two coils and a waste-spark ignition system. 12v power is supplied to the coils via a wire, and the coils are ground side switched via two wires that run to the PCM.
Thank you!
- Attachments
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- escort-new-plugs-wires-20190629-0001.psdata
- (1.55 MiB) Downloaded 400 times
Re: Ford ignition primary waveform
Hi Hepcat
Those waveform don't look too bad, particularly if you add a bit of filtering. Quite often it take a snap of the throttle for ignition to breakdown.
Scanner Danner does some great videos on analysing Primary and Secondary Ignition on you tube.
https://www.scannerdanner.com/78-secondary-ignition-waveforms-
I can see some turbulence within the firing line but I am not sure i would worry about that too much for now.
You may find that this maybe not be Ignition related, perhaps it is running lean so it may be an idea to look at fuel trims, 02 Sensors, Crank Sensor with a Math Channel for Cylinder Contribution / Smooth Running, MAP or MAF ....
At least narrow the misfires down to Fuel, Ignition or Whatever else then pops up.
The joy of the Pico is the Zoom function so get more time hence events on the screen (at least 2 revolutions of the engine) then zoom in and analyse. So much better to have 4 or even 8 events across the screen to compare.
Those waveform don't look too bad, particularly if you add a bit of filtering. Quite often it take a snap of the throttle for ignition to breakdown.
Scanner Danner does some great videos on analysing Primary and Secondary Ignition on you tube.
https://www.scannerdanner.com/78-secondary-ignition-waveforms-
I can see some turbulence within the firing line but I am not sure i would worry about that too much for now.
If I am reading this right then it appears you have misfires, or partial misfires across all the cylinders. A rough idle maybe ?? Please elaborate.but they don't seem to affect any particular cylinder.
You may find that this maybe not be Ignition related, perhaps it is running lean so it may be an idea to look at fuel trims, 02 Sensors, Crank Sensor with a Math Channel for Cylinder Contribution / Smooth Running, MAP or MAF ....
At least narrow the misfires down to Fuel, Ignition or Whatever else then pops up.
The joy of the Pico is the Zoom function so get more time hence events on the screen (at least 2 revolutions of the engine) then zoom in and analyse. So much better to have 4 or even 8 events across the screen to compare.
Re: Ford ignition primary waveform
I did a power balance test using my scan tool and I'm attaching the results. I looked at the voltage waveforms on the injectors and they are very consistent. I'll see if I saved those and if so, I'll post them later.
I also checked the crank sensor waveform and it looks very similar to what a good waveform is supposed to look like.
I also checked the crank sensor waveform and it looks very similar to what a good waveform is supposed to look like.
- Attachments
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Re: Ford ignition primary waveform
We can see that Cylinder #1 has no misfires & #3 has the most at 176. So rough running is proved.I did a power balance test using my scan tool and I'm attaching the results.
Does it get better if you increase RPM ?
To be fair we sort of already know that because it starts and runs. Add to that #1 has no misfires. that takes this away from being a Crank sensor issue.I also checked the crank sensor waveform and it looks very similar to what a good waveform is supposed to look like
However we can add a math channel to the Crank sensor signal to see much more clearly how the engine is rotating - see the misfires happen in real life and how regular they are. Add other channels, for example Upstream 02, MAF/MAP, Injector Duration Primary Ignition ... ..... ...... and you will get lucky and find WHY these misfires are occurring.
A relative compression test, then running compression's might be a great place too start. Also do the Primary's again with snap throttle.
Re: Ford ignition primary waveform
How about putting some time onto the screen so that we can also see the waste spark too. 500m/sec would be
a good start, also adjust your sample rate.
a good start, also adjust your sample rate.
Re: Ford ignition primary waveform
Also secondary ignition if possible.