I would like to get guidance and help with basic ignition diagnostics. I have done my homework reading the instruction material, watched hours and hours of videos but I have an situation where I can not access the device on a regular basis.
So the normal routine is that the only time I have with the scope is when the assigned tech is away, and it is handed over to me like a hot stone. This was exactly the case, a complaint about engine missing when flooring the car from 2000 rpm. After studdering to 3000 rpm, it went on to redline with adequate power and "no misses". Also there was some backfire. I had only 30 minutes with the car and no real life experience with ignition so I did my best. The engine had no CEL's, and on idle it was misfiring steadily, but barely noticeable. The engine was X28NET in a Vauxhall Vectra.
I understand I did not follow the right steps, and did not do the right measurements, but I would like to get help with basic secondary ignition setup. I am not allowed to practice after work, so I would have to get it right the next time.
The only cylinders there was time to look at were the ones in front. First I used the paddle, then HT extensions. This was basically the owner stading next to me and saying he wanted to get those 3 diagnosed
Is is possible to deem the coils in blue and green trace as faulty as the oscillations are missing, or is it a fault in my measurement? The red trace was somewhat OK, but not perfect.
Using the HT extension method, green trace of the coils was shorting from the frame to the engine time to time.
I would value input on,
-setting the timebase, trigger, and examining the traces
-is it ever a good idea to use low-pass filtering on ignition?
-why could not I trigger to a single ignition signal on auto or repeat so it would stay in center of the screen after trying almost all the possible variations on the position of the trigger? The best I could manage was on the falling edge on a steady part of the signal.
-how to get the details more visible, as they are the key in successful ignition diagnostics?
Using the scope must be learned by actually using it, but given the current situation I have to make the best of what it is. Any guidance is well appreciated!
I notice the same things from these after reviewing the HT-extension traces. Blue and green are missing the oscillations found in red? But can the waveform be more precise and defined?
not much to see there. KV very high. Try the HT leads again. More time on the screen. 500ms/div -5MS and
no trigger-repeat. you will get 4 screens. Also do not use Auto or any filtering. Filter after you got your screens.
Also label the channels. capture at idle and one under load.
Hope that helps to start
I was able to do some captures with normal oil changes just to practice. 500m/s and I still fail to understand the waveform in diagnostic point of view. This was from an Audi A2. After watching numerous videos again, it is possible to get good quality capture with cheap equipment, and somehow I still fail to do it with Pico. This was taken with secondary pickup straight from the wire.
Hi, in your first download I'd say you need to look closely at the secondary ignition. In the second example I'd say you need to adjust your scope settings. I have included two captures from your scope traces expanded so that you can see the relevant parts.
Attachments
Ignition Capture.JPG (19.05 KiB) Viewed 7589 times
Blue trace, a lean condition as the nose is too high?
Red trace, I got nothing. I really tried but I can not say what is wrong in the waveform, or in my capture.
Blue trace had a normal waste spark system I believe, but the red capture in terms of the longer waveform was unlike any I have seen yet.
Thank you for your advice, I really tried to think what's going on. I wanted to know what is wrong with my settings so once I can get good captures, I can start looking and learning what is actually going on.