joscorstjens wrote:My investigation started because my rpm-gauge was fluctuating heavily . It is connected to the wasted-spark ignition coil through 2 diodes and a zener diode on a pinto 2.0 injection engine.
I just measured cyl 1 secondary voltage (through capacitive pickup picoscopeprobe) which is going all over the place (from 1.5 up to > 20 kVolt) while the current through the primary coil is quite constant (from 4 to 7 amp) depending on the amount of dwell (2.3 to 4.4) I put in.
The attachments contain a view of the combined current and voltage reading on picoscope 4223 (third attach) the other two show a zoom of a lower voltage ignition spike.
The .psdata file seems too big to attach.
This pattern is similar on all 4 cylinders.
Injection and timing is ok and the car runs fairly well but a bit 'irregular'.
So what could be the cause of this?
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