> Well, yes, but currently it's on my bench, not on the vehicle. However,
> when I generate sparks (I got the coil and all on my bench, it's a CDI
> that I'm designing) then every n (random) seconds the MPU crashes. If
> instead of the spark I use a resistor (~same discharge current of the
> coil) then no problems arise, hence I thought it was an EMI problem.


So now you're down to impedance, decoupling and layout issues.
Have you checked your design to see that all circuits are built with
the lowest practical impedance?
Decoupling can be critical. 0.1uF is not always the best value.

Build a noise probe, using a relay wired as a buzzer and a series LC
across the contacts, with the L being a small (pencil-eraser sized)
coil.  Use this to probe for weak points and evaluate.  Change design
as needed.
--=20
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