I am using this way to sense the capacitive pickup and calculate RPM of an engine
The problem is when I am testing it openly it works fine and the RPM is calculate correctly
But when I am enclosing the arduino into a cabinet and after that any wires passing by the spark plug hangs arduino...
My main problem is that there are other wires from the analog and digital pins from the arduino which are passing through one sleeve . Now when this sleeve gets closer to the ignition coil the arduino hangs...
No guarantees of it fixing the problem, but it will suppress induced spikes traveling down the line.
If it doesn't fix it, it is an improvement and a step closer to solving it.
This sort of thing doesn't have a sure fire fix.