Top secret electronic ignition ??? ....
MC3334P clone ?

- ADC inputs have a maximum input feed impedance to respond as fast as required ... see Pic datasheet for details.

so, I presume @ first sight your current detection is wayyyy too slow, and your coil enters saturation ...

add to that your IPB protection is wayyy too weak and slow !!! be prepared for in-use failures, after some running time.

Now, automotive circuits need lots of filtering to avoid pic supply surges ...

Alain