Shared wasted spark coil caputures

Customer complaint misfire after 1/2 mile from a cold start, MIL illuminated and then cleared after 100 yards or so. P0302 stored.
4 cylinder, the ignition system is wasted spark with two plug top coils mounted on spark plugs 1 and 3 with short plug wires to the compainion cylinders.



First capture No2 Plug secondary at idle



On removing No2 Plug there was nothing obvious apart from general light deposit and the gap was excessively narrow 0.025" spec is 0.044"

The next capture is at normal idle after replacing No 2 plug



The next capture was taken at normal idle after replacing the companion No 3 spark plug and No 2 plug wire, vertical v/div scaling was changed to be 100% sure this was firing event not a wasted spark.



The final wave was taken at a snap throttle after repair, misfire hasn't returned after 3 weeks use.