Looking for some insight before throwing more parts at the problem. 2007 Mitsubishi Endeavor. 190k miles. Misfire on Cylinder 4. Swapped coil with cylinder 2 and confirmed misfire moved to cylinder 2. Bought a used coil from junkyard (60k miles). Put it in cylinder 4. Car runs great.
Replaced all 6 spark plugs with new NGK iridium. Confirmed all plugs were correct gap out of the box.
After about 20 miles of driving, cylinder 4 starts misfiring again. Swap coil. Code moves. Looks like I killed another ignition coil.
Did I just get a bad coil or is there something going on that could be damaging the number 4 coil specifically? Computer problem?