As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ENGINE MISFIRING AT ALL POWER SETTINGS. DIAGNOSED FAULT TO BE THE IGNITION HARNESS LEADS. UTILIZING AN EASTERN TECHNOLOGY IGNITION HARNESS TESTER. IT WAS DETERMINED ALL THE BOTTOM LEADS WERE EITHER INTERMITTENT OR NONFUNCTIONAL FOR BOTH MAGNETOS. INSTALLING A NEW HARNESS COMPLETELY ELIMINATED THE MISFIRE CONDITION.