The engine wiring harness insulation near the ignition coil connectors prematurely deteriorated due to prolonged exposure to engine heat in the turbocharger/exhaust area. Multiple wiring connectors exhibited brittle, cracked insulation with exposed conductors. The degraded wiring began shorting within the ignition system, causing engine misfires, ignition circuit faults, and eventual loss of engine operation. While being operated by a rental customer the vehicle developed severe misfires followed by electrical shorting, smoke, localized flames in the engine harness area, and eventual engine shutdown. The flames self-extinguished after the electrical shorting stopped, but portions of the harness insulation showed thermal damage and overheating. The customer became stranded due to the vehicle becoming inoperable. Diagnostic faults included ignition coil circuit open faults and ignition primary circuit faults. The vehicle ultimately became inoperable due to the electrical failure. Inspection revealed multiple adjacent ignition harness connectors showing progressive heat-related insulation degradation in the same high-temperature area, indicating a broader harness material failure rather than isolated damage. This failure occurred on a 5-year-old vehicle. Engine wiring harness insulation should not prematurely degrade and short under normal operating conditions.