Intermittent Malfunction Indicator Light (Mil)

Check for electrical system interference from faulty relay, ECM-driven solenoid or switch. Faulty components can cause sharp electrical surge when operated.
Check for incorrect installation of electrical options (2-way radios, cellular phones, etc.). Ensure EST ignition wiring is routed away from spark plug wiring. Ensure distributor is properly grounded.
Check for ignition secondary circuit shorted to ground. Check for shorted MIL circuit. Check for poor ECM grounds.