Dieseling, Run on

DEFINITION:
Engine continues to run after key is turned "OFF", but runs very roughly. If engine runs smoothly, check ignition switch and adjustment.

CHECK
- Fuel injector leaking
- Obvious overheating problems, 85°C-100°C (185°F-215°F) is normal.
Low coolant.
Loose water pump belt.
Restricted air flow to radiator, or restricted water flow thru radiator.
Faulty or incorrect thermostat.
Correct coolant solution - should be a 50/50 mix of anti-freeze/coolant and water.