Engine Starts But Stops

Ensure electrical harness, connectors and wires are not broken or loose. Ensure battery voltage is at least 11.5 volts. Check system relay and fuel pump relay. On turbo models, check pressure switch. Check all ECU input signals.
Check coolant temperature sensor operation.
Check induction system. Check for air leaks downstream of throttle valve, using pressure tester. Visually inspect between mass airflow meter and throttle housing.
Check auxiliary air valve for leaks and proper operation.
CO too high or too low.
Check throttle position sensor for proper adjustment or malfunction.