Fails Emission Test

Check for clogged air filter.
Check for engine not at normal operating temperature.
Check for fuel leakage from injectors.
Check for fuel pressure out of specification.
Check for faulty coolant (water) temperature sensor.
Check for faulty air temperature sensor (if equipped).
Check for faulty ECM.
Check for faulty EGR system (if equipped).
Check for improper ignition timing.
Check for lead contamination in catalytic converter.
Check for malfunctioning ignition system.
Check for misrouted vacuum hoses.
Check for poor compression.
Check for vacuum leaks.