Failed Emissions Test

Test lambda control system. Replace if faulty.
Check air/fuel mixture. Adjust if necessary.
Ensure air intake system is not restricted.
Ensure engine is at normal operating temperature.
Ensure fuel system pressure is correct.
Check cold start valve for leaking (engine warm).
Check thermo time switch operation.
Verify base timing is correct.
Check for correct PCV valve operation.
Check crankcase for gasoline contamination.
Check idle stabilizer operation.
Check EGR system for correct operation (if equipped).
Check vapor recovery system operation.
Check operation of coolant temperature sensor.
Check fuel tank filler tube for tampering of restrictor. If tampering has occurred, check catalytic converter for lead contamination and exhaust system restriction.
Check for use of poor quality fuel containing insufficient cleaning additives. Prolonged use of poor quality fuel can cause injector clogging and carbon build-up on intake system.