Air/Fuel Mixture: Testing and Inspection

Idle Mixture Check
1. Before inspection, set the vehicle in the following condition.
- Engine coolant temperature: 80 - 95°C (176 - 203°F)
- Lights, electric cooling fan and accessories: OFF
- Transaxle: neutral (P for A/T)
2. Make sure that the basic ignition timing is of a standard value.
Standard value: 5° BTDC ± 3°
3. After turning the ignition switch OFF, set a tachometer or connect the scan tool to the data link connector.

NOTE: For tachometer setting procedure, refer to Ignition Timing.

4. Start the engine and run at 2,500 r/min for approx. 2 minutes.
5. Set the CO tester and HC tester.
6. Check the CO contents and HC contents with the engine at idle.
Standard value:
CO contents: 0.5 % or less
HC contents: 100 ppm or less
7. If the standard value is exceeded, check the following items.
- Diagnostic output
- Closed loop control (if closed loop control is performed normally, heated oxygen sensor output signals change within a 0 - 400 mV range and a 600 - 1,000 mV range.)
- Fuel pressure Injectors
- Ignition coil, spark plug cables and spark plugs
- Leaks in EGR system and EGR valve
- Evaporative emission control system
- Compression pressure

NOTE: If CO and HC concentrations exceed the respective standard values despite the fact that the results of the inspection made on all items are normal, replace the three-way catalyst.