Idle Mixture Check

Required Special Tools: 

• MB992744: Vehicle communication interface-Lite (V. C. I.-Lite)
• MB992745: V. C. I.-Lite main harness A
• MB992747: V. C. I.-Lite USB cable short
• MB992748: V. C. I.-Lite USB cable long
• MB991958: Scan Tool (M. U. T.-III Sub Assembly)
  • MB991824: Vehicles Communication Interface (V. C. I.)
  • MB991827: M. U. T.-III USB Cable
  • MB991910: M. U. T.-III Main Harness A (Vehicles with CAN communication system)

1. Before inspection, set the vehicle to the pre-inspection condition.
   CAUTION: To prevent damage to scan tool (M. U. T.-III), always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool (M. U. T.-III).
2. Turn the ignition switch to the "LOCK" (OFF) position and then connect scan tool (M. U. T.-III) to the data link connector. (Refer to DIAGNOSTIC FUNCTION ).
3. Set the timing light to the power supply line (terminal No. 3) of the ignition coil No. 1.
   NOTE: The power supply line is looped and also longer than the other ones.
4. Start the engine and let it run at idle.
5. Check that the actual ignition timing is at the standard value.

   Standard value: Approximately 5° BTDC 

   NOTE: The ignition timing fluctuates about ± 7°, even under normal operating condition.
   NOTE: It is automatically further advanced by about 5° from 10° Before Top Dead Center at higher altitudes.
   NOTE: Wait till approximately 1 minute passes after the engine started, and check the ignition timing when the engine stabilized.
6. Run the engine and increase the engine speed to 2,000 - 3,000 r/min for 2 minutes.
7. Set the CO, HC tester.
8. Check the CO contents and the HC contents at idle.

   Standard value: 

   CO contents: 0.5% or less 

   HC contents: 100 ppm or less 

9. If there is a deviation from the standard value, inspect the MFI system. (Refer to SYMPTOM CHART ).
10. Remove the CO, HC tester and timing light.
    Fig 1: Identifying Ignition Coil No.1 And Timing Pickup Loop

    
    CAUTION: To prevent damage to scan tool (M. U. T.-III), always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool (M. U. T.-III).
11. Turn the ignition switch to the "LOCK" (OFF) position and then disconnect the scan tool (M. U. T.-III).