Idle Mixture Check

Required Special Tool: 

MB991958: Scan Tool (MUT-III Sub Assembly)

• MB991824: V.I.C.
• MB991827: USB Cable
• MB991911: Main Harness B

1. Before inspection, set vehicle to the following conditions:
   • Engine coolant temperature: 80-95°C (176-203°F)
   • Lights and all accessories: OFF
   • Transaxle: Neutral
   CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958. 
2. Connect scan tool MB991958 to the data link connector.
3. Confirm basic ignition timing is within the standard value. (Refer to IGNITION TIMING CHECK  .)
   1. Standard value: 5° BTDC +/- 3° 
4. Increase engine speed to 2,500 r/min for 2 minutes.
5. Set the CO/HC tester.
6. Check the CO and HC contents at idle.
   1. Standard value: 
      1. CO contents: 0.5 % or less 
      2. HC contents: 100 ppm or less 
7. If the CO and HC contents do not remain inside the standard value, check the following items:
   • If the MFI system diagnostic trouble code is output
   • Closed-loop control (When the closed-loop control is carried out normally, the output signal of the heated oxygen sensor changes between 0-400 mV and 600-1,000 mV at idle.)
   • Fuel pressure
   • Injector(s)
   • Ignition coil, spark plug cable, spark plug
   • EGR system and EGR valve leak
   • Evaporative emission system
   • Compression pressure
   NOTE: Replace the catalytic converter when the CO and HC contents do not remain inside the standard value, even though the result of the inspection is normal for all items.
   Fig 1: Connecting Scan Tool MB991958 To Data Link Connector

   Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.