Air/Fuel Mixture: Testing and Inspection
IDLE MIXTURE CHECKRequired Special Tool:
^ MB991958: Scan Tool (MUT-III Sub Assembly)
^ MB991824: W.C.
^ MB991827: USB Cable
^ MB991911: Main Harness B
1. Before inspection, set vehicles in the following condition:
^ Engine coolant temperature: 80 - 95°C (176 - 203°F)
^ Lights and all accessories: OFF
^ Transaxle: Neutral (P range on vehicles with A/T)
CAUTION: To prevent damage to scan tool MB9911958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB9911958.
2. Connect scan tool MB991958 to the data link connector.
3. Check that the basic ignition timing is within the standard value.
Standard value: 50 BTDC ± 3°
4. Start the engine and increase the engine speed to 2,500 r/min for 2 minutes.
5. Set the CO, HC tester.
6. Check the CO contents and the HC contents at idle.
Standard value:
CO contents: 0.5 % or less
HC contents: 100 ppm or less
7. If the CO and HC contents do not remain inside the standard value, check the following items:
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.
^ Diagnostic 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 pressures
^ Injector
^ Ignition coil, spark plug cable, spark plug
^ EGR system and EGR valve leak
^ Evaporative emission system
^ Compression pressure