Air/Fuel Mixture: Testing and Inspection
IDLE MIXTURE CHECKRequired Special Tool:
MB991958: Scan Tool (M.U.T.-III Sub Assembly)
^ MB991824: V.C.I.
^ MB991827: M.U.T.-III USB Cable
^ MB991910: M.U.T.-III Main Harness A
1. Before inspection, set the vehicle 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)
NOTE: On vehicles for Canada, the headlight, taillight, etc. remain lit even when the lighting switch is in "OFF" position but this is no problem for checks.
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. Turn the ignition switch to the "LOCK" (OFF) position and connect the scan tool MB991958 to the data link connector.
3. Start the engine and increase the engine speed to 2,500 r/min for 2 minutes.
4. Check that the actual ignition timing is within the standard value.
Standard value: Approximately 10° BTDC
NOTE: ignition timing fluctuates.: ± 7°, even under normal operating condition.
NOTE: It is automatically further advanced by about 5° from 10° Before Top Dead Center at higher altitudes.
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
^ EGR system
^ Evaporative emission system
^ Compression pressure
8. Remove the timing light and CD, HC tester.
9. Turn the ignition switch to the "LOCK" (OFF) position and disconnect the scan tool MB991958 from the data link connector.