Ignition Timing: Testing and Inspection

IGNITION TIMING CHECK

Required 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. Set up a timing light.
4. Start the engine and run it at idle.
5. Check that the idle speed is approximately 700 r/min.
6. Select scan tool MB991958 actuator test "item number 17."
7. Check that basic ignition timing is within the standard value.
Standard value: 5° BTDC ± 3°
8. If the basic ignition timing is not within the standard value, check the following items:
^ Diagnostic output
^ Timing belt cover and crankshaft position sensor installation conditions
^ Crankshaft sensing blade condition

CAUTION: If the actuator test is not canceled, the forced drive will continue for 27 minutes. Driving in this state could lead to engine failure.

9. Press the clear key on scan tool MB991958 (select forced drive stop mode), and cancel the actuator test.
10. Check that the actual ignition timing is at the standard value.
Standard value: Approximately 10° BTDC

NOTE: Ignition timing fluctuates about ± 7° Before Top Dead Center, even under normal operating condition.

NOTE: It is automatically further advanced by about 5° to 10° Before Top Dead Center at higher altitudes.