Ignition Timing: Testing and Inspection
IGNITION TIMING CHECKRequired Special Tool:
MB991958: Scan Tool (MUT-III Sub Assembly)
^ MB991824: V.C.I.
^ MB991827: MUT-III USB Cable
^ MB991911: MUT-III Main Harness B
1. Before checks, set the vehicle in the condition:
^ Engine coolant temperature: 80 - 95 °C (176 - 203 °F)
^ Lights and all accessories: OFF
^ Transaxle: P range
NOTE: 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. 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 750 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 ± 3 °BTDC
8. If the basic ignition timing is not within the standard value, check the 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 °BTDC, even under normal operating condition.
NOTE: It is automatically further by about 5 - 10 °BTDC at higher altitudes.