Ignition Timing Check

Required Special Tool: 

MB991502: Scan Tool (MUT-II)

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)
   CAUTION: To prevent damage to scan tool MB991502, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502.
2. Connect scan tool MB991502 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 MB991502 actuator test "item number 17."
7. Check that basic ignition timing is within the standard value.

   Standard value: 5° BTDC +/- 3° 

   Fig 1: Connecting Scan Tool MB991502 To Data Link Connector

   Courtesy of DAIMLERCHRYSLER CORPORATION
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 MB991502 (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 15° 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.