Ignition Timing

Inspection

NOTE: In addition to the scan tool (#MB991958), the following special tools are needed for this procedure:

• VCI (#MB991824)
• USB Cable (#MB991827)
• Main Harness B (#MB991911)

1. Before inspecting the ignition timing, do the following:
   • Step 1: Set the engine coolant temperature to 176 - 203°F (80 - 95°C).
   • Step 2: Turn OFF the lights and all accessories.
   • Step 3: Set the transaxle to Neutral (on vehicles with A/T, set it to the P range).

   CAUTION
   To prevent damage to scan tool (special tool #MB991958), always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool.

2. Connect scan tool (special 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. Use the scan tool (special tool #MB991958) actuator test "item number 17".
7. Make sure the basic ignition timing is within the standard value of 5° BTDC ± 3°.
8. If the basic ignition timing is not within the standard value, inspect the following:
   • Step 1: Diagnostic output
   • Step 2: Timing Belt Cover and crankshaft position sensor installation conditions
   • Step 3: 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. Make sure the actual ignition timing is at the standard value of approximately 15° BTDC.

NOTE: The ignition timing generally fluctuates about ± 7° before Top Dead Center, under normal operating conditions. In higher altitudes, the timing is automatically advanced by approximately 5° to 10° Before Top Dead Center.