Ignition Timing: Adjustments

Timing Mark:

Timing specifications for each engine are listed on the underhood Vehicle Emissions Control Information label in the engine compartment. Refer to 'SET IGNITION TIMING', for specific procedures to use when setting base engine timing.

The 4.9L engine incorporates a magnetic timing probe hole for use with special electronic timing equipment. The accompanying image shows a typical magnetic probe hole. Consult manufacturer's instructions for use of this equipment.

Malfunction codes may be set during ignition timing. Enter diagnostics and clear trouble codes if this occurs.

SET IGNITION TIMING

NOTE: Vehicle Emissions Control Information label in engine compartment also has procedures for setting ignition timing.

1. Place transmission in park.

2. With ignition OFF connect the pick-up lead of timing light to the number one spark plug. Use a jumper lead between the wire and plug or an inductive type pickup. DO NOT pierce the wire or attempt to insert a probe light power leads according to manufacturer's instructions.

NOTICE: Do not time engine on seven cylinders as the unburned fuel could cause damage to the catalytic converter.

3. With engine at normal operating temperature and A/C OFF take off air cleaner housing upper.

4. Jumper pins A & B at the ALDL connector while not in diagnostic display. 'SET TIMING MODE' message will be displayed on the Climate Control Driver Information Center (CCDIC).

5. Start the engine and aim the timing light at the timing mark, Figure 6. The line on the pulley will line up at the timing mark. If a change is necessary, loosen the distributor hold - down clamp nut with special tool J 29791 at the base of the distributor. While observing the mark with the timing light, slightly rotate the distributor until the line indicates the correct timing. Tighten the hold - down nut and re-check the timing.

6. Set base timing at 10 degrees BTDC at any speed less than 800 rpm.

7. Turn OFF the engine and remove the timing light. Reconnect the number one spark plug wire, if removed.

8. Remove the jumper from ALDL connector and install air cleaner housing upper.

Important

^ Remove the jumper from the ALDL connector when the procedure is complete. If the jumper remains in ALDL connector, engine will run at base timing and cause a driveability problem.