Ignition Timing: Adjustments

Timing Marks:

ALDL Connector:

PROCEDURE
An averaging method is used to check the ignition timing for this engine. The averaging method is a process in which the timing of each cylinder can be brought into closer agreement with the base timing specification. Refer to the underhood "Emission Control Label" and follow the instructions.

SET TIMING UNDER THE FOLLOWING CONDITIONS
1. Verify that NO "SERVICE ENGINE SOON" light exists.
2. The vehicle should be running at normal operating temperature.
3. All engine loads should be "OFF."
4. The transmission should be in Park or Neutral.
5. The engine should be running at idle speed.

ADJUSTMENT PROCEDURE
1. Ground the ALDL connector located under the dash. The "SERVICE ENGINE SOON" light will flash.
2. Connect a timing light inductive pick-up to the # 1 spark plug wire.
3. Record the position of the timing mark.
4. Connect the timing light to the # 4 spark plug wire and record the timing mark.
5. Add the total of the two readings, and divide by 2. This is the average timing.
6. If an adjustment is necessary, subtract the average timing from the specification. This is the amount the timing needed to be changed. Reconnect the timing light to the # 1 wire and adjust timing.
a. Loosen the hold down bolt, and rotate the distributor to adjust timing.
b. Tighten the hold down and recheck the timing.

7. Remove the ground from the ALDL connector and verify NO "SERVICE ENGINE SOON" light exists. Clear the ECM memory by disconnecting the positive battery pigtail for ten seconds with the ignition key in the "OFF" position.