Ignition Timing: Adjustments

Basic ignition Timing Adjustment 3.9L Engine

1. Locate and ground out the carburetor switch idle stop contact with a suitable jumper wire.
2. Disconnect and plug the vacuum lines at vacuum transducer on the SCC and the air switching valve on the emissions air pump.
3. Set the gearshift selector in park or neutral and apply the parking brake.

4. Using a magnetic timing unit, insert the pickup probe into the open receptacle at the left of the engine between the power steering and the water pumps. If a magnetic timing unit is not available, use a conventional power timing light connected to the number one cylinder spark plug wire.
5. Bring the engine to a normal running temperature. This can be done by allowing the engine to idle for 5 to 10 minutes when the ambient temperature is around 21°C (70°F).
6. Adjust the engine idle rpm to the specifications on the VECI label in the engine compartment.
7. Check the basic timing when using a power timing light). If the basic timing is correct, remove the jumper wire, reconnect the vacuum lines and disconnect all test equipment. If the basic timing is NOT correct, proceed to step 8.






8. Loosen the distributor hold-down bolt allowing the distributor to be turned with some resistance and adjust the basic ignition timing to the specifications on the VECI label. After adjusting the basic ignition timing, recheck the idle rpm and secure the distributor. Recheck the timing once again to verify that the timing is correct.

9. Remove the jumper wire, reconnect the vacuum lines and check the idle rpm (adjust if necessary), disconnect all test equipment.