Ignition Timing Control System

On 1977 manual transmission equipped models, the ignition timing control system uses a transmission sensor controls the amount of spark retard during normal operation in 1st, 2nd and 3rd gears when thermo sensor in system is in the on position (warm engine) to minimize the emission of oxides of nitrogen (NOx).

On 1977 automatic transmission equipped models, the ignition timing control system controls the amount of spark retard by sensing vacuum in intake manifold and engine coolant temperature to minimize the emission of oxides of nitrogen (NOx).

The 1978-79 ignition timing control system controls the amount of spark retard by sensing intake manifold vacuum and coolant temperature. Spark retard is necessary to minimize oxides of nitrogen (NOx) emissions. The system eliminates spark retard when engine is cold, allows full retard during hot idling, and reduces retard during hot cruising. The system consists of a distributor vacuum diaphragm, an ignition solenoid valve, a delay valve and a thermo sensor.