Spark Timing Control System: Description
The spark timing control system aids in reduction of exhaust emissions by delaying vacuum to distributor vacuum advance unit during acceleration. On 2.0L engines, system consists of a vacuum delay valve, which is located in vacuum line between distributor and carburetor (Federal) or thermo valve (California).
On 2.3L engines (Calif. only), system consists of a spark delay valve (man. trans. only), and a distributor solenoid valve installed in vacuum line between intake manifold and distributor. The distributor solenoid valve is controlled by a timer and, on vehicles with automatic transmissions, a thermo switch.