Orifice Spark Advance Control: Description
The Orifice Spark Advance Control (OSAC) valve is used on some engines to assist in control of NOx emissions. This system controls vacuum to the vacuum advance actuator of the distributor. A tiny orifice in the OSAC valve delays ported vacuum to the distributor for about 10-27 seconds (depending on application), when going from idle to part throttle. When changing from part throttle to idle, vacuum change is instantaneous.
NOTE:
For vacuum hose routings on all engines, see CHRYSLER CORP. VACUUM DIAGRAMS at end of this section.