Except SPFI

Ignition control system is designed to reduce emissions throughout all engine operating ranges by controlling ignition timing. System consists of a vacuum advance control unit, distributor, thermo vacuum valve on Multi-Point Fuel Injected (MPFI) models, sub-advance control solenoid valve on Federal 2WD and California carbureted models, restrictive orifice on MPFI models, check valve on turbo models and vacuum lines. The thermo vacuum valve also operates canister purge system.

A dual-diaphragm (main and sub-advancer) type vacuum controller is used on Federal 2WD and California carbureted models, and MPFI non-turbo models. A single diaphragm (advancer) type vacuum controller is used on Federal 4WD and MPFI turbo models.