Idle/Throttle Speed Control Unit: Description and Operation

The digital idle stabilizer (DIS) is used on fuel injected (CIS) vehicles built for California and carbureted vehicles only. The DIS keeps the idle speed within a specified range regardless of the loads that are placed on the engine (cooling fan, A/C, etc.). Idle stabilization works by advancing and retarding the ignition timing. Since the idle stabilizer only operates under 950 RPM, the timing is not affected when the vehicle is operating above idle.