The Integrated Vehicle Speed Control (IVSC) system consists of operator controls, servo (throttle actuator), brake light switch, speed sensor (not required for vehicles equipped with an electronic cluster), horn relay, vacuum dump valve, vacuum reservoir (called an aspirator on some models), check valve(s), wiring and hoses for vacuum. The vacuum reservoir or aspirator provides an additional vacuum signal when the engine is under heavy load to improve speed control performance. In the IVSC system, speed control amplifier assembly function has been integrated into the EEC-IV Electronic Control Assembly (ECA). The servo assembly is mounted in the engine compartment and is connected to the throttle linkage with an actuator cable. The servo is connected to the vacuum reservoir (aspirator) and to manifold vacuum through the check valve. The speed control sensor is located on the transmission or transaxle.
For the system to be activated, the engine must be running and the vehicle must be greater than approximately 25-35 mph (40-56 km/h), depending upon vehicle application. Under these conditions, the system is activated and is ready to accept a set speed signal by pressing the ON switch in the steering wheel. Then, the operator must depress and release the SET ACCEL switch. This will result in the current speed being maintained until a new speed is set by the operator, the brake pedal is depressed, the clutch pedal is depressed or the OFF switch is depressed.
To decrease the set speed, the vehicle speed may by reduced by applying the brake or clutch pedal and then resetting the speed using the foregoing method or by depressing the COAST switch. When the vehicle has slowed to the desired speed, the COAST switch is released and the new speed is set automatically. If the vehicle speed is reduced below approximately 25-35 mph (40-60 km/h), depending upon vehicle application, the operator must manually increase the speed and reset the system.
To increase the set speed, the vehicle set speed may be manually increased at any time by depressing the accelerator until the higher speed is reached and stabilized, then depressing and releasing the SET ACCEL button. Speed may also be increased by depressing the SET ACCEL switch button, at speeds over approximately 25-35 mph (40-56 km/h), depending upon vehicle application, and holding it in that position. The vehicle will then automatically increase speed. When the desired rate of speed is attained and the button is released, that new set speed will be maintained.
The speed control system may be deactivated by depressing the brake or clutch pedal. To resume the set speed prior to deactivation, the RESUME switch is depressed and prior set speed may be re-established. The RESUME switch is hinged on the side closest to the SET ACCEL switch. Therefore, it should be depressed on the side farthest from the SET ACCEL switch. The resume feature will not function if the system is deactivated with the OFF switch, or if the vehicle speed has been reduced to below approximately 25-35 mph (40-56 km/h) depending upon vehicle application. In addition, when the ignition switch is turned OFF , the speed control memory is erased and the resume feature will not function.