Engine Control Module: Description and Operation

CIS-E System:

The CIS-E control unit, which is located under the dashboard and near the glove box, receives and evaluates information provided by various sensors concerning engine operating conditions. From the information received, the control unit calculates the appropriate output value for the differential pressure regulator, which is needed to maintain optimum engine performance and emission characteristics. Input signals include:

^ Coolant temperature sensor
^ Air flow sensor plate potentiometer
^ Oxygen sensor

Differential Pressure Regulator:

The differential pressure regulator controls pressure in the lower chambers of the CIS-E fuel distributor, therefore, regulating the pressure differential across the metering valves and the volume of fuel that is delivered to the injectors. It is controlled by current changes from the CIS-E control unit in response to different engine conditions.

After-Start And Warm-Up Enrichment Graph:

AFTER-START AND WARM-UP ENRICHMENT

To assure smooth engine operation during the after-start period the CIS-E control unit will enrichen the fuel mixture by increasing the current to the differential pressure regulator. The amount of enrichment is dependent on engine coolant temperature, and lasts for a maximum of 40 seconds.
The control unit continues fuel enrichment during the warm-up period based on coolant temperature. Warm-up enrichment continues, however, at a lower level than after-start enrichment and discontinues when the engine reaches normal operating temperature.

Acceleration Enrichment Graph:

COLD ACCELERATION ENRICHMENT

The CIS-E control unit increases current to the differential pressure regulator briefly when the engine is below normal operating temperature and the throttle valve is opened suddenly. This ensures good throttle response and the elimination of the familiar "flat spot" upon cold acceleration. The enrichment amount depends upon engine coolant temperature, position and movement speed of the air flow sensor plate (via the air flow sensor plate potentiometer), and engine RPM. Because of the resistance curve of the potentiometer, more enrichment will occur at low engine speeds and less at high engine speeds.