California Models

CIS-E Motronic Engine Management System:

The CIS-E Motronic control unit, which is located at the left rear of the engine compartment under the drip tray, receives and evaluates information provided by various sensors concerning engine operating conditions. It is responsible for management of the fuel injection, ignition, idle speed, and fuel tank evaporative emission control systems. Input signals to the Motronic control unit include:

^ Air flow sensor plate potentiometer
^ Automatic transmission selector switch
^ A/C compressor input
^ Coolant temperature sensor
^ Hall sender
^ Ignition reference sender
^ Knock sensors
^ Oxygen sensor
^ Throttle valve switches

From the information received, the Motronic control unit calculates the appropriate values for the output components, necessary to maintain optimum engine performance and emission characteristics. Output signals from the Motronic control unit include:

^ Cold start valve
^ Diagnostic codes
^ Differential pressure regulator
^ Fuel pump relay
^ Evaporative emission solenoids
^ Idle stabilizer valve
^ Ignition power output stage

ADAPTIVE FUEL MIXTURE CONTROL

In order to maintain proper performance and driveability over a wider range of conditions, and to reduce the need for minor periodical adjustments, the CIS-E Motronic control unit can adapt to minor intake leaks, engine wear, and sustained high altitude operation. It does this by learning the control values that are most often required to maintain correct engine operation under normal conditions. If the "learned" conditions of operation change (i.e. changing from driving at sea level 35 ft., to mountain driving at 3000 ft.) the control unit will adapt the air/fuel mixture to prevent the rich or lean condition that would result otherwise.

FAULT MEMORY

In the event of a CIS-E Motronic system malfunction, fault information will be stored in the internal memory of the Motronic control unit. Faults related to emissions and safety are stored in permanent memory and must be erased after repairs. Additional faults that can be recognized by the control unit are stored in a temporary fault memory and will be erased at the next engine start-up.
In addition to being stored in memory, an emissions-related failure will cause the "Check" light to illuminate on the instrument cluster.
Two methods may be used to retrieve fault codes. The VW special tool VAG 1551 tester, if availible, or a jumper wire and LED test light connected to the black, blue, and white connectors under the shift boot.

CIS-E Motronic Ignition Layout:

IGNITION TIMING POINT

The ignition timing point is determined by the CIS-E Motronic control unit. Information on engine load, speed and coolant temperature are processed by the control unit and compared to programmed "Basic Ignition Maps" in the control unit's permanent memory. These three dimensional ignition performance maps are used to optimize the ignition to achieve the most favorable exhaust gas emissions, fuel consumption, and engine performance characteristics for any given load or speed condition.

Timing Advance Map:

When the throttle valve is in the closed position, the bottom line of the basic ignition map is selected as the idle/coast characteristic. For engine speeds below the nominal values, the ignition timing is advanced to obtain idle stabilization. For coasting, ignition timing is programmed to obtain minimum exhaust gas pollutants and optimum driveability performance. For the wide open throttle position, the top line of the basic ignition map is selected. For very high ambient temperatures, the ignition is retarded as a function of engine and intake air temperature.

IGNITION KNOCK CONTROL

The CIS-E Motronic control unit actively controls knock "ping" allowing calibration of the ignition timing for normal operating conditions, while eliminating the danger of knock or detonation due to influences by engine heat, load, fuel quality or engine deposits.

Knock Sensor Location:

Two sensors which are located on the engine block (one sensor between #1 and #2 cylinders and one sensor between #3 and #4 cylinders) are subjected to vibrations generated by knock (ping). The vibrations cause a small distortion on the surface of the piezoelectric crystal, generating a measureable voltage which is read by the CIS-E Motronic control unit. The control unit will retard the ignition point for individual cylinders as necessary to eliminate the knock depending upon the intensity.

COLD START ENRICHMENT

The Motronic control unit determines the need for and controls the operation of the cold start valve. Control of the cold start valve occurs according to a CIS-E control unit map based on coolant temperature that creates a pulsating injection (duty cycle) of the cold start valve. Normal duty cycles range from 50% - 100%.
The cold start valve receives power whenever the ignition switch is in the "ON" or "RUN" position. The Motronic control unit determines how long the valve will be open by switching the ground side (duty cycle) of the circuit. The cold start injector is also activated if the engine does not start after approx. 2 seconds, at temperatures above 239°F.

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 Motronic control unit will richen 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 approx. 30 to 60 seconds.
The control unit continues with 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 Motronic control unit increases current to the differential pressure regulator briefly when the engine is below normal operating temperature and the throttle is opened suddenly. This ensures good throttle response and the elimination of the familiar "flat spot" upon cold engine 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.

Deceleration Fuel Shut-Off:

DECELERATION FUEL SHUT-OFF

Fuel deceleration shut-off increases fuel economy and aids in reducing exhaust emissions.
During engine deceleration, the CIS-E control unit reverses the current to the differential pressure regulator to approx. -40 mA. This raises pressure below the differential pressure valves so as to effectively shut off fuel to the injectors.
In order to accomplish smooth operation, the point at which fuel shut-off begins and ends, is depends on coolant temperature. If the engine has attained normal operating temperatures, fuel shut-off will occur when the engine speed is above approx. 1600 RPM and the throttle valve idle switch is closed. Current flow to the differential pressure regulator will return to normal when the engine speed drops below approx. 1300 RPM, restarting injection.

Idle Stabilizer Valve:

IDLE STABILIZATION CONTROL

The idle speed is electronically controlled by the CIS-E Motronic control unit with relation to engine coolant temperature and load signals.
If the control unit recognizes that the idle speed is not within specified ranges, approx. 800-900, the duty cycle for the idle stabilizer valve will be modified. This adjusts the valve open to allow more or less air to bypass the throttle valve as necessary to maintain the correct idle speed.