Jetta L4-1781cc 1.8L SOHC (RV, PF) (1989)
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When the control unit recognizes that the idle speed is not within specified ranges, approx. 800-900 RPM, the necessary correction value is calculated
and current to the idle stabilizer valve is changed. This change in current adjusts the valve opening to allow more or less air to bypass the throttle valve
as necessary to maintain the correct idle speed.
The current from the control unit ranges from 380 mA to 1000 mA.
If a fault occurs in the coolant temperature sensor circuits, or when the sensor is disconnected for basic engine adjustments, the control unit will use a
substitute value of approx. 420 mA to operate the idle stabilizer valve.
Vehicles Produced From Jan. 1989
Digifant II Engine Management System
The Digifant II control unit, which is located at the left rear of the engine compartment, is responsible for management of the fuel injection, ignition, and
idle speed systems. It receives and evaluates information provided by various sensors concerning engine operating conditions. Input signals to the
Digifant II control unit include:
^
A/C compressor "ON"
^
Air flow sensor
^
Coolant temperature sensor
^
Hall sender
^
Intake air temperature
^
Knock sensor
^
Oxygen sensor
^
Throttle valve switches
From the information received, the Digifant II control unit calculates appropriate values for the output components, which maintain optimum engine
performance and emission characteristics. Output signals from the Digifant II control unit include:
^
Diagnostic codes
^
Fuel Injectors
^
Fuel pump relay
^
Idle stabilizer valve
^
Hall control unit
FUEL INJECTION CONTROL
Fuel injection quantity is controlled by the Digifant II control unit. The basic fuel injector opening time is calculated by the E.C.U. using information
from the airflow meter signal and the engine speed signal. The injector opening time (pulse width), is then modified by additional input signals to the
E.C.U. for the functions of cold start enrichment, warm-up enrichment, full throttle enrichment, deceleration fuel shut-off, and over-rev fuel shut-off;
depending on engine operating conditions.
FAIL-SAFE OPERATION
