E - THEORY/OPERATION
1993 ENGINE PERFORMANCE
Volkswagen Theory & Operation - Motronic
Corrado SLC
INTRODUCTION
This article covers basic description and operation of engine
performance-related systems and components. Read this article before
diagnosing vehicles or systems with which you are not completely
familiar.
COMPUTERIZED ENGINE CONTROLS
ELECTRONIC CONTROL UNIT
The Motronic engine management system uses a single
Electronic Control Module (ECM) for fuel injection, idle speed
control, ignition, and emission controls. The Electronic Control
Module (ECM) continually corrects air/fuel mixture based on signals
from various signals. The ECM is located underneath center of
windshield cowl, directly behind engine compartment firewall.
NOTE: Components are grouped into 2 categories. The first category
covers INPUT DEVICES, which control or produce voltage
signals monitored by the control unit. The second category
covers OUTPUT SIGNALS, which are components controlled by
the control unit.
INPUT DEVICES
Engine Coolant Temperature (ECT) Sensor
Sensor is located on thermostat housing. As engine coolant
temperature increases, the resistance of the sensor decreases. Engine
coolant temperature sensor signals are used for control of ignition
timing, injector pulse width, and idle speed stabilization. In
addition, knock sensors, idle speed control, oxygen sensor and fuel
tank venting are activated based on coolant temperature.
Engine Speed (RPM)/Reference Sensor
Engine speed (RPM) and crankshaft position are registered by
a single sensor located on side of engine block. The sensor reads a
toothed wheel mounted on the crankshaft. The wheel has a 2-tooth gap
which is used as a reference point for crankshaft position. The engine
speed/reference signal is used to monitor engine RPM and to identify
TDC position of cylinder No. 1.
Hall Effect Sensor
See ELECTRONIC IGNITION SYSTEM under IGNITION SYSTEM in this