General System Description

Motronic 1.8:

PURPOSE
The Bosch Motronic 1.8 engine control system provides precise control of the fuel injection and ignition systems to ensure optimum performance and strict emissions compliance.

OPERATION
Various engine sensors and other systems (i.e.. air conditioning, auto transmission etc.) supply the control unit with operating information. The control unit processes sensor input and sends output signals to adjust injector pulse width, injector timing, idle speed, and ignition timing.

Input signals include:
^ Engine Speed
^ Reference Mark Signal
^ Air Mass
^ Engine Temperature
^ Cylinder Identification
^ Throttle Position
^ Lambda Signal
^ Battery Voltage
^ Vehicle Speed
^ Gear Position (Auto Trans. only)
^ A/C Signal

Output signals include:
^ Fuel Injection Control
^ Ignition Control
^ Idle Speed Control
^ Fuel Pump Control
^ A/C Compressor Operation
^ Radiator Fan Speed

ON-BOARD DIAGNOSTICS
In the event of a system malfunction, circuit information is stored in the internal memory of the electronic control unit. Intermittent failures are stored with a record of the failure frequency.

The electronic control unit is able to store up to eighteen malfunctions, and will give priority to those items which can cause the vehicle to exceed exhaust emission standards. In addition to being stored in memory, an emissions-related failure will cause the "Check Engine" light to illuminate on the instrument cluster.

ADAPTIVE CONTROL
The electronic control unit has adaptive idle speed, throttle position, and air/fuel mixture capabilities. The control unit continuously compares the programmed data, for idle control and air fuel mixture, with the input values.

If a deviation occurs, the new input values are superimposed and stored in the programmed data map. As a result, new output signals are sent to the idle control valve, and or to the injectors. This allows the electronic control unit to correct the idle speed, or injector pulse width for break-in wear or slight air leaks which might occur in the systems.

If power is interrupted to the control unit, new adaptation takes place within several minutes of engine operation.