Engine idle control

ENGINE IDLE CONTROL

The main aim of this strategy is to maintain engine speed at around the mapped setting (warm engine: 850 rpm): the position assumed by the actuator is dependent on engine conditions/rpm and vehicle speed.

Start-up stage

When the key is inserted, the actuator takes up a position dependent on engine temperature and battery voltage (open-loop position).

Warming-up stage

The rpm is mainly corrected on the basis of coolant temperature.

With the engine warm, idle management is dependent upon the signal from the rpm sensor. The ECU introduces sustained idle when external loads are activated.

Deceleration stage

When the accelerator is released when the car is not idling, the ECU governs the actuator (step motor) by measn of special delivery curve (dash-pot curve), i.e. delays the return of the plunger to its housing to bring about a reduction in engine braking effect.

FUEL VAPOUR RECIRCULATION MANAGEMENT

The strategy controls vapour cut-off solenoid position as follows:

• during start-up, the solenoid remains closed to prevent fuel vapours enriching the mixture excessively. This condition persists until coolant temperature reaches 65° C;
• with the engine warm, the ECU sends the solenoid a square wave signal (duty-cycle control) which modulates opening.

In this way, the ECU controls the amount of fuel vapour directed to the intake, thus avoiding substantial changes in mixture concentration.

Under the following operation conditions:

• throttle valve closed
• speed less than 1500 rpm
• intake manifold pressure less than a lower threshold calculated by the ECU in accordance with rpm level

solenoid control is inhibited with the same closure position maintained. This makes engine operation more efficient.

TEST MANAGEMENT

Full injection-ignition system electronic testing can be achieved by connecting a FIAT/LANCIA TESTER to the test socket.

The system is also equipped with a self-diagnostic function which recognises, memorises and indicates any faults.

If sensors or actuators are found to be faulty, signal reconstruction strategies are immediately activated (recovery) so that the engine is able to operate at an acceptable level without affecting function. The car can then be driven to a service point for the necessary repairs.