8-VALVE 1.4
ENGINE
FIAT PUNTO TRAINING OUTLINE
Fiat Auto S.p.A.
After Sales Training
4.5.15 Engine idling control management
When the optimum temperature is reached, the idling speed management will only depend on
the signal from the engine revs sensor; when external loads are applied, the control unit drives
the throttle control actuator to adjust the engine revs to the conditions that have occurred and
also manage the engine load by sustaining the idling speed.
4.5.17 Fuel vapour recirculation control
The control unit recognizes the idling condition through the accelerator pedal “release”
position. The control unit drives, in order to control the idling speed depending on the devices
turned off and the brake/clutch pedal signals, the power-driven throttle position.
The idling speed envisaged for hot operation is 750 ± 50 r.p.m.
4.5.16 Optimization of thermal operating conditions
The revs number is corrected above all depending on the engine coolant temperature.
This strategy controls the vapour cut-off solenoid valve position as follows:
• during the starting phase, the solenoid valve remains closed, thus preventing the fuel
vapour from excessively enriching the mixture: this condition persists until the engine
coolant temperature reaches 65°C;
• with the engine is thermal condition, the electronic control unit sends the solenoid valve a
square-wave signal (duty-cycle) that modulates its opening.
Thus, the control unit checks the amount of fuel vapour sent to the intake, thus avoiding
significant variations of the mixture ratio.
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