Management Of The Engine Idle Control; Starting Stage; Engine Started With Accelerator Pedal Released; Normal Driving - Fiat Bravo/Brava Workshop Manual

Engine Bravo- Btava 9
1 6 v
Fuel system 1999 update
16!
M A N A G E M E N T OF THE ENGINE IDLE CONTROL
The general aim of this strategy is to keep the engine speed around the programmed value (engine warm:
850 rpm): the position assumed by the actuator depends on the engine speed and vehicle speed condi­
tions.
Starting stage
When the key is inserted, the position assumed by the actuator depends on the engine temperature and
the battery voltage (open-loop position).
Engine started w i t h accelerator pedal released
The engine speed varies according to the temperature of the engine and is constantly kept close to this
vaule by altering the position of the shutter to compensate for any fluctuations in the speed.
This takes place especially when external loads are applied (power assisted steering, heated rear wind­
screen, etc.).
If the fans and the air conditioning, both managed by the control unit, are switched on, the strategy man­
ages the actuator in advance of the actual engagement.
Normal driving
In these conditions the actuator is in the open-loop position.
Deceleration
In deceleration conditions outside of idling, the control unit controls the position of the actuator by means
of a special flow rate (dash-pot) curve, in other words it slows down the return of the shutter towards its
housing, thereby reducing the braking effect of the engine.
M A N A G E M E N T OF THE CHARCOAL FILTER SCAVENGING
This strategy controls the position of the charcoal filter solenoid valve in the following way:
- during starting, the solenoid valve remains closed preventing the fuel vapours from enriching the mix­
ture; this condition persists until the engine coolant temperature reaches 25°C;
- with the engine at operating temperature, the control unit operates the solenoid valve in duty-cycle to
control the quantity of fuel vapours sent to the inlet according to the engine speed and load conditions.
In the following operating conditions:
- butterfly in closed position,
- engine speed below 1250 rpm,
- engine load below a pre-set level,
- the operation of the solenoid valve is disabled, keeping it in a closed position.
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