Flow chart
(1) inlet manifold pressure sensor
(2) crankcase breather system
(3) throttle housing heating element
(4) idling regulation stepper motor (1225)
(5) air filter unit
(6) throttle butterfly housing
(7) air temperature sensor
(8) throttle potentiometer
(9) air inlet manifold
(10) petrol injectors (x4)
(11) petrol injector supply rail
(12) petrol vapour recycling circuit (CANISTER)
(13) fuel pressure regulator vacuum circuit (according to model)
Air cleaner
Replacement intervals: every 60 000 km
Throttle butterfly housing
Special features
- Single choke throttle housing
- Reheating of throttle housing by means of an electric resistor
- The canister is bled in the intake manifold (downstream of the throttle) through the canister electrovalve, piloted by the ECU
- The oil vapours are recycled in the inlet manifold: tapping upstream and downstream of the throttle housing
Idling regulation stepper motor (1225)
Role
Operated by the ECU, this component takes control of the air flow by-passing the throttle butterfly housing
In order to
- Provide the supplementary air flow, with engine cold (fast idling)
- Regulate the idling speed according to the engine load, with engine hot
- To provide additional air flow when parking
- Improve the transitory phases of engine operation
Description
The stepper motor converts the electric impulses provided by the injection ECU by moving a plug valve
The plug valve changes its position on the engine axis and alters the amount of air going through the additionnal air duct
NoteThis device allows the presence of a "dash-pot" function
Electrical special features
The stepper motor is directly piloted by the ECU
Allocation of channels of connector
- Channels A and D: 1st winding
- Channels B and C: 2nd winding
Resistance of a winding: 53 ohms
Throttle housing heating element (1270)
Role
The heating resistor prevents the throttle housing from icing up
Description
The sensor consists of a Positive Temperature Coefficient resistor (PTC)
The sensor heating power is controlled according to ambient temperature
12 volts supply
Inlet manifold pressure sensor (1312)
Role
The pressure measuring in the inlet pipe enables the microprocessor to define the amount of air entering the engine in order to meter the amount of petrol
NoteThe density of the air decreases according to the altitude
Description
The sensor consists of stress gauges
The electrical signal transmitted to the ECU by this component varies from 0 to 5 V depending on the pressure recorded
Electrical special features
This component is supplied with 5 V by the ECU
Allocation of channels of connector
- Terminal 1: signal
- Terminal 2: earth
- Terminal 3: + 5 volts supply
Voltage
- 1,6 V for 0,45 bar
- 4,5 V for 1 bar
Location
On the inlet manifold
Catalytic converter
Role
By means of catalysis, the catalytic converter reduces emissions into the atmosphere of the following pollutants
- Carbon monoxide (CO)
- Non-burned hydrocarbons (HC)
- Nitrogen oxides (No.x)
Catalysis is a phenomenon which favours these chemical reactions without requiring the involvement or the combustion of the catalytic converter
Description
Composition of a catalytic converter
- A stainless steel casing
- A thermic insulator
- A ceramic honeycomb core impregnated with precious metals (platinum and rhodium)
To ensure an efficient catalysis, the converter's temperature has to be between 600°C and 800°C
NoteA temperature above 1000°C can lead to its destruction
The catalytic converter's temperature is determined by the air/fuel mixture richness, which requires a very precise regulation through the oxygen sensor, upstream oxygen sensor (1350)
Impregnation of the catalytic converter with precious metals
- Emission control L3: 40 - 50 grammes
- Emission control L4: 65 grammes
WarningIt is essential to use only unleaded fuel to avoid any deterioration of the catalytic converter and of the oxygen sensor