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4C*1
Chapter 4 Part C: Fuel and exhaust systems -
multi-point fuel injection models
Contents
ACAV intake system (1998 cc 16-valve models) - general
Fuel gauge sender unit - removal and refitting 9
information, removal and refitting 19
Fuel injection system - depressurisation 7
Accelerator cable - removal, refitting and adjustment 3
Fuel injection system - testing and adjustment 11
Accelerator pedal - removal and refitting 4
Fuel injection systems - general information 6
Air cleaner assembly and intake ducts - removal and refitting 2
Fuel pump - removal and refitting 8
Air cleaner filter element renewal See Chapter 1
Fuel tank - removal and refitting 10
Bosch Motronic M1.3 system components - removal and refitting . . . 15
General fuel system checks See Chapter 1
Bosch Motronic MP3.1 system components - removal and refitting .. 14
General information and precautions 1
Bosch Motronic MP3.2 system components - removal and refitting .. 16
Idle speed and mixture adjustment See Chapter 1
Bosch Motronic MP5.1 system components - removal and refitting .. 13
Inlet manifold - removal and refitting 18
Exhaust manifold - removal and refitting 20
Magneti Marelli 8P.20 system components - removal and refitting . 17
Exhaust system - general information, removal and refitting 21
Throttle housing - removal and refitting 12
Exhaust system check See Chapter 1
Unleaded petrol - general information and usage 5
Fuel filter - renewal See Chapter 1
Degrees of difficulty
Easy, suitable for
Fairly easy, suitable
Fairly difficult, suitable
Difficult, suitable for
Very difficult,
novice with little
for beginner with
for competent DIY
experienced DIY
suitable for expert DIY
experience
some experience
mechanic
mechanic
or professional
Specifications
System type
1761 cc (LFZ engine) models Bosch Motronic MP5.1
1905 cc non-catalyst (D6E engine) models Bosch Motronic MP3.1
1905 cc catalyst (DKZ engine) models Bosch Motronic M1.3
1998 cc 8-valve (RFX engine) models Magneti Marelli 8P.20
1998 cc 16-valve (RFY engine) models Bosch Motronic MP3.2
Note: Refer to Chapter 2B for further information on engine code identification
Fuel system data
Fuel pump type Electric, immersed in tank
Fuel pump regulated constant pressure (at specified idle speed):
Bosch Motronic systems 2.5 to 3.0 bars (depending on system)
Magneti Marelli system 2.0 bars
Specified idle speed:
1905 cc models 850 50 rpm (adjustable via screw on the throttle housing)
All other models -. 850 50 rpm (not adjustable -controlled by ECU)
Idle mixture CO content:
1905 cc non-catalyst (D6E engine) models 1.0 to 2.0 % (adjustable via screw on mixture adjustment -
potentiometer)
1905 cc catalyst (DKZ engine) models, and all other models Less than 1.0 % (not adjustable- controlled by ECU)
Recommended fuel
Minimum octane rating:
1905 cc non-catalyst (D6E engine) models 95 RON unleaded (UK unleaded premium) or
97 RON leaded (UK "4-star")
1905 cc catalyst (DKZ engine) models, and all other models 95 RON unleaded (UK unleaded premium).
Leaded fuel must not be used

4C*2 Fuel and exhaust systems - multi-point fuel injection models
Torque wrench settings Nm ibf ft
Inlet manifold nuts 22 16
Exhaust manifold nuts 22 16
Exhaust system fasteners:
Front pipe-to-manifold nuts 10 7
Clamping ring nut(s):
Clamps secured with one bolt 25 18
Clamps secured with two bolts 20 15
Warning: Many of the procedures
cleaner-to-throttle housing duct. Slacken the
1 General information and
in this Chapter require the
duct retaining clips, then disconnect it from
precautions
removal of fuel lines and
the air cleaner and throttle housing, and
connections, which may result in some fuel
remove it from the vehicle (see illustrations).
The fuel supply system consists of a fuel
spillage. Before carrying out any operation
Where necessary, recover the rubber sealing
tank (which is mounted under the rear of the
on the fuel system, refer to the precautions
ring from the throttle housing.
car, with an electric fuel pump immersed in it),
given in "Safety first!" at the beginning of
2 Release the two retaining clips, then
a fuel filter, fuel feed and return lines. The fuel
this manual, and follow them implicitly.
slacken and remove the two retaining screws
pump supplies fuel to the fuel rail, which acts
Petrol is a highly-dangerous and volatile
from the front of the cylinder head cover, and
as a reservoir for the four fuel injectors which
liquid, and the precautions necessary when
remove the air cleaner element cover from the
inject fuel into the inlet tracts. The fuel filter
handling it cannot be overstressed.
head. Withdraw the air cleaner element.
incorporated in the feed line from the pump to
Note: Residual pressure will remain in the fuel
3 To remove the intake duct, undo the bolt
the fuel rail ensures that the fuel supplied to
lines long after the vehicle was last used. When
securing the rear section of the duct to the
the injectors is clean.
disconnecting any fuel line, first depressurise
end of the cylinder head, then slacken the
Refer to Section 6 for further information on
the fuel system as described in Section 7.
retaining clip and disconnect the duct from
the operation of each fuel injection system,
the cylinder head cover. Undo the nut
and to Section 21 for information on the
securing the front of the duct to the left-hand
2 Air cleaner assembly and intake
exhaust system. Throughout this Section, it is
wing valance, and manoeuvre the duct out of
ducts - removal and refitting
also occasionally necessary to identify
the engine compartment (see illustration).
vehicles by their engine codes rather than by
1905 cc models
engine capacity alone. Refer to the relevant
Removal
Part of Chapter 2 for further information on
1761 cc and 1998 cc 8-valve models
4 Slacken the retaining clips, and disconnect
engine code identification.
the intake duct and throttle housing duct from
1 Slacken the retaining clip, and disconnect
the air cleaner (see illustration).
the breather hose(s) from the side of the air
5 Slacken and remove the bolt securing the
air cleaner right-hand mounting bracket to the
rear of the cylinder head, and the two nuts
securing the housing to its left-hand mounting
bracket. Lift the air cleaner housing out of the
engine compartment (see illustrations).
6 To remove the intake duct, undo the nut(s)
securing the front of the duct to the left-hand
wing valance, then undo the nut securing the
duct to its mounting bracket (where fitted).
Disconnect the duct from the air cleaner
housing, if not already having done so, and
remove it from the vehicle.
7 On models without a catalytic converter
2.1a On 1761 cc and 1998 cc 8-valve
(Bosch Motronic MP3.1 system), to remove
models, slacken the clips and disconnect
the air cleaner-to-throttle housing duct, first
the hose(s) from the air cleaner-to-throttle
2.1b . . . then slacken the duct retaining
body d u c t . . .
c l i p s . . .
2.4 On 1905 cc models, slacken the
2.1c . . . and remove the duct from the
retaining clips and disconnect the intake
2.3 Intake duct front retaining nut
engine compartment
and throttle housing ducts from the air
c l e a n e r . . .

Fuel and exhaust systems - multi-point fuel injection models 4C*3
of the system operates as follows.
2 The fuel pump (which is immersed in the
fuel tank) supplies fuel from the tank to the
fuel rail, via a filter mounted underneath the
rear of the vehicle. Fuel supply pressure is
controlled by the pressure regulator in the fuel
rail. When the optimum operating pressure of
the fuel system is exceeded, the regulator
allows excess fuel to return to the tank.
3 The electrical control system consists of the
ECU, along with the following sensors:
(a) Throttle potentiometer - informs the ECU
of the throttle position, and the rate of
throttle opening/closing.

2.5a . . . then undo the retaining bolt
2.5b . . . and the two retaining nuts
(b) Coolant temperature sensor - informs the
(arrowed)...
(locations arrowed), then remove the air
ECU of engine temperature.
cleaner housing
(c) Intake air temperature sensor - informs
disconnect the wiring connector from the
the ECU of the temperature of the air
intake air temperature sensor. Slacken the
passing through the throttle housing.
4 Accelerator pedal -
retaining clip, and disconnect the vacuum
(d) Lambda sensor - informs the ECU of the
removal and refitting
pipe from the front of the duct. Slacken the
oxygen content of the exhaust gases
clips, disconnect the duct from the air cleaner
(explained in greater detail in Part D of
Refer to Chapter 4A, Section 8.
and throttle housings, and remove the duct.
this Chapter).
Recover the rubber sealing ring from the
(e) Crankshaft sensor - informs the ECU of
throttle housing.
5 Unleaded petrol - general
the crankshaft position and speed of
8 On models with a catalytic converter
rotation.
information and usage
(Bosch Motronic M1.3 system), the air
(f) Manifold Absolute Pressure (MAP) sensor
cleaner-to-throttle housing duct is in two
Note: The information given in this Chapter is
- informs the ECU of the load on the
sections, with the airflow meter situated in the
correct at the time of writing. If updated
engine (expressed in terms of inlet
middle. Each section can be removed once its
information is thought to be required, check
manifold vacuum).
retaining clips have been slackened, noting
with a Citroen dealer. If travelling abroad,
(g) Vehicle speed sensor - informs the ECU
that, in the case of the front duct section, it
consult one of the motoring organisations (or a
of the vehicle speed.
will also be necessary to disconnect the
similar authority) for advice on the fuel available.
4 All the above signals are analysed by the ECU,
vacuum pipe.
1 The fuel recommended by Citroen is given
and it selects the fuelling response appropriate to
those values. The ECU controls the fuel injectors
1998 cc 16-valve models
in the Specifications Section of this Chapter,
(varying the pulse width - the length of time the
9 Slacken the retaining clip, and disconnect
followed by the equivalent petrol currently on
injectors are held open - to provide a richer or
the air cleaner-to-throttle housing duct from
sale in the UK.
weaker mixture, as appropriate). The mixture is
the throttle housing. Recover the rubber
2 All Citroen ZX multi-point injection models
constantly varied by the ECU, to provide the best
sealing ring. Release the retaining clips, and
are designed to run on fuel with a minimum
setting for cranking, starting (with either a hot or
disconnect the breather hose(s) from the duct.
octane rating of 95 (RON). With the exception
cold engine), warm-up, idle, cruising, and
10 Apply the handbrake, then jack up the
of those 1905 cc models without a catalytic
acceleration.
front of the vehicle and support it on axle
converter (Bosch Motronic MP3.1 system), all
5 The ECU also has full control over the
stands.
models have a catalytic converter, and so
must be run on unleaded fuel only. Under no
engine idle speed, via an auxiliary air valve
11 From underneath the vehicle, slacken and
circumstances should leaded fuel (UK "4-star")
which bypasses the throttle valve. When the
remove the retaining nuts securing the
be used, as this may damage the converter.
throttle valve is closed, the ECU controls the
resonator chamber to the side of the air
However, 1905 cc models without a catalytic
opening of the valve, which in turn regulates
cleaner housing, and remove the chamber.
converter can use either unleaded or leaded
the amount of air entering the manifold, and
12 Undo the air cleaner housing retaining
fuel without modification or risk of damage.
so controls the idle speed.
bolt(s), and remove the housing and duct
6 The ECU also controls the exhaust and
assembly from underneath the vehicle.
3 Super unleaded petrol (98 octane) can also
be used in all models if wished, though there
evaporative emission control systems, which
Refitting
is no advantage in doing so.
are described in detail in Part D of this
13 Refitting is a reversal of the removal
Chapter.
procedure, ensuring that all hoses are
7 An electric heating element is fitted to the
6 Fuel injection systems - general
properly reconnected, and that all ducts are
throttle housing; the heater is supplied with
information
correctly seated and securely held by their
current by the ECU, and warms the throttle
retaining clips.
housing on cold starts to prevent possible
Bosch Motronic MP5.1 system -
icing of the throttle valve.
3 Accelerator cable - removal,
1761 cc models
8 If there is an abnormality in any of the
readings obtained from either the coolant
refitting and adjustment
1 The Bosch Motronic engine management
temperature sensor, the intake air
(fuel injection/ignition) system is fitted to all
temperature sensor or the lambda sensor, the
1 Refer to Chapter 4A, Section 7, substituting
1761 cc models. The system incorporates a
ECU enters its back-up mode. In this event, it
"throttle housing" for all references to the
closed-loop catalytic converter and an
ignores the abnormal sensor signal, and
carburettor. On models with automatic
evaporative emission control system, and
assumes a pre-programmed value which will
transmission, once the accelerator cable is
complies with the very latest emission control
allow the engine to continue running (albeit at
correctly adjusted, check the kickdown cable
standards. Refer to Chapter 5 for information
reduced efficiency). If the ECU enters this
adjustment as described in Chapter 7B.
on the ignition side of the system; the fuel side
back-up mode, the warning light on the

4C*4 Fuel and exhaust systems - multi-point fuel injection models
instrument panel will come on, and the
supply on cold starts and during the
1 The fuel system referred to in this Section is
relevant fault code will be stored in the ECU
warm-up period.
defined as the tank-mounted fuel pump, the
memory.
(c) There is no heating element fitted to the
fuel filter, the fuel injectors, the fuel rail and
9 If the warning light comes on, the vehicle
throttle housing. The engine coolant is
the pressure regulator, and the metal pipes
should be taken to a Citroen dealer at the
circulated around the housing, to warm
and flexible hoses of the fuel lines between
earliest opportunity. A complete test of the
the housing after cold starts.
these components. All these contain fuel
engine management system can then be
Bosch Motronic MP3.2 system -
which will be under pressure while the engine
carried out, using a special electronic
1998 cc 16-valve models
is running, and/or while the ignition is
diagnostic test unit which is simply plugged
switched on. The pressure will remain for
14 The Bosch Motronic MP3.2 engine
into the system's diagnostic connector.
some time after the ignition has been
management (fuel injection/ignition) system is
switched off, and it must be relieved in a
Bosch Motronic MP3.1 system -
fitted to all 1998 cc 16-valve models. Refer to
controlled fashion when any of these
1905 cc models without a catalytic
Chapter 5 for information on the ignition side
components are disturbed for servicing work.
converter
of the system.
2 Disconnect the battery negative terminal.
15 The MP3.2 system is very similar in
10 The Bosch Motronic MP3.1 engine
3 Place a container beneath the
operation to the MP5.1 system described
management (fuel injection/ignition) system is
connection/union to be disconnected, and
above, noting that, in addition to the sensors
fitted to all 1905 cc models without a catalytic
have a large rag ready to soak up any
listed, a camshaft position sensor is
converter (D6E engine). Refer to Chapter 5 for
escaping fuel not being caught by the
incorporated into the system. The camshaft
information on the ignition side of the system.
container.
position sensor is fitted to the left-hand end of
11 The MP3.1 system is very similar in
the cylinder head, directly over the top of the
4 Slowly loosen the connection or union nut
operation to the MP5.1 system described
inlet camshaft, and informs the ECU when
to avoid a sudden release of pressure, and
above, noting the following differences:
No 1 cylinder is at Top Dead Centre (TDC).
position the rag around the connection, to
(a) On the MP3.1 system, there is no lambda
catch any fuel spray which may be expelled.
16 The MP3.2 system differs from all the
(oxygen) sensor or vehicle speed sensor.
Once the pressure is released, disconnect the
other fuel injection systems in that it is a
The idle mixture (exhaust gas CO content)
fuel line. Plug the pipe ends, to minimise fuel
"sequential" system. This means that each of
can be manually adjusted via the mixture
loss and prevent the entry of dirt into the fuel
the four fuel injectors is triggered individually,
adjustment potentiometer.
system.
just before the inlet valve on that particular
(b) The ECU has no control over the engine
cylinder opens. This is in contrast to all other
idle speed; the idle speed is manually set
systems, on which all four injectors are
8 Fuel pump -
using a screw on the throttle housing. An
triggered simultaneously; this happens once
auxiliary air valve (not to be confused with
removal and refitting
for every revolution of the crankshaft.
the idle speed control valve on the MP5.1
system) is incorporated in the system, but

Magneti Marelli 8P.20 system -
Note: Refer to the warning note in Section 1
this is used purely as an additional air
1998 cc 8-valve models
before proceeding.
supply on cold starts and during the
Removal
warm-up period.
17 The Magneti Marelli 8P.20 engine
management (fuel injection/ignition) system is
(c) There is no heating element fitted to the
1 Disconnect the battery negative lead.
fitted to all 1998 cc 8-valve models. Refer to
throttle housing. The engine coolant is
2 For access to the fuel pump, tilt or remove
Chapter 5 for information on the ignition side
circulated around the housing, to warm
the rear seats, as described in Chapter 11.
of the system.
the housing after cold starts.
3 Using a screwdriver, carefully prise the
18 The system is very similar in operation to
(d) There is no evaporative emission control
plastic access cover from the floor, to expose
the Bosch MP5.1 system described above,
system.
the fuel pump (located under the right-hand
apart from the idle speed control system.
cover).
Bosch Motronic Ml.3 system -
19 On the Magneti Marelli system, the idle
4 Disconnect the wiring connector from the
1905 cc models with a catalytic
speed is controlled by the ECU via a stepper
fuel pump, and tape the connector to the
converter
motor fitted to the throttle housing. The motor
vehicle body, to prevent it disappearing
has a pushrod controlling the opening of an
12 The Bosch Motronic M1.3 engine
behind the tank.
air passage which bypasses the throttle valve.
management (fuel injection/ignition) system is
5 Mark the hoses for identification purposes,
When the throttle valve is closed, the ECU
fitted to all 1905 cc models with a catalytic
then slacken the feed and return hose
controls the movement of the motor pushrod,
converter (DKZ engine). Refer to Chapter 5 for
retaining clips. Where the original crimped-
which regulates the amount of air which flows
information on the ignition side of the system.
type Citroen hose clips are fitted, cut the clips
through the throttle housing passage, so
13 The M1.3 system is very similar in
and discard them; use standard worm-drive
controlling the idle speed. The bypass
operation to the MP5.1 system described
hose clips on refitting. Disconnect both hoses
passage is also used as an additional air
above, noting the following differences:
from the top of the pump, and plug the hose
supply during cold starting.
(a) On the M1.3 system, there is no vehicle
ends.
speed sensor or MAP sensor. In place of
6 Noting the alignment marks on the tank,
the MAP sensor, an airflow meter is fitted
pump cover and the locking ring, unscrew the
7 Fuel system - depressurisation
to the throttle housing intake duct, to
ring and remove it from the tank. This is best
inform the ECU of the volume of air
accomplished by using a screwdriver on the
passing through the duct and entering the
Note: Refer to the warning note in Section 1
raised ribs of the locking ring, as follows.
throttle housing.
before proceeding.
Carefully tap the screwdriver to turn the ring
(b) The ECU has no control over the engine
Warning: The following
anti-clockwise until it can be unscrewed by
idle speed; the idle speed is manually set
procedure will merely relieve the
hand.
using a screw on the throttle housing. An
pressure in the fuel system -
7 Displace the pump cover, then reach into the
auxiliary air valve (not to be confused with
remember that fuel will still be
tank and unclip the pump from the tank base.
the idle speed control valve on the MP5.1
present in the system components and
Carefully lift the fuel pump assembly out of the
system) is incorporated in the system, but
take precautions accordingly before
fuel tank, taking care not to damage the filter,
this is used purely as an additional air
disconnecting any of them.
or to spill fuel onto the interior of the vehicle.

Fuel and exhaust systems - multi-point fuel injection models 4C*5
Recover the rubber sealing ring and discard it -
adjustment (exhaust gas CO level) nor the idle
a new one must be used on refitting.
11 Fuel injection system -
speed are adjustable, and should either be
8 Note that the fuel pump is only available as
testing and adjustment
incorrect, a fault must be present in the fuel
a complete assembly - no components are
injection system.
available separately.
Testing
12 Throttle housing -
Refitting
1 If a fault appears in the fuel injection
removal and refitting
9 Ensure the fuel pump pick-up filter is clean
system, first ensure that all the system wiring
and free of debris. Fit the new sealing ring to
connectors are securely connected and free
the top of the fuel tank.
of corrosion. Ensure that the fault is not due to
Removal
10 Carefully manoeuvre the pump assembly
poor maintenance; ie, check that the air
1 Disconnect the battery negative terminal.
into the fuel tank, and clip it into position in
cleaner filter element is clean, the spark plugs
the base of the tank.
are in good condition and correctly gapped,
1761 cc and 1998 cc 8-valve models
11 Align the mark on the fuel pump cover
the cylinder compression pressures are
2 Remove the air cleaner-to-throttle housing
with the centre of the three alignment marks
correct, the ignition timing is correct, and that
duct as described in Section 2.
on the fuel tank, then refit the locking ring.
the engine breather hoses are clear and
3 Disconnect the accelerator inner cable from
Securely tighten the locking ring, and check
undamaged, referring to Chapters 1, 2 and 5
the throttle cam, then withdraw the outer
that the locking ring, pump cover and tank
for further information.
cable from the mounting bracket, along with
marks are all correctly aligned.
2 If these checks fail to reveal the cause of
its flat washer and spring clip (see
12 Reconnect the feed and return hoses to
the problem, the vehicle should be taken to a
illustration).
the top of the fuel pump, using the marks
suitably-equipped Citroen dealer for testing. A
4 Depress the retaining clips, and disconnect
made on removal to ensure they correctly
wiring block connector is incorporated in the
the wiring connectors from the throttle
reconnected, and securely tighten their
engine management circuit, into which a
potentiometer, the electric heating element,
retaining clips.
special electronic diagnostic tester can be
the air temperature sensor and idle control
13 Reconnect the pump wiring connector.
plugged; the connector is located inside either
stepper motor (as applicable) (see
14 Reconnect the battery negative terminal,
the engine compartment junction box, or
illustration).
and start the engine. Check the fuel pump
directly in front of the box (see illustration).
5 Release the retaining clips (where fitted),
feed and return hoses unions for signs of
The tester will locate the fault quickly and
and disconnect all the relevant vacuum and
leakage.
simply, alleviating the need to test all the
breather hoses from the throttle housing (see
15 If all is well, refit the plastic access cover,
system components individually, which is a
illustration). Make identification marks on the
and tilt or refit the rear seat as described in
time-consuming operation that carries a risk
hoses, to ensure they are connected correctly
Chapter 11 (as applicable).
of damaging the ECU.
on refitting.
6 Slacken and remove the three retaining
Adjustment
9 Fuel gauge sender unit -
screws, and remove the throttle housing from
removal and refitting
3 On 1905 cc models without a catalytic
converter (Motronic MP3.1 system), both the
idle speed and idle mixture (exhaust gas CO
Refer to Chapter 4A, Section 5, noting that
level) are adjustable. On 1905 cc models with
there are no fuel pipe connections to the
a catalytic converter (Motronic M1.3 system),
sender unit.
only the idle speed is adjustable (mixture
adjustment is not possible). Refer to Chapter
10 Fuel tank -
1 for information on adjustment procedures.
removal and refitting
4 On all other models, experienced home
mechanics with a considerable amount of skill
Refer to Chapter 4A, Section 6, noting that
and equipment (including a tachometer and
it will be necessary to depressurise the fuel
an accurately calibrated exhaust gas analyser)
system as the feed and return hoses are
may be able to check the exhaust CO level
disconnected (see Section 7). It will also be
and the idle speed. However, if these are
necessary to disconnect the wiring connector
found to be in need of adjustment, the car
11.2 Diagnostic wiring connector located
from the fuel pump before lowering the tank
must be taken to a suitably-equipped Citroen
out of position (see Section 8).
dealer for further testing. Neither the mixture
in the engine compartment junction box
12.3 Disconnecting the accelerator cable -
12.4 Throttle housing wiring connectors
12.5 Throttle housing vacuum hoses
1998 cc 8-valve model
(arrowed) -1761 cc model
(arrowed) - 1761 cc model

4C*6 Fuel and exhaust systems - multi-point fuel injection models
12.7a On 1905 cc models, slacken the
12.7b . . . then disconnect the duct and
retaining clip . . .
12.8a Disconnect the accelerator cable
recover the rubber sealing ring
from the throttle cam . . .
the inlet manifold. Remove the O-ring from the
and remove the throttle housing from the
manifold, and discard it - a new one must be
manifold. On early models, it will also be
used on refitting.
necessary to remove the nut and bolt securing
1905 cc models
the base of the housing to its support bracket
(see illustration). Remove the O-ring from the
7 Slacken the retaining clip, disconnect the
manifold, and discard it - a new one must be
intake duct from the end of the throttle
used on refitting.
housing, and recover the rubber sealing ring
(where fitted) (see illustrations).
1998 cc 16-valve models
8 Disconnect the accelerator inner cable from
13 Slacken the retaining clip, disconnect the
the throttle cam. Slacken and remove the bolt
intake duct from the end of the throttle
and nut securing the outer cable mounting
housing, and recover the rubber sealing ring
bracket to the manifold, then withdraw the
(where fitted).
bracket. Remove the flat washer from the end
14 Disconnect the accelerator inner cable
12.8b . . . then undo the retaining nut and
of the cable for safekeeping (see
from the throttle cam, then withdraw the outer
bolt (arrowed)...
illustrations). On models with automatic
cable from the mounting bracket, along with
transmission, free the kickdown cable from
its flat washer and spring clip.
the throttle cam.
15 Depress the retaining clips, and
9 Depress the retaining clip, and disconnect
disconnect the wiring connectors from the
throttle potentiometer, the electric heating
the wiring connector from the throttle
element, and the air temperature sensor.
potentiometer (see illustration).
16 Slacken the retaining clips (where fitted),
10 Relieve any pressure in the cooling
and disconnect all the relevant vacuum and
system by unscrewing the filler cap. Slacken
breather hoses from the throttle housing.
the retaining clips, and disconnect the two
Make identification marks on the hoses, to
coolant hoses from the base of the throttle
ensure they are connected correctly on
housing. Plug the hose ends, working quickly
refitting.
to minimise coolant loss.
17 Slacken the nut securing the throttle
11 Release the retaining clips (where fitted),
housing lower mounting bracket to the
and disconnect all the relevant vacuum and
transmission housing.
breather hose(s) from the throttle housing
18 Slacken and remove the housing retaining
12.8c . . . and remove the bracket.
(see illustration). Make identification marks
screws, then remove the throttle housing from
Remove the flat washer (arrowed) for
on the hoses, to ensure they are correctly
the inlet manifold. Remove the O-ring from the
safekeeping
reconnected on refitting.
manifold, and discard it - a new one must be
12 Undo the remaining two retaining nuts,
used on refitting.
12.9 Disconnect the throttle potentiometer
12.11 . . . and the breather hose from the
12.12 Undo the two remaining nuts, and
wiring connector . . .
throttle housing
remove the throttle housing

Fuel and exhaust systems - multi-point fuel injection models 4C*7
13.3 Wiring tray retaining bolt (1) and
13.17 Idle speed auxiliary air valve -
13.22 MAP sensor wiring connector (1),
injector wiring connectors (2) - 1761 cc
1761 cc model
vacuum hose (2) and retaining nut (3) -
model
1761 cc model
Refitting
6 Place a wad of clean rag over the injector,
18 Depress the retaining clip, and disconnect
to catch any fuel spray which may be
the wiring connector from the top of the valve.
19 Refitting is a reversal of the removal
released, then carefully ease the relevant
19 Slacken the retaining clip(s), and
procedure, noting the following points:
injector(s) out of the manifold. Remove the O-
disconnect the two hoses from the valve.
(a) Fit a new O-ring to the manifold, then refit
ring from the end of each disturbed injector,
Slide the valve rubber retaining clip off its
the throttle housing and securely tighten
and discard it - these must be renewed
pegs, and remove the valve from the engine
its retaining nuts or screws (as
whenever they are disturbed.
compartment.
applicable).
7 On refitting the injectors, fit a new O-ring to
20 Refitting is a reverse of the removal
(b) Ensure all hoses are correctly
the end of each injector. Apply a smear of
sequence, ensuring that the hoses are
reconnected and, where necessary, are
engine oil to the O-ring, to aid installation,
securely reconnected.
securely held in position by the retaining
then ease the injector(s) back into position in
Manifold absolute pressure (MAP)
clips.
the manifold.
sensor
(c) Ensure all wiring is correctly routed, and
8 Ensure each injector connector is pointing
21 The MAP sensor is situated on the right-
that the connectors are securely
upwards, then refit the retaining plate and
hand side of the engine compartment,
reconnected.
securely tighten its retaining screw.
attached to the engine/transmission mounting
(d) On completion, adjust the accelerator
Reconnect the wiring connector(s) to the
point. To remove the MAP sensor, first
cable as described in Section 3.
injector(s).
disconnect the battery negative terminal.
(e) On 1905 cc models, check the coolant
9 Refit the wiring tray to the top of the
22 Depress the retaining clip, disconnect the
level and top up if necessary (Chapter 1).
manifold, and securely tighten its retaining
wiring connector from the sensor, then
bolts.
disconnect the vacuum hose from the sensor
13 Bosch Motronic MP5.1
10 Refit the air cleaner-to-throttle body duct,
(see illustration).
system components -
and reconnect the battery. Start the engine,
23 Undo the retaining bolt, and remove the
removal and refitting
and check the injectors for signs of leakage.
sensor from the engine compartment.
24 Refitting is a reverse of the removal
Fuel pressure regulator
Note: Check parts availability with a Citroen
procedure.
dealer prior to removing individual components.
11 Refer to Section 14.
Coolant temperature sensor
At the time of writing, certain components are
Throttle potentiometer
25 Refer to Chapter 3, Section 6.
only available as part of a larger assembly - eg
the throttle potentiometer is only available as

12 The throttle potentiometer is fitted to the
Intake air temperature sensor
part of the throttle housing assembly.
right-hand side of the throttle housing. To
26 The intake air temperature sensor is
remove the potentiometer, first disconnect the
located in the throttle housing (see
Fuel injectors
battery negative terminal.
illustration).
Note: Refer to the warning note in Section 1
13 Depress the retaining clip, and disconnect
before proceeding. If a faulty injector is
the potentiometer wiring connector.
suspected, before condemning the injector, it
14 Slacken and remove the two retaining
is worth trying the effect of one of the
screws, and remove the potentiometer from
proprietary injector-cleaning treatments.
the throttle housing.
1 Disconnect the battery negative terminal.
15 Refitting is the reverse of removal,
2 Remove the air cleaner-to-throttle housing
ensuring that the potentiometer is correctly
duct as described in Section 2.
engaged with the throttle valve spindle.
3 Undo the two bolts securing the wiring tray
Electronic Control Unit (ECU)
to the top of the manifold, and position the
tray clear of the injectors (see illustration).
16 Refer to Section 17.
4 Depress the retaining clip(s), and
Idle speed auxiliary air valve
disconnect the wiring connector(s) from the
injector(s).
17 The idle speed auxiliary air valve is
5 Slacken the retaining screw, and remove
mounted on the left-hand end of the cylinder
13.26 On 1761 cc models, the intake air
the injector retaining plate; Nos 1 and 2
head, directly above the ignition HT coil (see
temperature sensor (arrowed) is situated
injectors are retained by one plate, Nos 3 and
illustration). To remove the valve, first
behind the throttle potentiometer
4 by another.
disconnect the battery negative terminal.

4C*8 Fuel and exhaust systems - multi-point fuel injection models
14.3 Where original crimped-type Citroen
14.4 Disconnecting the injector wiring
hose clips are fitted, cut them and discard
14.5 On 1905 cc models, the fuel rail is
connectors -1905 cc model
retained by two bolts (arrowed)
27 To remove the sensor, first remove the
Section 7, slacken the retaining clips, and
throttle potentiometer as described in
Fuel pressure regulator
disconnect the fuel feed and return hoses
paragraphs 12 to 14.
from the either end of the fuel rail. Where the
Note: Refer to the warning note in Section 1
28 Depress the retaining clip, and disconnect
original crimped-type Citroen hose clips are
before proceeding.
the wiring connector from the air temperature
still fitted, cut them off and discard them; use
8 Disconnect the vacuum pipe from the
sensor.
standard worm-drive hose clips on refitting
regulator.
29 Remove the screw securing the sensor
(see illustration).
9 Place a wad of clean rag over the regulator,
connector to the top of the throttle housing,
4 Depress the retaining tangs, and
to catch any fuel spray which may be
then carefully ease the sensor out of position
disconnect the wiring connectors from the
released. Remove the retaining clip, and slide
and remove it from the throttle housing.
four injectors (see illustration).
the regulator out of the end of the fuel rail (see
Examine the sensor O-ring for signs of
5 Slacken and remove the two fuel rail
illustration).
damage or deterioration, and renew if
retaining bolts, then carefully ease the fuel rail
10 Refitting is a reversal of the removal
necessary.
and injector assembly out from the inlet
procedure. Examine the regulator seal for
30 Refitting is a reversal of the removal
manifold and remove it from the vehicle (see
signs of damage or deterioration, and renew if
procedure, using a new O-ring where
illustration). Remove the O-rings from the
necessary.
necessary, and ensuring that the throttle
end of each injector, and discard them; these
potentiometer is correctly engaged with the
must be renewed whenever they are
Throttle potentiometer
throttle valve spindle.
disturbed.
11 Disconnect the battery negative terminal.
Crankshaft sensor
6 Slide out the retaining clip(s), and remove
12 Depress the retaining clip, and disconnect
the relevant injector(s) from the fuel rail.
the wiring connector from the throttle
31 Refer to Section 14.
Remove the upper O-ring from each injector
potentiometer.
as it is removed, and discard it; all O-rings
13 Slacken and remove the two retaining
Fuel injection system relay unit
must be renewed once they have been
screws, then disengage the potentiometer
32 Refer to Section 14.
disturbed.
from the throttle valve spindle and remove it
7 Refitting is a reversal of the removal
from the vehicle (see illustration).
Throttle housing heating element
procedure, noting the following points:
14 Refitting is a reverse of the removal
33 Refer to Section 17.
(a) Fit new O-rings to all disturbed injectors.
procedure, ensuring that the potentiometer is
(b) Apply a smear of engine oil to the O-rings
correctly engaged with the throttle valve
to aid installation, then ease the injectors
spindle (see illustration).
14 Bosch Motronic MP3.1
and fuel rail into position, ensuring that
system components -
none of the O-rings are displaced.
Electronic Control Unit (ECU)
removal and refitting
(c) On completion, start the engine and
15 The ECU is located in the rear left-hand
check for fuel leaks.
corner of the engine compartment. To remove
Note: Check parts availability with a Citroen
dealer prior to removing individual
components. At the time of writing, certain
components are only available as part of a

larger assembly - eg the throttle potentiometer
is only available as part of the throttle housing
assembly.

Fuel rail and injectors
Note: Refer to the warning note in Section 1
before proceeding. If a faulty injector is
suspected, before condemning the injector, it

is worth trying the effect of one of the
proprietary injector-cleaning treatments.
1 Disconnect the battery negative terminal.
2 Disconnect the vacuum pipe from the fuel
14.9 Fuel pressure regulator retaining clip
14.13 Throttle potentiometer is secured to
pressure regulator.
(arrowed) can be prised out of position
the throttle housing by two screws
3 Bearing in mind the information given in
using a flat-bladed screwdriver

Fuel and exhaust systems - multi-point fuel injection models 4C*9
14.14 On refitting, ensure that the
potentiometer is correctly engaged with 14.17a Undo the ECU upper retaining
14.17b . . . and loosen its lower mounting
the throttle valve spindle (arrowed) b o l t . . .
nut. The lower mounting is slotted to ease
removal
the ECU, first disconnect the battery negative
the idle mixture setting (exhaust gas CO level)
terminal.
as described in Chapter 1.
16 Depress the retaining clip, and disconnect
Auxiliary air valve
the wiring connector from the idle mixture
adjustment potentiometer.
23 The auxiliary air valve is mounted on the
left-hand end of the cylinder head, directly
17 Slacken and remove the upper bolt
beneath the ignition HT coil (see illustration).
securing the ECU mounting bracket to the
24 To improve access to the valve, remove
wing valance, then loosen the lower bolt
the ignition HT coil as described in Chapter 5.
(there is no need to remove the lower bolt, as
25 Depress the retaining clip, and disconnect
the mounting is slotted). Withdraw the bracket
the wiring connector from the air valve.
and ECU assembly from the engine
26 Slacken the retaining clips, and
compartment, disconnecting the wiring
disconnect the vacuum hoses from either end
connector and vacuum pipe from the ECU as
of the auxiliary air valve.
they become accessible (see illustrations).
27 Undo the two retaining bolts, and remove
18 With the assembly on the bench, undo the
the auxiliary air valve from the engine
14.17c Remove the ECU, disconnecting its
bolts securing the ECU to the bracket, and
compartment.
vacuum hose (1) and wiring connector (2)
separate the two components.
28 Refitting is a reversal of the removal
as they become accessible
19 Refitting is a reversal of the removal
procedure.
procedure, ensuring that the wiring connector
and vacuum pipe are securely reconnected.
Manifold absolute pressure (MAP)
sensor

Idle speed mixture adjustment
potentiometer
29 The MAP sensor is an integral part of the
electronic control unit (ECU). Refer to
20 The idle speed mixture adjustment
paragraphs 15 to 19 for removal and refitting
potentiometer is situated in the rear left-hand
details.
corner of the engine compartment, mounted
onto the ECU bracket. To remove it, first
Coolant temperature sensor
disconnect the battery negative terminal.
30 Refer to Chapter 3, Section 6.
21 Depress the retaining tangs and
disconnect the wiring connector, then undo the
Intake air temperature sensor
retaining screw and remove the potentiometer
31 The intake air temperature sensor is
from the vehicle (see illustrations).
located in the air cleaner-to-throttle housing
22 Refitting is the reverse of removal. On
duct (see illustration). To remove the sensor,
14.21a Disconnect the wiring
completion, check and, if necessary, adjust
first disconnect the battery negative terminal.
connector...
14.21b . . . then undo the retaining screw
and remove the idle speed mixture
14.23 Auxiliary air valve location - wiring
14.31 Disconnecting the wiring connector
potentiometer
connector arrowed
from the intake air temperature sensor

4C*10 Fuel and exhaust systems - multi-point fuel injection models
32 Disconnect the wiring connector, then
unscrew the sensor from the intake duct and
remove it from the vehicle.
33 Refitting is the reverse of removal.
Crankshaft sensor
34 The crankshaft sensor is mounted on top
of the transmission housing, next to the left-
hand end of the cylinder block. To remove the
sensor, first disconnect the battery negative
terminal.
35 Access to the sensor is poor, and it will be
necessary to remove the battery and battery
tray (see Chapter 5) and/or the intake duct
14.39a Disconnect the wiring
14.39b . . . then undo the retaining bolt,
assembly (see Section 2) to improve access
connector...
and remove the fuel injection relay unit
(depending on model and specification). On
from the front of the junction box
some models, it will also be necessary to
remove the metal plate from the top of the
Throttle switch
18 Undo the two retaining bolts, and remove
transmission housing; the plate is retained by
the auxiliary air valve from the engine
one of the engine-to-transmission bolts, and
3 Disconnect the battery negative terminal.
compartment.
by a second bolt securing the plate to the top
4 Depress the retaining clip, and disconnect
19 Refitting is a reversal of the removal
of the transmission.
the wiring connector from the throttle
procedure.
potentiometer.
36 Trace the wiring back from the sensor to
5 Slacken and remove the two retaining
Manifold absolute pressure (MAP)
its wiring connector, and disconnect it from
screws, then disengage the potentiometer
sensor
the main wiring harness. Undo the retaining
from the throttle valve spindle and remove it
bolt, and remove the sensor from the top of
20 Refer to Section 14.
from the vehicle.
the transmission housing.
6 When refitting the switch, ensure it is
Coolant temperature sensor
37 Refitting is a reversal of the removal
correctly engaged with the throttle valve
procedure, ensuring that the sensor wiring is
21 Refer to Chapter 3, Section 6.
spindle, and lightly tighten its retaining
correctly routed.
screws. Slowly operate the throttle valve
Intake air temperature sensor
Fuel injection system relay unit
whilst listening to the switch; the switch
22 The intake air temperature sensor is an
should click as soon as the throttle valve
38 The fuel injection system relay unit is
integral part of the airflow meter, and is not
starts to open, and again just before it is fully
mounted on the front of the engine
available separately. Refer to paragraphs 9
closed. Position the switch until this is so,
compartment junction box. To remove the
to 13 for airflow meter removal and refitting
then securely tighten its retaining screws.
relay unit, first disconnect the battery negative
details.
7 Reconnect the wiring connector, and
terminal.
reconnect the battery.
Crankshaft sensor
39 Open up the junction box lid, then slacken
and remove the relay mounting nut and
Electronic Control Unit (ECU)
23 Refer to Section 14.
washer. Release the retaining clip, then
8 Refer to the information given in Section 14,
Fuel injection system relay unit
disconnect the wiring connector and remove
noting that there is no idle mixture adjustment
24 Refer to Section 14.
the relay unit from the engine compartment
potentiometer to disconnect.
(see illustrations).
Airflow meter
40 Refitting is the reverse of removal.
16 Bosch Motronic MP3.2
9 Disconnect the battery negative terminal.
system components -
10 Depress the retaining clip, and disconnect
removal and refitting
the wiring connector from the airflow meter.
15 Bosch Motronic M1.3 system
11 Slacken the retaining clips, and
Note: Check parts availability with a Citroen
components -
disconnect the intake ducts from either end of
dealer prior to removing individual
removal and refitting
the airflow meter.
components. At the time of writing, certain
12 Slacken and remove the retaining nuts
components are only available as part of a
Note: Check parts availability with a Citroen
and bolts, and remove the airflow meter from
larger assembly, eg the throttle potentiometer
dealer prior to removing individual
the engine compartment.
is only available as part of the throttle housing
components. At the time of writing, certain
13 Refitting is a reverse of the removal
assembly.
components are only available as part of a
procedure.
larger assembly, eg the throttle switch is only
Fuel rail and injectors
available as part of the throttle housing
Auxiliary air valve
Note: Refer to the warning note in Section 1
assembly.
14 The auxiliary air valve is mounted on the
before proceeding. If a faulty injector is
left-hand end of the cylinder head, directly
Fuel rail and injectors
suspected, before condemning the injector, it
beneath the airflow meter.
is worth trying the effect of one of the
1 The fuel rail and injectors can be removed
15 To improve access to the valve, remove
proprietary injector-cleaning treatments.
as described in Section 14, noting that it will
the airflow meter as described above.
1 Disconnect the battery negative terminal.
first be necessary to remove the ignition HT
16 Depress the retaining clip, and disconnect
2 Disconnect the vacuum pipe from the fuel
coil as described in Chapter 5.
the wiring connector from the air valve.
pressure regulator.
17 Slacken the retaining clips, and
3 Bearing in mind the information given in
Fuel pressure regulator
disconnect the vacuum hoses from either end
Section 7, slacken the retaining clips, and
2 Refer to Section 14.
of the auxiliary air valve.
disconnect the fuel feed and return hoses