Peugeot 405. Manual - part 35

6 Connect an exhaust gas analyser to the
vehicle in accordance with the manufacturer’s
instructions.
7 Start the engine and allow it to idle. Turn
the mixture adjustment screw in or out to
obtain the specified CO content (see
illustration).
8 Re-adjust the idle speed as previously
described.
9 On completion, stop the engine, remove all
test equipment and fit a new tamperproof cap
to the screw.

Bosch ML4.1 system

10 The idle speed is non-adjustable. It is
controlled by the idle speed regulator valve.
11 To check the mixture (CO), first ensure
that the conditions in paragraph 3 are met.
12 Connect an exhaust gas analyser to the
vehicle in accordance with the manufacturer’s
instructions.
13 Remove the tamperproof cap from the
mixture adjustment screw on the airflow meter
housing.
14 Turn the screw clockwise to increase and
anti-clockwise to decrease CO content until
the specified CO level is obtained.
15 Remove all test equipment and fit a new
tamperproof plug to the screw.

Bosch LU2-Jetronic system

16 Idle speed is adjusted as described for
the Bosch L3.1 system (see illustration).

17 Idle mixture is not adjustable, and is
automatically regulated by the electronic
control unit according to signals provided by
the oxygen sensor.

Bosch Motronic M1.3 system

18 Idle speed is only adjustable on 8-valve
engines; on 16-valve engines it is controlled
by the ECU. On 8-valve engines use the
procedure given in paragraphs 3 and 4.
19 Adjustment of idle mixture is as given in
paragraphs 5 to 9.

MM8P, Sagem-Lucas 4GJ, 
Bosch Motronic 5.1, 
Bosch Motronic 3.2 systems

20 Experienced home mechanics with a
considerable amount of skill and equipment
(including a tachometer and an accurately
calibrated exhaust gas analyser) may be able
to check the exhaust CO level and the idle

speed. However, if these are found to be in
need of adjustment, the car must be taken to
a suitably-equipped Peugeot dealer for further
testing. Neither the mixture adjustment
(exhaust gas CO level) nor the idle speed are
adjustable, and should either be incorrect, a
fault must be present in the fuel injection
system.

12 Throttle housing - 

removal and refitting

2

Note: At the time or writing no information
was available for the Sagem-Lucas system.

Removal

1 Disconnect the battery negative terminal.

Bosch Jetronic system

2 Remove the airflow meter with reference to
Section 2.
3 Disconnect the accelerator cable from the
throttle housing.
4 Either drain the cooling system or clamp
the coolant hoses as close as possible to the
throttle housing, then disconnect the coolant
inlet hose (see illustration).
5 Disconnect the throttle switch wiring multi-
plug (see illustration).
6 Loosen the clip and detach the plastic duct
from the throttle housing (see illustration).
7 Disconnect the coolant return hose,
distributor vacuum hose and breather hose
from the throttle housing (see illustration).

Fuel/exhaust systems - multi-point fuel injection models  4C•5

11.16  Idle speed adjustment screw (2)

(LU2-Jetronic system)

12.7  Disconnect the coolant return (A),

distributor vacuum hose (B) 

and breather hose (C)

12.6  Detach the plastic duct

12.5  Disconnecting the multi-plug

12.4  Disconnecting the coolant inlet hose

4C

11.4  Adjusting the idle speed screw on the

Bosch L3.1 system

11.7  Mixture (CO ) adjustment screw on

the airflow meter (Bosch L3.1 system)

8 Unscrew the Allen bolts and remove the
throttle housing (see illustration).

Bosch LU2-Jetronic system

9 Release the securing clip, and disconnect
the wiring plug from the throttle position
switch.
10 Loosen the securing clamp, and
disconnect the air trunking from the front of
the throttle body.
11 Disconnect the accelerator cable.
12 Disconnect the vacuum and/or breather
hoses from the throttle body, noting their
locations to ensure correct refitting.
13 Unscrew the three throttle body securing
nuts, and recover the washers. Remove the
throttle cable bracket from the top throttle
body securing stud, noting its orientation.

Bosch Motronic system

14 Slacken the retaining clip, then
disconnect the inlet duct from the throttle
housing and recover the sealing ring.
15 Disconnect the accelerator inner cable
from the throttle cam, then withdraw the outer
cable from the mounting bracket, along with
its flat washer and spring clip.
16 Depress the retaining clip and disconnect
the wiring connector(s) from the throttle
potentiometer, and, where necessary, from
the electric heating element, the air
temperature sensor.
17 Slacken and remove the three retaining
screws and remove the throttle housing from
the inlet manifold. Recover the O-ring from
manifold and discard it; a new one must be
used on refitting.

Magneti Marelli 8P system

18 Remove the air cleaner-to-throttle
housing duct as described in Section 2.
19 As applicable, carefully lever the
accelerator linkage rod off its throttle housing
balljoint, or disconnect the accelerator inner
cable from the throttle cam, then withdraw the
outer cable from the mounting bracket along
with its flat washer and spring clip. Where
necessary, also disconnect the kickdown
cable as described in Chapter 7B (see
illustration).
20 Depress the retaining clips, and
disconnect the wiring connectors from the
throttle potentiometer, the electric heating
element, the air temperature sensor and idle
control stepper motor (as applicable).
21 Release the retaining clips (where fitted),
and disconnect all the relevant vacuum and
breather hoses from the throttle housing. Make
identification marks on the hoses, to ensure
they are connected correctly on refitting.
22 Slacken and remove the three retaining
screws, and remove the throttle housing from
the inlet manifold. Remove the O-ring from the
manifold, and discard it - a new one must be
used on refitting.

Refitting

23 Refitting is a reversal of the removal
procedure, noting the following points:

a) Fit a new O-ring to the manifold, then refit

the throttle housing and securely tighten
its nuts or screws (as applicable).

b) Ensure all hoses are correctly reconnected

and, where necessary, are securely held in
position by the retaining clips.

c) Ensure all wiring is correctly routed, and

the connectors are securely reconnected.

d) On completion, adjust the accelerator

cable as described in Section 3 and,
where necessary, the kickdown cable as
described in Chapter 7B.

13 Electronic control unit -

removal and refitting

3

Removal

1 With the exception of the Bosch L3.1-
Jetronic system, the electronic control unit is

located behind the engine compartment
bulkhead on the left-hand side. On the L3.1
system it is located on the air cleaner cover
and is removed by removing the cover as
described in Section 2. Proceed as follows for
other models.
2 To remove the unit first disconnect the
battery negative lead.
3 Open the bonnet and unclip the cover from
the top of the engine compartment bulkhead.
4 Release the clip, and disconnect the wiring
plug from the electronic control unit.
5 Unscrew the clamp bolts or nuts, as
applicable, securing the ECU to the housing,
then carefully withdraw the unit from its
location. On some models, it may be
necessary to disconnect the control unit
wiring harness earth lead before the unit can
be withdrawn.
6 Where applicable, separate the control unit
from its mounting bracket.

Refitting

7 Refitting is a reversal of removal,  ensuring
that the wiring harness earth lead is correctly
reconnected where applicable.

14 Bosch L3.1-Jetronic system

components - removal,
refitting and adjustments

3

Throttle initial position

1 Disconnect the accelerator cable and
throttle switch.
2 Loosen the throttle switch unit mounting
bolts and turn the unit fully anti-clockwise,
then tighten the mounting bolts.

Primary barrel

3 Prise out the tamperproof cap from the
throttle stop screw and loosen the screw until it
is clear of the throttle lever (see illustration).
4 Place a 0.05 mm feeler blade between the
lever and the screw and tighten the screw
until it just contacts the feeler blade without
trapping it (see illustration). The throttle lever
must not be moved.

14.4  Adjusting the throttle initial position

4C•6 Fuel/exhaust systems - multi-point fuel injection models

12.8  Removing the throttle housing

14.3  Tamperproof cap covering primary

throttle stop screw (arrowed)

12.19  Accelerator cable and kickdown

cable connections on the throttle housing

(Magneti Marelli 8P fuel injection system)

5 Remove the feeler blade then turn the
screw in by a further quarter turn. Fit a new
tamperproof cap.

Secondary barrel

6 The procedure is as described for the
primary barrel but using the secondary throttle
adjustment screw (see illustrations).
7 On completion of the adjustment, apply a
drop of thread locking compound to the head
of the adjustment screw.
8 Adjust the throttle switch.
9 Reconnect the throttle switch and
accelerator cable.

Throttle switch

10 To remove the unit, disconnect the multi-
plug and unbolt the unit from the throttle
housing.
11 To adjust the switch proceed as follows.
12 The throttle valve initial opening position
must be correctly adjusted.

Idling switch

13 Loosen the switch bolts and turn it
clockwise as far as it will go, then bring it back
until the switch can be heard to operate (see
illustration).
14 Tighten the mounting bolts with the
switch held in this position.
15 To check that the adjustment is correct,
disconnect the multi-plug and connect an
ohmmeter to terminals 2 and 18 on the
switch.
16 The ohmmeter should read zero ohms.
17 Fully depress the accelerator pedal, when
the ohmmeter should read infinity.
18 If these readings are incorrect, re-adjust
the switch.

Full load switch

19 Connect the ohmmeter to terminals 3 and
18 on the switch. The reading should indicate
infinity.
20 Fully depress the accelerator pedal, when
the reading should be zero ohms.
21 If these readings are incorrect, renew the
throttle switch.
22 Reconnect the multi-plug.

Airflow meter and ECU

23 The airflow meter and ECU are removed
as described in Section 2.

Fuel rail and injectors

Note: Refer to the warning note in Section 1
before proceeding.
Note: If a faulty injector is suspected, before
condemning the injector, it is worth trying the
effect of one of the proprietary injector-
cleaning treatments.
24 Depressurise the fuel system.
25 Disconnect the sensor pipe on the fuel
pressure regulator and remove the bolt from
the regulator support bracket on the inlet
manifold.
26 Number the injector electrical plugs then
disconnect them from the injectors.
27 Disconnect the inlet and outlet fuel hoses,
being prepared for any fuel spillage.
28 Unbolt the fuel rail and pull it and the
injectors upward to release them from the
cylinder head (see illustrations).
29 Pull out the clips securing the injectors to

the fuel rail and pull out the injectors. Number
them for refitting in the same positions (see
illustration).
30 Check the condition of the O-ring seals
and renew them as necessary (see
illustration).
31 Clean the injector nozzles using injector
cleaning fluid. Note: Fouling of the injector
nozzles can cause the following symptoms.

a) Difficult hot starting.
b) Persistent stalling.
c) Misfiring when cold.
d) Misfire when hot between 1000 and 

2000 rpm.

e) Loss of performance.

32 Refitting is a reversal of removal.

Fuel pressure regulator

33 Depressurise the system.
34 Disconnect the sensor pipe.
35 Disconnect the fuel hose.

Fuel/exhaust systems - multi-point fuel injection models  4C•7

14.13  Throttle switch unit mounting bolts

(A) and plug terminal numbers

14.29  Removing an injector 

from the fuel rail

14.28b  . . . and pulling up the rail and

injectors

14.28a  Removing a fuel rail bolt . . .

14.6b  . . . and viewed from underneath

14.6a  Secondary throttle adjusting screw

(arrowed) . . .

4C

14.30  Injector O-ring seals (arrowed)

36 Remove the bolt from the support bracket
on the inlet manifold.
37 Unbolt and remove the regulator from the
fuel rail (see illustration).
38 Refit in reverse order.

Fuel pump damper

39 Depressurise the fuel system.
40 Disconnect the fuel hose unions from the
damper (see illustration).
41 Unscrew the nut securing the damper to
the support bracket and remove the damper.
42 Refit in reverse order.

Supplementary air device

43 Disconnect the battery then remove the
battery and battery tray.
44 Remove the nuts securing the water
housing to the cylinder head.
45 Disconnect the wiring and air hoses from
the air device (see illustration).
46 Tilt the water housing to gain access to
the air device securing bolts and remove the
bolts and air device.
47 Refit in reverse order.

Injection thermistor

48 Disconnect the wiring from the thermistor
on the water housing (see illustration).
49 Drain the cooling system.
50 Unscrew the thermistor from the water
housing.
51 Refit in reverse order, using a new sealing
washer.
52 Top-up and bleed the cooling system.

Fuel filter

53 Disconnect the battery negative lead.
54 Depressurise the fuel system.
55 Disconnect the inlet and outlet hoses from
the filter (see illustration).
56 Loosen the rubber mounting strap clamp
nut and slide the filter from the clamp.
57 Refit in reverse order, ensuring any
directional arrows on the filter are facing the
direction of fuel flow.

15 Bosch LU2-Jetronic system

components - removal,
refitting and adjustments

3

Throttle initial position

1 The throttle initial position is set in
production, and will not normally require
adjustment unless the throttle housing has
been tampered with. Adjustment should be
entrusted to a Peugeot dealer.

Throttle switch unit

2 Disconnect the battery negative lead.
3 Disconnect the wiring plug from the switch.
4 Remove the two securing screws, and
withdraw the switch from the throttle body.
5 Commence refitting by initially adjusting the
switch as described later.
6 Refitting is reversal of removal, but ensure
that the switch wiper engages correctly with
the flats on the end of the throttle spindle.
7 The throttle initial position must be correctly

adjusted before attempting to adjust the
throttle switch.
8 Slacken the throttle switch securing screws.
9 Turn the switch unit fully clockwise, then
turn it slowly back until the idling contacts are
heard to close.
10 Tighten the securing screws.
11 Pull the wiring from the switch, then
connect an ohmmeter between terminals 2
and 18 in the switch - the ohmmeter should
read zero.
12 Operate the throttle linkage, and the
ohmmeter should read infinity.
13 If the readings are not correct, repeat the
adjustment.
14 Connect an ohmmeter between switch
terminals 3 and 18 - the ohmmeter should
read infinity.
15 Fully open the throttle, and the ohmmeter
should read zero.
16 If the specified readings cannot be
obtained, renew the switch.
17 Reconnect the switch wiring plug on
completion.

Airflow meter

18 The airflow meter is removed as
described in Section 2.

Electronic control unit (ECU)

19 Refer to Section 13.

Fuel injectors

Note: Refer to the warning note in Section 1
before proceeding.
Note: If a faulty injector is suspected, before
condemning the injector, it is worth trying the
effect of one of the proprietary injector-
cleaning treatments.
20 Depressurise the fuel system.
21 Disconnect the battery negative lead.
22 Disconnect the wiring plugs from the fuel
injectors, labelling them if necessary to ensure
correct refitting.
23 Disconnect the vacuum hose from the top
of the fuel pressure regulator.
24 Unscrew the four bolts securing the fuel
rail to the inlet manifold then carefully lift the
rail, complete with pressure regulator and fuel
injectors, from the inlet manifold, taking care
not to strain any of the hoses or pipes.

4C•8 Fuel/exhaust systems - multi-point fuel injection models

14.37  Regulator-to-fuel rail bolts (arrowed)

- assembly removed for clarity

14.45  Disconnecting the supplementary

air device plug

14.55  Fuel filter showing fuel hoses (A)

and clamp bolt (B)

14.48  Disconnecting the injection

thermistor wiring

14.40  Fuel pump damper showing fuel

hose connections