1988 OPEL CALIBRA coolant

Idle settings (continued)
Idle mixture (CO content):
20 NE and 20 SEH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.0 max.
20 XEJ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0.7 to 1.2%
All other models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0.3 % (at 2800 to 3200 rpm)
Fuel Pressure (regulator vacuum hose connected)
Multec . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0.76 bar
Motronic 4.1:
Feed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.3 to 2.7 bar
Return . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0.3 to 1.5 bar
Motronic 1.5:
Feed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.8 to 2.2 bar
Return . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0.3 to 1.5 bar
Motronic 2.5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.0 to 2.2 bar
Motronic 2.8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.2 to 2.7 bar
Simtec 56.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .not available
Torque wrench settingsNmlbf ft
All specifications as for carburettor models except for the following:
Bracket, tank vent valve to coolant flange . . . . . . . . . . . . . . . . . . . . . . .86
Fuel distributor pipe to inlet manifold . . . . . . . . . . . . . . . . . . . . . . . . . . .86
Fuel flow damper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2015
Fuel injector retainer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32
Fuel pressure regulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.52
Fuel pump clamp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43
Idle air control stepper motor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.52
Knock sensor (X16 SZ) to block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1310
Oxygen sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3022
Throttle body mounting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2015
Throttle body upper-to-lower section . . . . . . . . . . . . . . . . . . . . . . . . . . .64.5
Throttle potentiometer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21.5
Throttle valve housing to inlet manifold . . . . . . . . . . . . . . . . . . . . . . . . .97
1General description
General
1All engines available within the Cavalier
range can be operated on unleaded petrol.
Refer to Chapter 5 for further details. Note
that models fitted with a catalytic converter
must only be operated on unleaded petrol,
and leaded petrol must not be used. Models
with catalytic converter can be identified by
the engine code, which is prefixed by the
letter ‘C’ or ‘X’.
Multec system
Note: There is no provision for the adjustment
or alteration of the idle speed; if checking the
idle speed, remember that it may vary
constantly under ECU control.
2The Multec system is essentially a simple
method of air/fuel metering, replacing the
carburettor with a single injector mounted in a
throttle body. This type of system is therefore
also known as Throttle Body Injection (TBi),
Central Fuel Injection (CFi) or single-(or
mono-) point injection. The whole system is
best explained if considered as three
sub-systems, these being fuel delivery, air
metering and electrical control.
3The fuel delivery system incorporates the
fuel tank (with the electric fuel pumpimmersed inside it), the fuel filter, the fuel
injector and pressure regulator (mounted in
the throttle body), and the hoses and pipes
connecting them. When the ignition is
switched on (or when the engine is cranking,
on X16 SZ engines) the pump is supplied with
voltage, by way of the pump relay and fuse
11, under the control of the Electronic Control
Unit (ECU). The pump feeds through the fuel
filter to the injector. Fuel pressure is controlled
by the pressure regulator, which lifts to allow
excess fuel to return to the tank.
4The air metering system includes the inlet air
temperature control system and the air
cleaner, but its main components are in the
throttle body assembly. This incorporates the
injector, which sprays fuel onto the back of the
throttle valve, the throttle potentiometer. This
is linked to the throttle valve spindle and sends
the ECU information on the rate of throttle
opening by transmitting a varying voltage. The
idle air control stepper motor is controlled by
the ECU to maintain the idle speed.
5The electrical side of the fuel injection
system consists of the ECU and all the
sensors that provide it with information, plus
the actuators by which it controls the whole
system’s operation. The basic method of
operation is as follows; note that the ignition
system is controlled by the same ECU.
6The manifold absolute pressure sensor is
connected by a hose to the inlet manifold.
Variations in manifold pressure are converted
into graduated electrical signals that are usedby the ECU to determine the load on the
engine. The throttle valve potentiometer is
explained above.
7Information on engine speed and
crankshaft position comes from the distributor
on C16 NZ engines and from the crankshaft
speed/position sensor on C16 NZ2, X16 SZ
and C18 NZ engines.
8An odometer frequency sensor provides the
ECU with information on the vehicle’s road
speed, and the coolant temperature sensor
provides it with the engine temperature. A
knock sensor located in the cylinder block
between cylinders 2 and 3 on the X16 SZ
engine provides additional information to the
ECU by detecting pre-ignition (detonation)
during the combustion process.
9All these signals are compared by the ECU
with set values pre-programmed (mapped)
into its memory. Considering this information,
the ECU selects the response appropriate to
those values. It controls the ignition amplifier
module by varying the ignition timing as
required. The fuel injector is controlled by
varying its pulse width the time the injector is
held open, to provide a richer or weaker
mixture, as appropriate. The idle air control
stepper motor controls the idle speed. The
fuel pump relay controls the fuel delivery and
the oxygen sensor, accordingly. The mixture,
idle speed and ignition timing are constantly
varied by the ECU to provide the best settings
for cranking, starting and engine warm-up
(with either a hot or cold engine), idling,
4B•2Fuel and exhaust systems - fuel injection models

4B
cruising and accelerating. The injector earth is
also switched off on the overrun to improve
fuel economy and reduce exhaust emissions.
Additionally, on the X16 SZ engine, the ECU
also controls the operation of the charcoal
canister purge valve in the evaporative
emission control system.
10The oxygen sensor screwed into the
exhaust manifold provides the ECU with a
constant feedback signal. This enables it to
adjust the mixture (closed-loop control) to
provide the best possible conditions for the
catalytic converter to operate effectively.
11Until the oxygen sensor is fully warmed up
it gives no feedback so the ECU uses
pre-programmed values (open-loop control) to
determine the correct injector pulse width.
When the sensor reaches its normal operating
temperature, its tip (which is sensitive to
oxygen) sends the ECU a varying voltage
depending on the amount of oxygen in the
exhaust gases. If the inlet air/fuel mixture is too
rich, the exhaust gases are low in oxygen so the
sensor sends a low-voltage signal. The voltage
rises as the mixture weakens and the amount of
oxygen rises in the exhaust gases. Peak
conversion efficiency of all major pollutants
occurs if the inlet air/fuel mixture is maintained
at the chemically correct ratio for the complete
combustion of petrol of 14.7 parts (by weight) of
air to 1 part of fuel (the “stoichiometric” ratio).
The sensor output voltage alters in a large step
at this point, the ECU using the signal change
as a reference point and correcting the inlet
air/fuel mixture accordingly by altering the fuel
injector pulse width.
12In addition, the ECU senses battery
voltage, incorporates diagnostic capabilities,
and can both receive and transmit information
by way of the diagnostic connector, thus
permitting engine diagnosis and tuning by
Vauxhall’s TECH1, test equipment.
Motronic system
13The Motronic type is available in several
different versions, depending on model. The
system is under the overall control of the
Motronic engine management system (Chapter
5), which also controls the ignition timing.
14Fuel is supplied from the rear-mounted
fuel tank by an electric fuel pump mounted
under the rear of the vehicle, through a
pressure regulator, to the fuel rail. The fuel rail
acts as a reservoir for the four fuel injectors,
which inject fuel into the cylinder inlet tracts,
upstream of the inlet valves. On SOHC
engines, the fuel injectors receive an electrical
pulse once per crankshaft revolution, which
operates all four injectors simultaneously. On
DOHC engines, sequential fuel injection is
used, whereby each injector receives an
individual electrical pulse allowing the four
injectors to operate independently, which
enables finer control of the fuel supply to each
cylinder. The duration of the electrical pulse
determines the quantity of fuel-injected, and
pulse duration is computed by the Motronic
module, based on the information received
from the various sensors.15On SOHC engines, inlet air passes from
the air cleaner through a vane type airflow
meter, before passing to the cylinder inlet
tracts through the throttle valve. A flap in the
vane airflow meter is deflected in proportion
to the airflow; this deflection is converted into
an electrical signal, and passed to the
Motronic module. A potentiometer screw
located on the airflow meter provides the
means of idle mixture adjustment, by altering
the reference voltage supplied to the Motronic
module.
16On DOHC engines, inlet air passes from
the air cleaner through a hot wire type air
mass meter, before passing to the cylinder
inlet tracts through a two-stage throttle body
assembly. The electrical current required to
maintain the temperature of the hot wire in the
air mass meter is directly proportional to the
mass flow rate of the air trying to cool it. The
current is converted into a signal, which is
passed to the Motronic module. The throttle
body contains two throttle valves that open
progressively, allowing high torque at part
throttle, and full-throttle, high-speed
“breathing” capacity. A potentiometer screw
located on the air mass meter provides the
means of idle mixture adjustment, by altering
the reference voltage supplied to the Motronic
module.
17A throttle position sensor enables the
Motronic module to compute the throttle
position, and on certain models, its rate of
change. Extra fuel can thus be provided for
acceleration when the throttle is opened
suddenly. Information from the throttle
position sensor is also used to cut off the fuel
supply on the overrun, thus improving fuel
economy and reducing exhaust gas
emissions.
18Idle speed is controlled by a variable-
orifice solenoid valve, which regulates the
amount of air bypassing the throttle valve. The
valve is controlled by the Motronic module;
there is no provision for direct adjustment of
the idle speed.
19Additional sensors inform the Motronic
module of engine coolant temperature, air
temperature, and on models fitted with a
catalytic converter, exhaust gas oxygen
content.
20A fuel filter is incorporated in the fuel
supply line, to ensure that the fuel supplied to
the injectors is clean.
21A fuel pump cut-off relay is controlled by
the Motronic module, which cuts the power to
the fuel pump should the engine stop with the
ignition switched on, if there is an accident. All
1993-onwards models equipped with
Motronic systems, have their fuel pump
located inside the fuel tank.
22The later M2.8 system is basically the
same as the earlier M2.5 system apart from
the following:
a)Hot Film Mass Airflow Meter - The hot
wire type unit used previously is replaced
on the M2.8 system by a hot film mass
airflow meter. The operation is the sameexcept that a thin, electrically heated plate
rather than a wire is used. The plate is
maintained at a constant temperature by
electric current as the inlet air mass
passing over the plate tries to cool it. The
current required to maintain the
temperature of the plate is directly
proportional to the mass flow rate of the
inlet air. The current is converted to a
signal that is passed to the Motronic
module.
b)Inlet Air Temperature Sensor -The sensor
is located in the hose between the hot
film mass airflow meter and the air cleaner
for precise monitoring of inlet air
temperature. Signals from the sensor are
used in conjunction with other sensors to
indicate the occurrence of a hot start
condition. The Motronic module then
interprets these signals to alter injector
duration accordingly.
c)Throttle Valve Potentiometer -On the
M2.8 system a throttle valve
potentiometer replaces the throttle valve
switch used previously.
Simtec system
23An increased amount of electronic
components are used instead of mechanical
parts as sensors and actuators with the
Simtec engine management system. This
provides more precise operating data as well
as greater problem free motoring.
24The control unit is equipped with
electronic ignition control. Called ‘Micropro-
cessor Spark Timing System, inductive
triggered’, (or MSTS-i), and means that the
mechanical high voltage distributor is no
longer needed. It is located behind the trim
panel, on the right-hand side footwell (door
pillar).
25The ignition coil is replaced by a dual
spark ignition coil, which is switched directly
by the output stages in the control unit.
26A camshaft sensor will maintain
emergency operation, should the crankshaft
inductive pulse pick-up, malfunction. These
sense TDC (‘Top Dead Centre’), crankshaft
angle and engine speed. The signals are used
by the control unit to calculate ignition point
and for fuel injection.
27The ‘hot film airflow meter’ determines the
mass of air taken in by the engine. The system
uses this information to calculate the correct
amount of fuel needed for injection in the
engine.
28The air inlet temperature sensor (NTC), is
fitted in the air inlet duct between the air
cleaner and the hot mass air flow meter.
29A controlled canister purge valve is
actuated by the system. The tank ventilation is
monitored closely with the Lambda control (or
oxygen sensor) and adaptation by the
computer within the control unit.
30A knock control system is also fitted. This
eliminates the need for octane number
adjustment, as it is performed automatically
through the control unit.
Fuel and exhaust systems - fuel injection models 4B•3

31This engine is also fitted with an EGR
(exhaust gas recirculation) valve and
secondary air injection (AIR - Air Injection
Reactor), to conform to the latest European
exhaust emission limits (as from 1996). The
EGR returns a specific amount of exhaust gas
into the combustion process. This in turn
reduces the formation of nitrogen oxides
(No
x). The secondary air injection system has
an electrically driven air pump that injects air
into the exhaust manifold, reducing the
amount of CO and HC emissions.
2Fuel injection system -
precautions
The fuel injection system is pressurised,
therefore extra care must be taken when
disconnecting fuel lines. When disconnecting
a fuel line union, loosen the union slowly, to
avoid a sudden release of pressure that may
cause fuel to spray out.
Fuel pressure checking must be entrusted
to a Vauxhall dealer, or other specialist, who
has the necessary special equipment.
3System testing - general
3
General
1Apart from basic electrical tests, there is
nothing that can be done by the owner to test
individual fuel system components.2If a fault arises, check first that it is not due
to poor maintenance. Check that the air
cleaner filter element is clean, the spark plugs
are in good condition and correctly gapped.
Check also that the engine breather hoses are
clear and undamaged and that the throttle
cable is correctly adjusted. If the engine is
running very roughly, check the compression
pressures (Chapter 1) and remember the
possibility that one of the hydraulic tappets
might be faulty, producing an incorrect valve
clearance.
3If the fault is thought to be due to a dirty
injector, it is worth trying one of the
established injector-cleaning treatments
before renewing, perhaps unnecessarily, the
injector.
4If the fault persists, check the ignition
system components (as far as possible).
5If the fault is still not eliminated, work
methodically through the system, checking all
fuses, wiring connectors and wiring, looking
for any signs of poor connections, dampness,
corrosion, dirt or other faults.
6Once the system components have been
checked for signs of obvious faults, take the
vehicle to a Vauxhall dealer for the full system
to be tested on special equipment.
7Do not attempt to “test” any component,
but particularly the ECU, with anything other
than the correct test equipment, available at a
Vauxhall dealer. If any of the wires to be
checked lead to a component such as the
ECU, always first unplug the relevant
connector from the system components so
that there is no risk of the component being
damaged by the application of incorrect
voltages from test equipment.
4Air cleaner - removal and
refitting
2
Note:If ‘round type’ air filter is fitted, follow
procedure in Chapter 4A.
Removal
1Unclip the coolant expansion tank hose
from the air cleaner cover, and move it to one
side out of the way.2Loosen the clamp screw and disconnect
the air trunking from the airflow meter (see
illustration).
3Disconnect the battery negative lead, then
disconnect the wiring plug from the airflow
meter.
4Release the two securing clips from the left-
hand side of the air cleaner cover, and
unscrew the two captive securing screws
from the right-hand side, then lift off the
cover.
5Lift out the filter element.
6Loosen the preheat hoses, fastening nuts.
7Undo the nuts securing the 2 rubber block
studs which are secured through the lower
half of the air cleaner housing.
8Some models are fitted with an inlet air
resonance box, to reduce induction noise.
This box is located under the wheel arch, and
connects to a pipe on the air inlet tube.
9The resonance box must be removed
before the air inlet tube can be removed. To
do this, first apply the handbrake, then jack up
the front of the vehicle, and support securely
on axle stands placed under the body side
members.
10Remove the securing screws, and
withdraw the lower splash shield from the
wing to expose the resonance box.
11Unscrew the single securing screw, and
pull the resonance box from the connector
tube (see illustrations).
12If desired, the air inlet tube can be
removed after pulling off the connector tube
from under the wing (see illustration).
4B•4Fuel and exhaust systems - fuel injection models
4.12 Removing the resonance box
connector tube4.11B . . . and withdraw the resonance box4.11A Remove the securing screw . . .
4.2 Loosening the air trunking clamp
screw at the airflow meter
Warning: Many of the
procedures in this sub-Section
require the removal of fuel lines
and connections that may result
in some fuel spillage. Before carrying out
any operation on the fuel system refer to
the precautions given in Safety first! at
the beginning of this Manual and follow
them implicitly. Petrol is a highly
dangerous and volatile liquid, and the
precautions necessary when handling it
cannot be overstressed.

regulator vacuum pipe should be routed over
the top of the camshaft cover breather hoses.
21On models with the Multec system note
also the following:
a)Fit the new diaphragm so that it locates in
the throttle body groove.
b)Ensure that the spring and spring seat are
correctly engaged with each other and
with the diaphragm and regulator cover.
Then press the cover over its locating
dowels and hold it in place while the
screws are tightened.
c)Tighten the screws carefully to the
specified torque wrench setting.
22On completion, check the regulator for
leaks, pressurising the system by switching
the ignition on and off several times, before
the engine is started.
22Idle speed adjuster - removal
and refitting
3
Note:Idle speed adjustment on models fitted
with Multec systems, is not possible, as it is
controlled by the ECU. Refer to Section 1.
Removal
SOHC models (except Multec system)
1Disconnect the battery negative lead.
2Disconnect the wiring plug from the idle
speed adjuster (see illustration).
3The adjuster can be removed complete with
its connecting hoses, or separately, leaving
the hoses in place.4Loosen the relevant clamp screws, then
disconnect the hoses, and withdraw the idle
speed adjuster (see illustration).
DOHC models
5Disconnect the battery negative lead.
6Loosen the clamp screw, and disconnect
the hose from underneath the air box on the
throttle body. Remove the clamp from the
hose.
7Apply the handbrake, then jack up the front
of the vehicle, and support securely on axle
stands (see “Jacking and Vehicle Support”)
placed under the body side members.
8Remove the engine undershield, as
described in Chapter 11.
9Working underneath the vehicle,
disconnect the wiring plug from the idle speed
adjuster, which is located underneath the inlet
manifold above the starter motor (see
illustration).
10Loosen the clamp screw and disconnect
the remaining idle speed adjuster hose from
the inlet manifold, then withdraw the adjuster
downwards complete with the hoses.
11If the hoses are to be removed from the
adjuster, mark their locations before removal
so that they can be correctly reconnected.
Once the adjuster has been refitted, it is
impossible to swap the hose positions.
Refitting
12Refitting is a reversal of removal. On
DOHC models ensure that the idle speed
adjuster rests horizontally, with the wiring
routed over the top of the coolant hose. If thewiring is routed under the coolant hose, this
may cause the idle speed adjuster to be bent
downwards, resulting in a restriction or
fracture in the air hose to the inlet manifold.
23Throttle position sensor -
removal and refitting
3
Removal
SOHC models
1Disconnect the battery negative lead.
2Disconnect the wiring plug from the throttle
position sensor (see illustration).
3Remove the two securing screws and
withdraw the sensor from the throttle body
(see illustration).
DOHC models
4Disconnect the battery negative lead.
5Disconnect the wiring plug from the air
mass meter. Recover the sealing ring.
6Loosen the clamp screw securing the air
trunking to the right-hand end of the air mass
meter.
7Using an Allen key or hexagon bit, unscrew
the four bolts securing the air box to the
throttle body. Lift the air box from the throttle
body, and disconnect the hose from the base
of the air box, then withdraw the air box/air
mass meter assembly.
8Disconnect the wiring plug from the throttle
position sensor wiring plug (see illustration).
Fuel and exhaust systems - fuel injection models 4B•11
22.9 Idle speed adjuster (arrowed) viewed
from underneath vehicle -
DOHC model
23.8 Disconnecting the throttle position
sensor wiring plug - DOHC model23.3 Removing a throttle position sensor
securing screw - SOHC early model23.2 Disconnecting the throttle position
sensor wiring plug - early SOHC models
22.4 Withdrawing the idle speed adjuster
complete with hoses - SOHC model
(except with Multec systems)22.2 Disconnecting the idle speed adjuster
wiring plug - SOHC models (except with
Multec systems)
4B

23Disconnect the wiring harness housing
from the fuel injectors, and move it to one
side, taking care not to strain the wiring. Pull
up on the wiring harness housing, and
compress the wiring plug retaining clips to
release the housing from the injectors.
24Unscrew and remove the two fuel rail
securing nuts, and withdraw the fuel rail
complete with fuel injectors from the inlet
manifold. Note the position of the earth leads
on the fuel rail securing studs (see
illustration).
25To remove an injector from the fuel rail,
prise out the metal securing clip using a
screwdriver, then pull the injector from the fuel
rail
Refitting
26Refitting is as described in paragraphs 8
to 11 inclusive.
29Fuel injector (Multec system)
- removal and refitting
3
Removal
1Depressurise the fuel system (see Sec
tion 8).
2Remove the air box (see Section 5).
3Disconnect the battery earth lead.
4Disconnect the wiring plug from the fuel
injector (see illustration).
5Undo the Torx-type screw (size TX 20)
securing the fuel injector retainer to the top ofthe throttle body, remove the retainer and lift
out the injector (see illustration). Remove
and discard the injector sealing rings.
Refitting
6Refitting is the reverse of the removal
procedure, noting the following points.
a)Always renew both sealing rings; apply a
smear of grease to each to ease injector
refitting (see illustration).
b)Refit the injector so that its wiring
terminals point to the rear of the vehicle;
locate the edge of the retainer securely in
the groove at the top of the injector.
c)Apply a few drops of a thread-locking
compound to the screw threads, then
tighten it carefully to the specified torque
wrench setting.
d)Switch on the ignition and check carefully
for signs of fuel leaks; if any signs of
leakage are detected, the problem must
be rectified before the engine is started.
30Fuel injector (Multec system)
- testing
3
1A simple test of the injector’s windings is
possible for those who have a multi-meter of
sufficient sensitivity. First disconnect the
injector wiring plug as described in Section 29,
then connect the meter (set to the appropriate
resistance scale) across the injector’s
terminals and note the reading obtained.
2On C18 NZ engines, the reading should be
within the specified tolerance; similar results
can be expected on C16NZ, C16NZ2, and
X16 SZ engines.
3If the reading differs significantly from the
specified value, indicating either shorted or
open circuit windings, the injector must be
renewed.
4Note that this is only a test of the injector’s
electrical condition; it does not test its spray
pattern or performance. If the injector is
thought to be faulty it is always worth trying a
well known injector-cleaning treatment. If this
fails, the vehicle must be taken to a Vauxhall
dealer for full testing on the special test
equipment.
31Throttle body (except Multec
system) - removal and refitting
3
Note:Refer to Section 2 before proceeding. A
new throttle body gasket must be used on
refitting
SOHC
Removal
1Disconnect the battery negative lead.
2Loosen the clamp screws securing the air
trunking to the throttle body and the airflow
meter, then withdraw the air trunking.
3Loosen the clamp screw, and disconnect
the idle speed adjuster hose from the throttle
body.
4Disconnect the camshaft cover breather
hose from the throttle body.
5Disconnect the coolant hoses from the
throttle body. Be prepared for coolant
spillage, and clamp or plug the open ends of
the hoses, to prevent further coolant loss.
6Disconnect the wiring plug from the throttle
position sensor.
7Release the securing clip, then disconnect
the throttle cable end balljoint from the throttle
valve lever.
8Slide the throttle cable grommet from the
bracket on the inlet manifold, then unhook the
throttle return spring from the bracket (see
illustration).
9Make a final check to ensure that all relevant
hoses and wires have been disconnected and
moved clear of the throttle body.
4B•14Fuel and exhaust systems - fuel injection models
28.24 Earth leads secured to fuel rail stud
(arrowed) - DOHC model29.5 Unscrewing the injector retainer Torx
screw
31.8 Unhook the throttle return spring
from the bracket on the inlet manifold
(inlet manifold removed for clarity)29.6 Renew injector sealing rings
(arrowed)
29.4 Disconnecting the fuel injector wiring
plug - Multec systems

4B
10Unscrew the four securing nuts, and
withdraw the throttle body from the inlet
manifold (see illustrations). Access to the
lower nuts is difficult and it may be necessary
to move the two fuel hoses to one side for
improved access. Take care not to strain the
hoses.
11Recover the gasket.
12If desired, the throttle position sensor can
be removed from the throttle body, with
reference to Section 23.
Refitting
13Refitting is a reversal of removal,
remembering the following points.
14Where applicable, refit the throttle
position sensor, as described in Section 23.
15Refit the throttle body, using a new gasket
(see illustration).
16Ensure that all hoses and wires are
correctly reconnected and routed.
17Check and if necessary top-up the
coolant level, as described in Chapter 3.
18Check and if necessary adjust the throttle
cable free play, as described in Section 19.
DOHC
Removal
19Disconnect the battery negative lead.
20Loosen the clamp screw securing the air
trunking to the left-hand side of the air mass
meter.
21Using an Allen key or hexagon bit,
unscrew the four bolts securing the air box tothe throttle body. Lift the air box from the
throttle body, and disconnect the hose from
the base of the air box, then withdraw the air
box.
22Disconnect the wiring plug from the
throttle position sensor.
23Unscrew the retaining nut, and remove
the fuel hose bracket from the left-hand side
of the throttle body (see illustration).
24Slide the throttle cable end from the
throttle valve lever.
25Disconnect the breather hose from the
front of the throttle body.
26Disconnect the vacuum pipe from the top
of the fuel pressure regulator.
27Make a final check to ensure that all
relevant hoses, pipes and wires have been
disconnected and moved clear of the throttle
body.
28Unscrew the four securing nuts, and
withdraw the throttle body from the inlet
manifold. Recover the gasket.
29If desired, the throttle position sensor can
be removed from the throttle body, referring
to Section 31, if necessary.
30Do not under any circumstances attempt
to adjust the throttle valve linkage. If the
throttle valve linkage is faulty, refer the
problem to a Vauxhall dealer.Refitting
31Refitting is a reversal of removal,
remembering the following points.
32Where applicable, refit the throttle
position sensor, as described in Section 23. 33Refit the throttle body, using a new
gasket.
34Ensure that all hoses, pipes and wires are
correctly reconnected and routed.
35On completion, check and if necessary
adjust the throttle cable free play, as
described in Section 19.
32Throttle body (Multec
system) - removal and refitting
3
Removal
1Depressurise the fuel system (Section 8).
2Remove the air box (see above).
3Disconnect the battery negative lead.
4Disconnect the wiring plugs from the fuel
injector (pressing out the wiring rubber
grommet), from the idle air control stepper
motor and from the potentiometer.
5Disconnect the fuel hoses from their unions
and plug them to prevent loss of fuel and the
entry of dirt; label them to ensure correct
refitting. Be prepared for fuel spillage and take
safety precautions.
6Disconnect the vacuum hoses and pipes
from the body unions.
7Disconnect the throttle valve operating
linkage at the throttle body.
8Undo the two nuts securing the throttle
body to the inlet manifold and withdraw the
body assembly; peel off and discard the
gasket (see illustration).
9If required, the throttle body’s upper and
lower sections may be separated by removing
the two Torx-type securing screws; note that
a new gasket must be fitted on reassembly.
The fuel inlet and return unions may also be
unscrewed, but note that new sealing rings
must be fitted on reassembly, and the unions
must be tightened securely.
Refitting
10Refitting is the reverse of the removal
procedure, noting the following points (see
illustration).
a)Renew all gaskets and seals, and use
thread-locking compound where
applicable.
Fuel and exhaust systems - fuel injection models 4B•15
31.15 Refit the throttle body, using a new
gasket32.8 Throttle body - Multec systems
A Mounting nuts
B Upper-to-lower section Torx screws31.23 Remove the fuel hose bracket
(arrowed) from the throttle body -
DOHC models
31.10B. . . and withdraw the throttle body
(inlet manifold removed for clarity) -
SOHC models31.10A Unscrew the securing nuts . . .

Refitting
5Refitting is a reversal of the removal
procedure, ensuring that the wiring plugs are
correctly reconnected and that the unit is
located securely.
36Knock sensor and module
(X16 SZ models) - removal
and refitting
3
Removal
1The knock sensor fitted to the X16 SZ
engine is located on the cylinder block below
the inlet manifold, between cylinders 2 and 3.
2Disconnect the battery negative lead.
3Remove the wiring and unscrew the unit
from the block.
4The module and control unit are located on
the left-hand side of the engine compartment
behind the battery. To remove, disconnect the
wiring multiplug and remove the retaining
bolts (see illustration).
5There is no provision for testing the knock
sensor or module without dedicated Vauxhall
test equipment. Check for external damage
and replace if necessary.
Refitting
6Refitting is a reversal of the removal
procedure, ensuring that the wiring plugs are
correctly reconnected and that the units are
located securely.
37Knock sensor (Simtec
system) - removal and refitting
3
Removal
1Disconnect the battery negative lead.
2Disconnect wiring harness plug, from inlet
air temperature sensor and wiring harness
plug, from hot mass air flow meter.
3Remove crankcase ventilation hoses.
4Remove coolant hoses from air inlet hoses,
hot film mass air flow meter complete with air
inlet hoses, from upper part of air cleaner and
throttle body.5Press retaining clip for 1st and 4th cylinder
injectors in plug strip (with screwdriver)
towards fuel distributor pipe - lifting plug strip
at the same time. On the underside of the plug
strip there are a total of 6 plug connections, 4
of which are for the injectors.
6Disconnect wiring harness plug for knock
sensor from the plug strip.
7Connect a 1 metre length of separate cable
to knock sensor wiring harness plug (note
routing).
8Remove knock sensor from cylinder block
(see illustration).
9Disconnect knock sensor cable from
separately attached cable, separate cable
remains in engine compartment.
Refitting
10Refitting is a reversal of removal, but note
the following.
11Before refitting ensure that the sensor is
spotlessly clean. Clean the entire contact
surface of the sensor must lie directly on the
cylinder block. Do not use any form of
washers.
12Carefully refit sensor into the block.
Tighten to the correct torque.
13Guide knock sensor cable between ridges
on inlet manifold using separate cable -
ensure correct routing.
14Remove the cable.
15Insert the wiring harness plug for the
knock sensor, into the plug strip.
16Correctly align the spring clips for theinjectors as they may prevent engagement of
the plug strip. Correct contact between the
plug strip and the injector is essential.
17When connecting plug strip, an audible
‘click’ should be heard.
18Ensure that hoses are in good condition
and installed securely with the two clamps.
38Inlet manifold (SOHC without
Multec) - removal and refitting
3
Note:Refer to warning in Section 2, before
proceeding. Use a new gaskets when refitting.
Removal
1Disconnect the battery negative lead.
2Remove the idle speed adjuster and its
hoses, referring to Section 22, if necessary.
3Release the securing clip, then disconnect
the throttle cable and balljoint from the throttle
valve lever. Slide the throttle cable grommet
from the bracket on the inlet manifold, and
move the throttle cable to one side out of the
way.
4Loosen the clamp screw and disconnect
the air trunking from the throttle body.
5Unscrew the union nut and disconnect the
brake servo vacuum hose from the inlet
manifold(see illustration).
6Disconnect the camshaft cover breather
hose from the throttle body.
7Disconnect the coolant hoses from the
throttle body. Be prepared for coolant
spillage, and clamp or plug the open ends of
the hoses, to prevent further coolant loss.
8Disconnect the wiring plug from the throttle
position sensor.
9Disconnect the vacuum pipe from the top
of the fuel pressure regulator.
10Disconnect the wiring harness housing
from the fuel injectors and move it to one side,
taking care not to strain the wiring. Pull up on
the wiring harness housing, and compress the
wiring plug retaining clips to release the
harness housing from the injectors.
11Disconnect the fuel hoses from the fuel
rail. Be prepared for fuel spillage, and take
adequate fire precautions. Clamp or plug the
open ends of the hoses, to prevent dirt
ingress and further fuel leakage.
Fuel and exhaust systems - fuel injection models 4B•17
38.5 Disconnecting the brake servo
vacuum hose -
SOHC models37.8 Knock sensor and wiring
(Simtec system)
1 Sensor2 Securing bolt
36.4 Knock sensor and module (X16 SZ models)
1 Sensor2 Module3 Sensor securing bolt
4B

12Unscrew and remove the top alternator
mounting nut and bolt.
13Make a final check to ensure that all
relevant hoses, pipes and wires have been
disconnected.
14Unscrew the securing nuts, and withdraw
the manifold from the cylinder head. Recover
the gasket (see illustrations).
15It is possible that some of the manifold
studs may be unscrewed from the cylinder
head when the manifold securing nuts are
unscrewed. In this event, the studs should be
screwed back into the cylinder head once the
manifold has been removed, using two
manifold nuts locked together.
16If desired, the ancillary components can
be removed from the manifold, referring to the
relevant Chapter.
Refitting
17Refitting is a reversal of removal,
remembering the following points.
18Where applicable refit any ancillary
components to the manifold, with reference to
relevant Sections of Chapters 4A or 4B.
19If the alternator mounting bracket has
been unbolted from the manifold, refit it
before refitting the manifold, as access to the
securing bolt is extremely limited once the
manifold is in place.
20Refit the manifold using a new gasket,
and tighten the securing nuts to the specified
torque.
21Ensure that all relevant hoses, pipes and
wires are correctly reconnected.
22On completion, check and if necessary
top-up the coolant level, (Chapter 3).
23Check and if necessary adjust the throttle
cable free play, as described in Chapters 4A
or 4B, as applicable.
24If any of the fuel system components have
been disturbed or renewed, check and if
necessary adjust the idle mixture, as
described in Chapters 4A or 4B, as applicable.
39Inlet manifold (SOHCwith
Multec) - removal and refitting
3
Removal
1Depressurise the fuel system Section 8).
2Remove the air box (see Section 5).
3Disconnect the battery negative lead.
4Either remove the throttle body assembly
(see Section 32), or disconnect the throttle
cable, wiring, fuel and vacuum hoses and
pipes to allow the manifold to be removed
with the throttle body.
5Drain the cooling system (see Chapter 3).
6Continue as described in Chapter 4A,
Section 26, paragraph 4 onwards.
Refitting
7Refitting is the reverse of the removal
procedure; renew all gaskets and seals
disturbed.
40Inlet manifold (DOHC
models) - removal and
refitting
3
Removal
1Disconnect the battery negative lead.
2Disconnect the wiring plug from the air
mass meter. Recover the sealing ring.
3Loosen the clamp screw securing the air
trunking to the right-hand end of the air mass
meter.
4Using an Allen key or hexagon bit, unscrew
the four bolts securing the air box to the
throttle body. Lift the air box from the throttle
body, and disconnect the hose from the base
of the air box then withdraw the air box/air
mass meter assembly.
5Disconnect the wiring plug from the throttle
position sensor.
6Slide the throttle cable end from the throttle
valve lever. Then pull the cable end grommet
from the bracket on the inlet manifold and
move the throttle cable to one side out of the
way.
7Disconnect the two breather hoses from the
rear of the camshaft cover. Disconnect the
larger hose from the throttle body, and
remove the hose completely.
8Position a wad of rag beneath one of the
fuel hose unions on the fuel rail, to absorb the
fuel that will be released as the union is
disconnected.
9Slowly loosen the fuel hose union, to
gradually relieve the pressure in the fuel feed
line, then disconnect the hose from the fuel
rail. Be prepared for fuel spillage, and take
adequate fire precautions. Plug the end of the
fuel hose, to prevent dirt ingress and further
fuel leakage.
10Repeat paragraphs 9 and 10 for the
remaining fuel hose-to-fuel rail union.
11Disconnect the vacuum pipe from the top
of the fuel pressure regulator.
12Disconnect the wiring harness housing
from the fuel injectors and move it to one side,
taking care not to strain the wiring. Pull up on
the wiring harness housing, and compress the
wiring plug retaining clips to release the
housing from the injectors.
13Unscrew the union nut, and disconnectthe brake servo vacuum hose from the left-
hand side of the inlet manifold (see
illustration).
14Unscrew the retaining nut, and remove
the fuel hose bracket from the left-hand side
of the throttle body.
15Unscrew the securing nuts, and
disconnect the earth leads from the fuel rail
securing studs at either end of the fuel rail.
16Unscrew the securing bolt, and remove
the cable/hose bracket from the left-hand end
of the inlet manifold.
17Remove the idle speed adjuster, as
described in Section 22.
18Unscrew and remove the top alternator
mounting nut and bolt.
19Make a final check to ensure that all
relevant hoses, pipes and wires have been
disconnected.
20Unscrew the securing nuts, and withdraw
the manifold from the cylinder head. Recover
the gasket.
21It is possible that some of the manifold
studs may be unscrewed from the cylinder
head when the manifold securing nuts are
unscrewed. In this event, the studs should be
screwed back into the cylinder head once the
manifold has been removed, using two
manifold nuts locked together.
22If desired, the ancillary components can
be removed from the manifold, with reference
to the relevant Sections of Chapters 4A or 4B.
Refitting
23Refitting is a reversal of the removal
procedure.
4B•18Fuel and exhaust systems - fuel injection models
38.14A Unscrew the securing nuts
40.13 Brake servo vacuum hose
connection at inlet manifold (arrowed) -
DOHC models
38.14B ...and withdraw the inlet manifold -
SOHC models