1988 OPEL CALIBRA gas type

Aluminium or plastic mesh, or glass fibre
matting, is probably the best material to use
for a large hole. Cut a piece to the
approximate size and shape of the hole to be
filled, then position it in the hole so that its
edges are below the level of the surrounding
bodywork. It can be retained in position by
several blobs of filler paste around its
periphery.
Aluminium tape should be used for small or
very narrow holes. Pull a piece off the roll and
trim it to the approximate size and shape
required. Then pull off the backing paper (if
used) and stick the tape over the hole. It can
be overlapped if the thickness of one piece is
insufficient. Burnish down the edges of the
tape with the handle of a screwdriver or
similar, to ensure that the tape is securely
attached to the metal underneath.
Bodywork repairs filling and
re-spraying
Before using this Section, see the Sections
on dent, deep scratch, rust holes and gash
repairs.
Many types of bodyfiller are available, but
generally those proprietary kits that contain a
tin of filler paste and a tube of resin hardener
are best for this type of repair. These can be
used directly from the tube. A wide, flexible
plastic or nylon applicator will be found
invaluable for imparting a smooth and well-
contoured finish to the surface of the filler.
Mix up a little filler on a clean piece of card
or board - measure the hardener carefully
(follow the maker’s instructions on the pack)
otherwise the filler will set too rapidly or too
slowly. Using the applicator apply the filler
paste to the prepared area; draw the
applicator across the surface of the filler to
achieve the correct contour and to level the
filler surface. When a contour that
approximates to the correct one is achieved,
stop working the paste - if you carry on too
long the paste will become sticky and begin to
“pick up” on the applicator. Continue to add
thin layers of filler paste at twenty-minute
intervals until the level of the filler is just proud
of the surrounding bodywork.
Once the filler has hardened, excess can be
removed using a metal plane or file. From then
on, progressively finer grades of abrasive
paper should be used, starting with a 40
grade production paper and finishing with 400
grade wet-and-dry paper. Always wrap the
abrasive paper around a flat rubber, cork, or
wooden block otherwise the surface of the
filler will not be completely flat. During the
smoothing of the filler surface the wet-and-dry
paper should be periodically rinsed in water.
This will ensure that a very smooth finish is
imparted to the filler at the final stage.
At this stage the “dent” should be
surrounded by a ring of bare metal, which in
turn should be encircled by the finely
“feathered” edge of the good paintwork.
Rinse the repair area with clean water, until all
the dust produced by the rubbing-down
operation has gone.Spray the whole repair area with a light coat
of primer. This will show up any imperfections
in the surface of the filler. Repair these
imperfections with fresh filler paste or
bodystopper, and again smooth the surface
with abrasive paper. If bodystopper is used, it
can be mixed with cellulose thinners to form a
thin paste that is ideal for filling small holes.
Repeat this spray and repair procedure until
you are satisfied that the surface of the filler,
and the feathered edge of the paintwork are
perfect. Clean the repair area with clean water
and allow to dry fully.
The repair area is now ready for final
spraying. Paint spraying must be carried out
in a warm, dry, windless and dust free
atmosphere. This condition can be created
artificially if you have access to a large indoor
working area, but if you are forced to work in
the open, you will have to pick your day very
carefully. If you are working indoors, dousing
the floor in the work area with water will help
to settle the dust that would otherwise be in
the atmosphere. If the repair area is confined
to one body panel, mask off the surrounding
panels; this will help to minimise the effects of
a slight miss-match in paint colours.
Bodywork fittings (e.g. chrome strips, door
handles, etc.), will also need to be masked off.
Use genuine masking tape and several
thicknesses of newspaper for the masking
operations.
Before beginning to spray, agitate the
aerosol can thoroughly, then spray a test area
(an old tin, or similar) until the technique is
mastered. Cover the repair area with a thick
coat of primer; the thickness should be built
up using several thin layers of paint rather
than one thick one. Using 400 grade
wet-and-dry paper, rub down the surface of
the primer until it is smooth. While doing this,
the work area should be thoroughly doused
with water, and the wet-and-dry paper
periodically rinsed in water. Allow to dry
before spraying on more paint.
Spray on the top coat, again building up the
thickness by using several thin layers of paint.
Start spraying in the centre of the repair area
and then work outwards, with a side-to-side
motion, until the whole repair area and about
2 inches of the surrounding original paintwork
is covered. Remove all masking material 10 to
15 minutes after spraying on the final coat of
paint.
Allow the new paint at least two weeks to
harden, then using a paintwork renovator or a
very fine cutting paste, blend the edges of the
paint into the existing paintwork. Finally, apply
wax polish.
Plastic components
With the use of more and more plastic body
components (e.g. bumpers, spoilers, and in
some cases major body panels), repair of
more serious damage to such items has
become a matter of either entrusting repair
work to a specialist in this field, or renewing
complete components. Repair of suchdamage by the DIY owner is not feasible
owing to the cost of the equipment and
materials required for effecting such repairs.
The basic technique involves making a groove
along the line of the crack in the plastic using
a rotary burr in a power drill. The damaged
part is then welded back together by using a
hot air gun to heat up and fuse a plastic filler
rod into the groove. Any excess plastic is then
removed and the area rubbed down to a
smooth finish. It is important that a filler rod of
the correct plastic is used, as body
components can be made of a variety of
different types (e.g. polycarbonate, ABS,
polypropylene).
Damage of a less serious nature (abrasions,
minor cracks, etc.), can be repaired by the DIY
owner using a two-part epoxy filler repair
material. Once mixed in equal proportions this
is used in similar fashion to the bodywork filler
used on metal panels. The filler is usually
cured in twenty to thirty minutes, ready for
sanding and painting.
If the owner is renewing a complete
component himself, or if he has repaired it
with epoxy filler, he will have a problem of
finding a paint for finishing which is
compatible with the type of plastic used. At
one time the use of a universal paint was not
possible owing to the complex range of
plastics come across in body component
applications. Standard paints, generally, will
not bond to plastic or rubber satisfactorily, but
special paints are available to match any
plastic or rubber finish can be obtained from
dealers. However, it is now possible to obtain
a plastic body parts finishing kit that consists
of a pre-primer treatment, a primer and
coloured top coat. Full instructions are
normally supplied with a kit, but the method of
use is to first apply the pre-primer to the
component concerned and allow it to dry for
up to 30 minutes. Then the primer is applied
and left to dry for about an hour before finally
applying the special coloured top coat. The
result is a correctly coloured component
where the paint will flex with the plastic or
rubber, a property that standard paint does
not normally possess.
5Major body damage - repair
5
Major impact or rust damage should only
be repaired by a Vauxhall dealer or other
competent specialist. Alignment jigs are
needed for successful completion of such
work, superficially effective repairs may leave
dangerous weaknesses in the structure.
Distorted components can also impose
severe stresses on steering and suspension
components with consequent premature
failure.
Bodywork and fittings 11•3
11

4The cut-off valve can now be removed from
the bracket.
Testing
5To test the cut-off valve a vacuum hand
pump with gauge will be required. If available,
connect to the cut-off valve and ensure that
air through-flow aperture is fully open.
Refitting
6Refitting is a reversal of removal. Ensure
valve is fitted in the correct direction.
8AIR switchover valve -
removal and refitting
3
Removal
1Disconnect the battery negative lead.
2Disconnect wiring plug from the valve.
3Mark the location of the vacuum hoses
before removing them from the valve.
4After disconnecting the hoses undo the two
bolts, and remove them from its bracket.
Refitting
5Refitting is a reversal of removal. Ensure
hoses are fitted correctly (see illustration).
9AIR pipe and non-return
valve - removal and refitting
3
Note:New air pipe washers will be required
when refitting.
Removal
1Remove the non-return valve air duct hose.
2Undo the bolts engine lifting eye bracket,
and turn the bracket on to its left hand side.
3Remove the pipe support bracket by
releasing its three bolts.
4Remove the heat shield that is secured by
two bolts.
5The air pipe can now be removed by
releasing the two securing bolts.
6If necessary the non-return valve can now
be disconnected.
7Carefully clamp the pipe using a vice with
protective jaws. Unbolt the valve from the
pipe, clean and inspect for damage.
Refitting
8Before refitting, coat the threads of the non-
return valve with sealing compound (i.e.
Vauxhall part no. 90094714).
9Use new washers when refitting the pipe,
(take care as the washers have sharp edges).
Coat the pipe mounting bolts with assembly
paste (i.e. Vauxhall part no. 90513210), before
refitting.
10Refitting is a reversal of removal.
Retighten to correct torque as shown in Spec-
ifications.
10Catalytic converter -
description, general and
precautions
Note: The catalytic converter is not a filter. It
creates a chemical reaction, but it is not
affected by that reaction.
Description
1Certain models are available with a catalytic
converter, to reduce exhaust emissions.
These models can be identified by a ‘C’ or ‘X’,
prefixing the engine code.
2The purpose of the catalytic converter is to
change potentially harmful hydrocarbon andcarbon monoxide exhaust gases into harmless
gases and water vapour. The converter
consists of a stainless steel canister containing
a catalyst-coated honeycomb ceramic. The
catalyst is a mixture of three precious metals,
platinum, palladium and rhodium.
3The exhaust gases pass freely through the
honeycomb, where the catalyst speeds up the
chemical change of the exhaust gases,
without being permanently altered itself.
4To avoid damage to the catalyst, the engine
must be kept properly tuned, and unleaded
petrol must always be used. Normal leaded
petrol will “poison” the catalyst, and must not
be used.
5To enable the Motronic engine management
system to achieve complete combustion of the
fuel mixture, and thus to minimise exhaust
emissions, an oxygen sensor is fitted in the
exhaust gas stream. The sensor monitors the
oxygen level in the exhaust gas, and sends a
signal to the Motronic module. The module
constantly alters the fuel/air mixture within a
narrow band to reduce emissions, and to allow
the catalytic converter to operate at maximum
efficiency. No adjustment of idle mixture is
therefore possible on models fitted with a
catalytic converter.
General
6Ninety-nine per cent of exhaust gases, from
a petrol engine (however efficient or well
tuned), consists of nitrogen (N
2), carbon
dioxide (CO
2), oxygen (O2), other inert gases
and water vapour (H
2O). The remaining 1% is
made up of the noxious materials that are
currently seen (except CO
2), as the major
polluters of the environment. Carbon
monoxide (CO), unburned hydrocarbons (HC),
oxides of nitrogen (NOx) and some solid
matter, including a small lead content.
7The device most commonly used to clean
up vehicle exhausts is the catalytic converter.
It is fitted into the vehicle’s exhaust system
and uses precious metals (platinum and
palladium or rhodium) as catalysts to speed
up the reaction between the pollutants and
the oxygen in the exhaust gases. CO and HC
being oxidised to form H
2O and CO2and (in
the three-way type of catalytic converter) NOx
being reduced to N
2.
8The converter consists of an element of
ceramic honeycomb, coated with a
combination of precious metals in such a way
as to produce a vast surface area over which
the exhaust gases must flow. The three-way
closed-loop type converter fitted to these
models can remove over 90% of pollutants.
9The catalytic converter is a reliable and
simple device that needs no maintenance.
However there are some facts that an owner
should be aware if the converter is to function
properly for its full service life (see
illustration).
a)DO NOT use leaded petrol in a vehicle
equipped with a catalytic converter. The
lead will coat the precious metals,
reducing their converting efficiency and
will eventually destroy the converter.
Fuel and exhaust systems - exhaust and emissions 4C•3
10.9 The catalytic converter is protected
by heat shields
8.5 AIR switchover valve
1 Connection to brake servo vacuum hose
2 Connection to cut-off valve
7.1 AIR cut-off valve
1 Connection to AIR pump
2 Connection to AIR switchover valve
3 Connection to AIR non-return valve
4C

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.

4Where applicable, the only test of the
catalytic converter’s efficiency is to check the
level of CO in the exhaust gas. This is
measured at the tailpipe with the engine
running (with no load) at 3000 rpm. If the CO
level exceeds the specified value, the Vauxhall
test equipment must be used to check the
entire fuel injection/ignition system. If the
engine is mechanically sound, once the
system has been eliminated, the fault must lie
in the converter, which must be renewed.
Motronic systems
Checking
5In order to check the idle mixture adjustment,
the following conditions must be met:
a)The engine must be at normal operating
temperature
b)All electrical consumers (cooling fan,
heater blower, headlamps etc.) must be
switched off
c)The spark plug gaps must be correctly
adjusted see Chapter 1
d)The throttle cable free play must be
correctly adjusted - see Section 19
e)The air inlet trunking must be free from
leaks, and the air filter must be clean
Adjustment
6Connect a tachometer and an exhaust gas
analyser to the vehicle in accordance with the
equipment manufacturer’s instructions.
7Start the engine and turn it at 2000 rpm for
approximately 30 seconds, then allow it to
idle. Check that the idle speed is within the
specified limits. No adjustment of idle speed
is possible, and if outside the specified limits,
the problem should be referred to a dealer.
8With the idle speed correct, check the CO
level in the exhaust gas. If it is outside the
specified limits, adjust by means of the idle
mixture adjustment screw in the airflow meter
or air mass meter, as applicable. In
production, the screw is covered by a
tamperproof plug; ensure that no local or
national laws are being broken before
removing the plug.9If the cooling fan cuts in during the
adjustment procedure, stop the adjustments,
and proceed when the cooling fan stops.
10When the idle mixture is correctly set,
stop the engine and disconnect the test
equipment.
Simtec systems
11Adjustment is not possible on these
models.
21Fuel pressure regulator -
removal and refitting
3
Note:Refer to Section 2 before proceeding
Removal
SOHC models (except Multec systems)
1Disconnect the battery negative lead.
2For improved access, remove the idle
speed adjuster as described in Section 22.
Disconnect 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.
3Position a wad of rag beneath the pressure
regulator, to absorb the fuel that will be
released as the regulator is removed.
4Loosen the clamp screws and disconnect
the fuel hoses from the regulator. Be prepared
for fuel spillage, and take adequate fire
precautions.
5Disconnect the vacuum pipe from the top
of the pressure regulator and withdraw the
regulator.
SOHC models (with Multec system)
6Depressurise the fuel system, as described
in Section 8.
7Remove the air box. Refer to Section 5, if
necessary.
8Disconnect the battery earth lead.9Noting the dowels locating the cover,
carefully unscrew the fuel pressure regulator
cover Torx-type screws (size TX 15). Ensure
that the spring does not fly out as the cover is
released. Remove the cover spring seat,
spring and diaphragm, noting how each is
fitted (see illustration).
10The diaphragm must be renewed
whenever the cover is disturbed. If any of the
regulator’s other components are worn or
damaged, they can be renewed only as part
of the throttle body upper section assembly.
DOHC models
11Disconnect the battery negative lead.
12Disconnect the wiring plug from the air
mass meter. Recover the sealing ring.
13Loosen the clamp screw securing the air
trunking to the right-hand end of the air mass
meter.
14Using 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.
15Disconnect the two breather hoses from
the rear of the camshaft cover, and move
them to one side.
16Disconnect the wiring plug from the
throttle position sensor.
17Disconnect the vacuum pipe from the top
of the pressure regulator (see illustration).
18Position a wad of rag beneath the
regulator, to absorb the fuel that will be
released as the regulator is removed.
19Using a spanner or socket, and working
underneath the regulator, unscrew the four
Torx type securing bolts, then withdraw the
regulator. Be prepared for fuel spillage, and
take adequate fire precautions.
Refitting
20Refitting is a reversal of removal, ensuring
that all wires, pipes and hoses are correctly
reconnected. Note that on DOHC models, the
4B•10Fuel and exhaust systems - fuel injection models
21.17 Fuel pressure regulator (arrowed) - DOHC model21.9 Fuel pressure regulator cover
A Locating dowels B Mounting screws

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 . . .

b)Check the throttle cable operation and
adjustment (see above).
c)When reconnecting the vacuum hoses
and pipes, ensure that they are connected
to the front unions as shown in the
accompanying photograph.
d)As no fuel vapour trap is fitted, it is
essential that the manifold absolute
pressure sensor vacuum hose is routed
so that it falls steadily from the sensor to
the throttle body. This precaution will
prevent any fuel droplets being trapped in
the sensor or hose and allowing them to
drain into the inlet port.
e)Ensure that the fuel hoses are correctly
reconnected; the feed hose is on the
injector end of the throttle body.
f)Switch on the ignition and check for signs
of fuel leaks from all disturbed unions; if
any signs of leakage are detected, the
problem must be rectified before the
engine is started.
33Idle air control stepper
motor - removal and refitting
3
Removal
1Remove the air box (see Section 5).
2Disconnect the battery earth lead.3Disconnect the wiring plug from the stepper
motor (see illustration).
4Undo its two screws, then withdraw the
stepper motor. Remove and discard the
sealing ring (see illustrations).
Refitting
5Refitting is the reverse of the removal
procedure, noting the following points.
a)Fit a new sealing ring, greasing it lightly to
ease installation.
b)To prevent the risk of damage, either to
the throttle body or to the stepper motor,
if the motor’s plunger tip projects more
than 28 mm (1.1 in) beyond the motor’s
mating surface, carefully press the
plunger in until its stop is reached. The
stepper motor will then be reset by the
ECU when the engine is restarted.
c)Apply a few drops of a thread-locking
compound to their threads, then carefully
tighten the screws to the specified torque
wrench setting.
34Throttle potentiometer -
removal and refitting
3
Removal
1Disconnect the battery negative lead.
2Disconnect the wiring plug from the
potentiometer (see illustration).
3Unscrew the two Torx-type securing
screws (size TX 25) and withdraw the
potentiometer.
Refitting
4Refitting is the reverse of the removal
procedure, noting the following points.
a)Install the potentiometer when the throttle
valve is fully closed, and ensure that its
adapter seats correctly on the throttle
valve spindle.
b)Tighten the screws carefully to the
specified torque.
35Electronic Control Unit
(ECU) - removal and refitting
3
Removal
1Disconnect the battery negative lead.
2Remove the driver’s footwell side trim panel
(Chapter 11).
3Release the unit from its mountings and
withdraw it until the wiring plugs’ locking lugs
can be released and the plugs can be
disconnected (see illustration).
4Note that the unit consists of two parts the
basic control unit and the Programmable
Read Only Memory (PROM). While it is
possible to renew them separately, do not
attempt to separate them. Faults requiring this
degree of attention can be diagnosed only by
an experienced mechanic using the special
Vauxhall test equipment. A previously sound
ECU could be seriously damaged by careless
handling of the contacts between the two
sub-units.
4B•16Fuel and exhaust systems - fuel injection models
32.10 Intake air temperature control -
Multec systems
A Vacuum pipe
B Exhaust gas recirculation valve hose
C Charcoal canister control pipe
D Fuel return hose
33.4A Unscrew retaining screws (second
screw arrowed) . . .
35.3 Withdrawing the fuel
injection/ignition system ECU34.2 Disconnecting the throttle
potentiometer wiring plug - note the
mounting screws (arrowed)
33.4B . . . to remove the stepper motor -
renew sealing ring (arrowed)
33.3 Disconnecting the idle air control
stepper motor wiring plug