1988 OPEL CALIBRA relay

5If the ‘ABS’ symbol, in the instrument panel
stays lit after approximately 4 seconds, or if it
comes on sporadically or stays on whilst
driving, there is a fault in the system. Should
this occur, it is recommended that a complete
test is carried out by a Vauxhall dealer, who
will have the necessary specialist diagnostic
equipment. Due to the special equipment
required, it is not practical for the DIY
mechanic to carry out the test procedure.
6To prevent possible damage to the
electronic control unit, always disconnect the
control unit wiring plug before carrying out
electrical welding work.
7It is recommended that the control unit is
removed if the vehicle is being subjected to
high temperatures, like for instance, during
certain paint-drying processes.
8If using steam cleaning equipment, do not
aim the water/steam jet directly at the control
unit.
9Do not disconnect the control unit wiring
plug with the ignition switched on.
10Do not use a battery booster to start the
engine.
11After working on the ABS components,
ensure that all wiring plugs are correctly
reconnected, and have the complete system
tested by a Vauxhall dealer, at the earliest
opportunity.
12All models up to 1991 that were fitted with
ABS, used the ABS-2E system. From 1992
onwards an ABS-2EH system was fitted,
which can be identified by the location of the
electronic control module, which is bolted to
the hydraulic modulator.
13The main differences between the two
systems are in the electrical components and
circuits, the most obvious of these being
omission of the surge arrester relay on the
2EH system.
3Hydraulic system - bleeding
2
General
1If any of the hydraulic components in the
braking system have been removed or
disconnected, or if the fluid level in the
reservoir has been allowed to fall appreciably,
it is certain that air will have entered into the
system. The removal of all this air from the
hydraulic system is essential if the brakes are
to function correctly, and the process of
removing it is known as bleeding.
2Where an operation has only affected one
circuit of the hydraulic system (the system issplit diagonally on non-ABS models, and front
and rear on ABS models), then it will only be
necessary to bleed the relevant circuit. If the
master cylinder has been disconnected and
reconnected, or the fluid level has been
allowed to fall appreciably, then the complete
system must be bled.
3One of three methods can be used to bleed
the system, although Vauxhall recommend
the use of a pressure bleeding kit.
Bleeding - two-man method
4Obtain a clean jar, and a length of rubber or
plastic bleed tubing that will fit the bleed
screws tightly. The help of an assistant will be
required.
5Remove the dust cap and clean around the
bleed screw on the relevant caliper of wheel
cylinder (see illustration), then attach the
bleed tube to the screw. If the complete
system is being bled, start at the front of the
vehicle. When bleeding the complete system
on models with ABS, the front brakes must be
bled before the rears.
6Check that the fluid reservoir is topped up,
and then destroy the vacuum in the brake
servo by giving several applications of the
brake pedal.
7Immerse the open end of the bleed tube in
the jar, which should contain two or three
inches of hydraulic fluid. The jar should be
positioned about 300 mm (12.0 in) above the
bleed screw to prevent any possibility of air
entering the system down the threads of the
bleed screw when it is slackened.
8Open the bleed screw half a turn, and have
the assistant depress the brake pedal slowly
to the floor. With the brake pedal still
depressed, retighten the bleed screw, and
then have the assistant quickly release the
pedal. Repeat the procedure.
9Observe the submerged end of the tube in
the jar. When air bubbles cease to appear,
tighten the bleed screw when the pedal is
being held fully down by the assistant.
10Top-up the fluid reservoir. It must be kept
topped up throughout the bleeding
operations. If the connecting holes to the
master cylinder are exposed at any time due
to low fluid level, the air will be drawn into the
system, and the whole bleeding process will
have to start again.
11If the complete system is being bled, the
procedure should be repeated on the
diagonally opposite rear brake. Then on the
front and rear brakes of the other circuit on
non-ABS models, or on the remaining front
brake and then on the rear brakes on ABS
models.
12On completion, remove the bleed tube,
and discard the fluid that has been bled from
the system, unless it is required to make up
the level in the bleed jar. Never re-use old fluid.
13On completion of bleeding, top-up the
fluid level in the reservoir. Check the action ofthe brake pedal, which should be firm, and
free from any “sponginess” that would
indicate that air is still present in the system.
Bleeding - with one-way valve
14There are a number of one-man brake
bleeding kits currently available from motor
accessory shops. It is recommended that one
of these kits should be used whenever
possible, as they greatly simplify the bleeding
operations. They also reduce the risk of
expelled air or fluid being drawn back into the
system.
15Proceed as described in paragraphs 5
and 6.
16Open the bleed screw half a turn, then
depress the brake pedal to the floor, and
slowly release it. The one-way valve in the
bleeder device will prevent expelled air from
returning to the system at the completion of
each stroke. Repeat the operation until clear
hydraulic fluid, free from air bubbles, can be
seen coming through the tube. Tighten the
bleed screw.
17Proceed as described in paragraphs 11
to 13 inclusive.
Bleeding - with pressure
bleeding kit
18These are also available from motor
accessory shops, and are usually operated by
air pressure from the spare tyre.
19By connecting a pressurised container to
the master cylinder fluid reservoir, bleeding is
then carried out by simply opening each bleed
screw in turn and allowing the fluid to run out.
Like turning on a tap, until no air bubbles are
visible in the fluid being expelled.
20Using this method, the large reserve of
fluid provides a safeguard against air being
drawn into the master cylinder during the
bleeding operations.
21This method of bleeding is recommended
by Vauxhall.
22Begin bleeding with reference to
paragraphs 5 and 6, and continue as
described in paragraphs 11 to 13 inclusive.
Braking system 9•3
3.5 Removing the dust cap from a rear
caliper bleed screw - models with
ventilated discs
9
If brake fluid is spilt on the
paintwork, the affected area
must be washed down with
cold water immediately.
Brake fluid is an effective paint
stripper!

16If adjustment is necessary, slacken the
locknut, turn the fork to give the specified
dimension, then tighten the locknut.
17Where applicable, coat the contact faces
of the servo and the mounting bracket with
sealing compound, then refit the bracket to
the servo, and tighten the securing nuts to the
specified torque.
18Coat the threads of the servo securing
bolts with locking fluid, then fit the servo to
the bulkhead and tighten the securing bolts.
19Refit the securing bolt cover plugs to the
cowl panel.
20Refit the master cylinder to the servo, and
tighten the securing nuts to the specified
torque.
21Reconnect the vacuum pipe to the servo.
22Refit the coolant expansion tank, as
described in Chapter 3.
23Refit the windscreen wiper motor and
linkage as described in Chapter 12, then refit
the windscreen cowl panel.
24Further refitting is a reversal of removal.
On completion, test the operation of the
servo, as described in Section 18.
20ABS hydraulic modulator -
removal and refitting
4
Note: Refer to Section 2, and the note at the
beginning of Section 3, before proceeding
Removal
1Disconnect the battery negative lead.
2Remove the brake fluid reservoir cap, and
secure a piece of polythene over the filler
neck with a rubber band, or by refitting the
cap. This will reduce the loss of fluid during
the following procedure.
3Remove the securing screw, and withdraw
the plastic cover from the hydraulic
modulator.
4Remove the two clamp screws, and lift off
the modulator wiring harness clamp (see
illustration).
5Disconnect the modulator wiring plug,
levering it from the socket with a screwdriver if
necessary.6Unscrew the brake fluid pipe union nuts,
and disconnect the pipes from the modulator.
Be prepared for fluid spillage, and plug the
open ends to prevent dirt ingress and further
fluid loss. Move the pipes just clear of the
modulator, taking care not to strain them.
7Unscrew the three modulator securing nuts
(see illustration), then tilt the modulator
slightly, and withdraw it upwards from its
bracket, sufficiently to gain access to the
earth lead securing nut at the front lower edge
of the modulator.
8Unscrew the securing nut and disconnect
the earth lead, then withdraw the modulator
from the vehicle, taking care not to spill brake
fluid on the vehicle paintwork.
9If a new modulator is to be fitted, pull the
two relays from the top of the old modulator,
and transfer them to the new unit. No attempt
must be made to dismantle the modulator.
Refitting
10Before refitting the modulator, check that
the bolts securing the mounting bracket to the
body panel are tight, and that the modulator
rubber mountings are in good condition.
Renew the rubber mountings if necessary.
11Refitting is a reversal of removal,
remembering the following points.
12Make sure that the earth lead is
reconnected before fitting the modulator to its
mounting bracket.13On completion, remove the polythene
sheet from the brake fluid reservoir filler neck,
and bleed the complete brake hydraulic
system, as described in Section 3.
14Check that the ABS warning lamp
extinguishes when first starting the engine
after the modulator has been removed. At the
earliest opportunity, take the vehicle to a
Vauxhall dealer, and have the complete
system tested, using the dedicated ABS test
equipment.
21ABS wheel sensors - removal
and refitting
3
Note: Refer to Section 2 before proceeding
Front wheel sensor
Removal
1Disconnect the battery negative lead.
2Where applicable, remove the wheel trim,
then loosen the relevant front roadwheel bolts
and apply the handbrake. Jack up the front of
the vehicle, and support on axle stands (see
“Jacking and Vehicle Support”) positioned
under the body side members. Remove the
roadwheel.
3Unclip the sensor wiring connector from the
retaining clip under the wheel arch, then
separate the two halves of the wiring
connector, prising them apart with a
screwdriver if necessary (see illustration).
4Using a Allen key or hexagon bit, unscrew
the bolt securing the wheel sensor to its
mounting bracket, then carefully lever the
sensor from the bracket using a screwdriver
(see illustration). Recover the seal ring.
Refitting
5Examine the condition of the seal ring, and
renew if necessary.
6Refitting is a reversal of removal,
remembering the following points.
7Smear a little grease on the sensor casing
before fitting it to the bracket.
8Do not fully tighten the roadwheel bolts until
the vehicle is resting on its wheels.
9Check that the ABS warning lamp
extinguishes when first starting the engine
after a wheel sensor has been removed. At
9•16Braking system
20.4 ABS hydraulic modulator (cover
removed)
1 Wiring harness
clamp screws2 Earth lead
3 Relays
21.3 Front wheel sensor wiring under
wheelarch - DOHC model
1 ABS sensor connector
2 Disc pad wear sensor wiring connector
21.4 ABS front wheel sensor securing bolt
(arrowed) - DOHC model20.7 ABS hydraulic modulator securing
screws (arrowed)

the earliest opportunity, take the vehicle to a
Vauxhall dealer, and have the complete
system tested, using the dedicated ABS test
equipment.
Rear wheel sensor
Removal
10Disconnect the battery negative lead.
11Where applicable, remove the wheel trim,
then loosen the relevant rear roadwheel bolts
and chock the front wheels. Jack up the rear
of the vehicle, and support on axle stands
(see “Jacking and Vehicle Support”)
positioned under the body side members.
Remove the roadwheel.
12Unclip the sensor wiring connector from
the retaining clip on the rear underbody, then
separate the two halves of the wiring
connector, prising them apart with a
screwdriver if necessary (see illustration).
13Note the routing of the sensor wiring, and,
where applicable, release it from the clips on
the underbody.
14Using a Allen key or hexagon bit, unscrew
the bolt securing the wheel sensor to the
trailing arm (or the mounting bracket on
DOHC models), then carefully lever the sensor
from its location using a screwdriver (see
illustration). Recover the seal ring.
Refitting
15Proceed as described in paragraphs 5 to 9
inclusive.
22ABS electronic control
module - removal and refitting
3
Note: Refer to Section 2 before proceeding
ABS-2E systems
Removal
1Ensure that the ignition is switched off, then
disconnect the battery negative lead.
2The control module is located under a
cover in the passenger sill, to the left-hand
side of the seat.
3Extract the three securing screws, and lift
the cover from the control module. Note that
two of the screws are covered by plastic trim
plugs. 4Lift the control module from its recess, then
release the retaining clip and disconnect the
module wiring plug. Withdraw the module
(see illustrations).
Refitting
5Refitting is a reversal of removal.
6Check that the ABS warning lamp
extinguishes when first starting the engine
after the module has been removed. At the
earliest opportunity, take the vehicle to a
Vauxhall dealer, and have the complete
system tested, using the dedicated ABS test
equipment.
ABS-2EH systems
Removal
7Ensure that the ignition is switched off, then
disconnect the battery negative lead.
8Remove the cover from the hydraulic
modulator.
9Disconnect both the wiring harness and
solenoid valve connectors.
10Relays can only be removed from control
units that have slanted covers (see
illustration). The relays for the solenoid valve
and pump motor, if removable, can now be
removed. If the unit has a flat cover, and is
faulty, the whole unit will have to be replaced.
11Undo fixing bolts and remove the control
unit.
Refitting
12Refitting is a reversal of removal. Refer
also to paragraph 6.
23ABS relays (ABS-2E systems
only) - removal and refitting
2
Note: Refer to Section 2 before proceeding.
For ABS-2EH system relays, refer to
paragraphs 7 to 12, in Section 22.
Solenoid valve and pump motor
relays
Removal
1The solenoid valve and pump motor relays
are mounted on the hydraulic modulator.
2Disconnect the battery negative lead.
3Remove the securing screw and withdraw
the plastic cover from the hydraulic
modulator.
4Pull out the appropriate relay. The small
relay is for the solenoid valve, and the large
relay is for the pump motor.
Refitting
5Refitting is a reversal of removal.
6Check that the ABS warning lamp
extinguishes when first starting the engine
after a relay has been removed. At the earliest
opportunity, take the vehicle to a Vauxhall
dealer, and have the complete system tested,
using the dedicated ABS test equipment.
Surge arrester relay
Removal
7The surge arrester relay is located in the
relay box at the left rear of the engine
compartment.
Braking system 9•17
22.4A Lift out the ABS control module . . .22.10 ABS-2EH control unit
1 Slanted cover type 2 Flat cover type22.4B . . . and release the wiring plug
retaining clip - ABS-2E system
21.14 ABS rear wheel sensor (arrowed) -
DOHC model21.12 ABS rear wheel sensor wiring
connectors (arrowed) on rear underbody -
DOHC model`
9

8Disconnect the battery negative lead.
9Unclip the lid and open the relay box, then
pull out the relay (see illustration).
Refitting
10Refitting is a reversal of removal, with
reference to paragraph 6.
24Rear brake pressure-
proportioning valves -
removal and refitting
4
Note: Refer to the note at the beginning of
Section 3 before proceeding. Note also that
the valve must only be renewed in pairs, and
both valves must be of the same calibration.
Ensure that correct type of valves are fitted.
The bodies have been stamped for easier
identification.
Master cylinder-mounted valves
Removal
1Remove the brake fluid reservoir cap, and
secure a piece of polythene over the filler
neck with a rubber band, or by refitting the
cap. This will reduce the loss of fluid during
the following procedure.
2Locate a container beneath the master
cylinder, to catch the brake fluid that will be
released.
3Identify the two lower brake pipes for
position, then unscrew the union nuts and
disconnect the pipes from the proportioning
valves in the base of the master cylinder. Plug
the open ends of the pipes to prevent dirt
ingress.
4Unscrew the proportioning valves from the
master cylinder, and plug the open ends of
the cylinder to prevent dirt ingress.
Refitting
5Refitting is a reversal of removal, but on
completion, remove the polythene from the
brake fluid reservoir filler neck, and bleed the
complete hydraulic system, as described in
Section 3.
Rear underbody-mounted valves
Removal
6Proceed as described in paragraph 1.
7Chock the front wheels, then jack up the
rear of the vehicle, and support securely on
axle stands (see “Jacking and Vehicle
Support”) positioned under the body side
members.
8Working under the rear of the vehicle,
unscrew the union nut and disconnect the
brake pipe from one of the valves. Be
prepared for fluid spillage, and plug the open
end of the pipe to prevent dirt ingress and
further fluid spillage.
9Similarly, disconnect the flexible hose from
the valve.
10Pull the valve retaining clip from the
bracket on the underbody, noting that on
certain models, the retaining clip also secures
the ABS sensor wiring, and withdraw the valve
(see illustration).
11Repeat the procedure for the other valve.
Refitting
12Proceed as described in paragraph 5.
25Brake fluid pipes and hoses
- general, removal and refitting
4
Note: Refer to the note at the beginning of
Section 3, before proceeding.
General
1When checking the condition of the
system’s pipes and/or hoses, carefully check
that they do not foul other components such
as the power steering gear pipes (where
applicable), so that there is no risk of the
pipes chafing. If necessary use clips or ties to
secure braking system pipes and hoses well
clear of other components.
Rigid pipes
Removal
2Some of the commonly used brake pipes
can be obtained from Vauxhall parts dealers,
ready-formed and complete with unions, but
other brake pipes must be prepared using
4.75 mm (0.19 in) diameter brake pipe. Kits for
making the brake pipes can be obtained from
certain motor accessory shops.
3Before removing a brake pipe, remove the
brake fluid reservoir cap, and secure a piece
of polythene over the filler neck with a rubber
band, or by refitting the cap. This will reduce
the loss of fluid when the pipe is
disconnected.4Jack up the vehicle, and support securely
on axle stands (see “Jacking and Vehicle
Support”) positioned under the body side
members.
5To remove a brake pipe, unscrew the
unions at each end, and release the pipe from
the retaining clips.
Refitting
6Refitting is a reversal of removal, taking
care not to overtighten the unions.
7On completion, remove the polythene from
the brake fluid reservoir filler neck, and bleed
the relevant hydraulic circuit(s), as described
in Section 3.
Flexible hoses
Removal
8Proceed as described previously for the
rigid pipes, but note that a flexible pipe must
never be installed twisted, although a slight
“set” is permissible to give it clearance from
adjacent components.
Refitting
9When reconnecting a flexible hose to a
front brake caliper, note that the sealing rings
on the union bolt must be renewed.
26Handbrake - adjustment
2
Models with rear drum brakes
1The handbrake will normally be kept in
correct adjustment by the self-adjusting
action of the rear brake shoes. However, due
to cable stretch over a period of time, the
travel of the handbrake lever may become
excessive, in which case the following
operations should be carried out.
2Chock the front wheels, jack up the rear of
the vehicle, and support securely on axle
stands (see “Jacking and Vehicle Support”)
positioned under the body side members.
3Fully release the handbrake.
4Turn the knurled nut on the cable adjuster
(mounted on the torsion beam), until the brake
shoes can just be heard to rub when the rear
wheels are turned by hand in the normal
direction of rotation (see illustration).
9•18Braking system
23.9 ABS surge arrester relay (arrowed)
26.4 Handbrake cable adjuster. Knurled
nut arrowed - all SOHC models24.10 Brake pressure-proportioning valve
on rear underbody - DOHC model
1 Valve 2 Retaining clip

4B
General
Injection system type:
C16 NZ, C16 NZ2, X16 SZ and C18 NZ . . . . . . . . . . . . . . . . . . . . . . . Multec Central Fuel Injection
20 NE, C20 NE and 20 SEH, (up to 1990) . . . . . . . . . . . . . . . . . . . . . Motronic M4.1
20 NE, C20 NE and 20 SEH, (from 1990) . . . . . . . . . . . . . . . . . . . . . . Motronic M1.5
20 XEJ and C20 XE, (up to 1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . Motronic M2.5
C20 XE (from 1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Motronic M2.8
X20 XEV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Simtec 56.1
Fuel tank capacity:
All models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63.0 ± 2 litres
Fuel octane rating *
Leaded . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98 RON (4-star)
Unleaded (refer to Chapter 5) * . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 RON (Premium)
* Note
: Models fitted with a catalytic converter (engine code prefixed by ‘C’ or ‘X’), must only be operated on unleadedfuel.
Idle settings
Idle speed:
C16 NZ and X16 SZ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 850 ± 80 rpm
C16 NZ2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 880 ± 80 rpm
C18 NZ
Manual transmission models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 880 ± 80 rpm
Automatic transmission models . . . . . . . . . . . . . . . . . . . . . . . . . . . 830 ± 80 rpm
20 NE, C20 NE and 20 SEH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 800 ± 80 rpm
20 XEJ and C20 XE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 940 ± 80 rpm
X20 XEV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 850 ± 160 rpm
Note:Idle speed adjustment is not possible on these models, for information only
Chapter 4 Part B:
Fuel and exhaust systems - fuel injection models
Air box - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
Air cleaner - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
Air filter element - renewal . . . . . . . . . . . . . . . . . . . . . . . .See Chapter 1
Airflow meter (if fitted) - removal and refitting . . . . . . . . . . . . . . . . . .25
Air mass meter (if fitted) - removal and refitting . . . . . . . . . . . . . . . . .26
Air temperature sensor (later models) - removal and refitting . . . . . . .7
Air temperature control - description and testing . . . . . . . . . . . . . . . .6
Depressurising the fuel system - general . . . . . . . . . . . . . . . . . . . . . . .8
Electronic Control Unit (ECU) - removal and refitting . . . . . . . . . . . . .35
Fuel filter (‘In-tank’ fuel pump models) - removal and refitting . . . . . .10
Fuel filter (‘Out-of-tank’ fuel pump models) - removal and refitting . . .9
Fuel flow damper - removal and refitting . . . . . . . . . . . . . . . . . . . . . .18
Fuel injection system - precautions . . . . . . . . . . . . . . . . . . . . . . . . . . .2
Fuel injector (Multec system) - removal and refitting . . . . . . . . . . . . .29
Fuel injector (Multec system) - testing . . . . . . . . . . . . . . . . . . . . . . . .30
Fuel injectors (except Multec system) - removal and refitting . . . . . .28
Fuel pressure regulator - removal and refitting . . . . . . . . . . . . . . . . .21
Fuel pump - testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
Fuel pump (‘In-tank’ fuel pump models) - removal and refitting . . . .13
Fuel pump (‘Out-of-tank’ fuel pump models) - removal and refitting .12
Fuel pump relay - renewal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14Fuel tank - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
Fuel tank filler pipe - removal and refitting . . . . . . . . . . . . . . . . . . . . .15
Fuel tank sender unit - removal and refitting . . . . . . . . . . . . . . . . . . .17
General description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
Hot film mass airflow meter - removal and refitting . . . . . . . . . . . . . .27
Idle air control stepper motor - removal and refitting . . . . . . . . . . . . .33
Idle mixture - checking and adjustment . . . . . . . . . . . . . . . . . . . . . . .20
Idle speed adjuster - removal and refitting . . . . . . . . . . . . . . . . . . . . .22
Inlet manifold (DOHC models) - removal and refitting . . . . . . . . . . . .40
Inlet manifold (SOHC with Multec) - removal and refitting . . . . . . . . .39
Inlet manifold (SOHC without Multec) - removal and refitting . . . . . .38
Knock sensor and module (X16 SZ models) - removal and refitting .36
Knock sensor (Simtec system) - removal and refitting . . . . . . . . . . . .37
System testing - general . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
Throttle body (except Multec system) - removal and refitting . . . . . .31
Throttle body (Multec system) - removal and refitting . . . . . . . . . . . .32
Throttle cable - removal, refitting and adjustment . . . . . . . . . . . . . . .19
Throttle pedal - removal and refitting . . . . . . . . . . . . . .See Chapter 4A
Throttle position sensor - removal and refitting . . . . . . . . . . . . . . . . .23
Throttle potentiometer - removal and refitting . . . . . . . . . . . . . . . . . .34
Throttle valve potentiometer - removal and refitting . . . . . . . . . . . . .24
4B•1
Specifications Contents
Easy,suitable for
novice with little
experienceFairly easy,suitable
for beginner with
some experienceFairly difficult,
suitable for competent
DIY mechanic
Difficult,suitable for
experienced DIY
mechanicVery difficult,
suitable for expert DIY
or professional
Degrees of difficulty
54321

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

4B
13Manipulate the air inlet tube to release the
securing lugs from the front body panel. This
is a tricky operation, and patience will be
required. For improved access, the headlamp
can be removed, as described in Chapter 12.
Refitting
14Refitting of all components is a reversal of
removal, noting that the air cleaner element
fits with the rubber locating flange uppermost.
5Air box - removal and refitting
2
Removal
1The air box, if fitted, is secured by two or
three bolts to the top of the throttle body.
Take note of the routing and connections of
the inlet air temperature control system
vacuum pipes.
2Disconnect the engine breather hose from
the air box and the vacuum pipe from the
rearmost of the throttle body’s three unions
(see illustration).
3Do not lose the sealing ring as the air box is
withdrawn.
Refitting
4On refitting, ensure that the sealing ring is
seated correctly in the slot in the underside of
the air box, tighten the screws, and reconnect
the vacuum pipe and breather hose (see
illustrations).
6Air temperature control -
description and testing
3
Description
1Fitted to models with Multec systems, air
temperature is controlled by a thermac switch
(thermostat), mounted in the air box. When
the engine is started from cold, the switch is
closed to allow inlet manifold depression to
act on the air temperature control valve in the
air cleaner assembly. This uses a vacuum
servo in the valve assembly to draw a flap
valve across the cold air inlet thus allowing
only (warmed) air from the exhaust manifold to
enter the air cleaner.2As the temperature of the exhaust warmed
air in the air box rises, a bi-metallic strip in the
thermac switch deforms. This opens the
switch to shut off the depression in the air
temperature control valve. The flap is then
lowered gradually across the hot air inlet. Until
the engine is fully warmed up to normal
operating temperature, only cold air from the
front of the vehicle is entering the air cleaner.
Testing
3To check the system, allow the engine to
cool down completely, then remove the air
cleaner cover; the flap valve should be
securely seated across the hot air inlet. Start
the engine. The flap should immediately rise to
close off the cold air inlet. It should then lower
steadily as the engine warms until it is
eventually seated across the hot air inlet again.
4To check the thermac switch, disconnect
the control valve vacuum pipe from the switch
union (on the rear face of the air box) when the
engine is running. With the engine cold, full
inlet manifold depression should be felt
sucking at the union; none at all should be felt
when the engine is fully warmed up.
5To check the air temperature control valve,
remove the air cleaner cover; the flap valve
should be securely seated across the hot air
inlet. Disconnect the control valve vacuum
pipe from the switch union on the rear face of
the air box and suck hard on its end; the flap
should rise to shut off the cold air inlet.
6If either component is faulty, it must be
renewed. This means renewing the air cleaner
lower casing to obtain a new air temperature
control valve, or renewing the air box in the
case of the thermac switch.
7Air temperature sensor (later
models) - removal and
refitting
2
Removal
1Disconnect the battery negative lead.
2Disconnect the wiring plug at the inlet air
temperature sensor.
3Release the hose clips and remove the air
trunking then remove the inlet air temperature
sensor from the trunking.
Refitting
4Refitting is a reversal of removal but ensure
that the air trunking is connected to the
airflow meter as shown (see illustration).
8Depressurising the fuel
system - general
2
General
1The fuel system consisting of the
tank-mounted fuel pump, the fuel filter, the
fuel injector and the pressure regulator in the
throttle body. Metal pipes and flexible hoses
of the fuel lines connect these components.
All these contain fuel that will be under
pressure while the engine is running and/or
while the ignition is switched on.
2The pressure will remain for some time after
the ignition has been switched off and must
be relieved before any of these components
are disturbed.
3Remove either the fuel pump fuse (num-
ber 11) or the fuel pump relay and start the
engine. Allow the engine to idle until it cuts
out. Turn the engine over once or twice on the
starter to ensure that all pressure is released,
then switch off the ignition.
4Do not forget to refit the fuse or relay when
work is complete.
Fuel and exhaust systems - fuel injection models 4B•5
5.4B Do not overtighten the air box
screws
7.4 Removing the intake air temperature
sensor from the air trunking - later models
5.4A Ensure the sealing ring is located in
the air box groove5.2 Vacuum pipe connections to air box
A To throttle body B To air cleaner
Warning: The following
procedures will merely relieve
the pressure in the fuel system.
Remember that fuel will still be
present in the system components, so
take precautions before disconnecting
any of them. Refer to Section 2.