ECO mode JAGUAR XJ6 1997 2.G Repair Manual

6If the voltage is 6 volts, the element is okay
(there is no break). If the voltage is 12 volts,
the element is broken between the centre
of the element and the positive end. If the
voltage is 0 volts the element is broken
between the centre of the element and earth.
7To find the break, place the voltmeter
positive lead against the defogger positive
terminal. Place the voltmeter negative lead
with the foil strip against the heating element
at the positive terminal end and slide it toward
the negative terminal end. The point at which
the voltmeter deflects from zero to several
volts is the point at which the heating element
is broken (see illustration).
Repair
8Repair the break in the element using a
repair kit specifically recommended for this
purpose.
9Prior to repairing a break, turn off the system
and allow it to cool off for a few minutes.
10Lightly buff the element area with fine
steel wool, then clean it thoroughly with
rubbing alcohol.
11Use masking tape to mask off the area
being repaired.
12Thoroughly mix the epoxy, following the
instructions provided with the repair kit.
13Apply the epoxy material to the slit in the
masking tape, overlapping the undamaged
area about 3/4-inch on either end (see
illustration).
14Allow the repair to cure for 24 hours before
removing the tape and using the system.
17 Headlights- renewal
1
Warning: Later models are
equipped with halogen gas-filled
headlight bulbs which are underpressure and may shatter if the surface is
damaged or the bulb is dropped. Wear eye
protection and handle the bulbs carefully,
grasping only the base whenever possible.
Do not touch the surface of the bulb with
your fingers because the oil from your skin
could cause it to overheat and fail
prematurely. If you do touch the bulb
surface, clean it with rubbing alcohol.
Sealed beam units
1Remove the radiator grille (see Chapter 11).
2Detach the headlight bezel trim cover (see
illustration).
3Remove the headlight bezel (see
illustrations).
4Remove the screws which secure the
retaining ring and withdraw the ring. Support
the light as this is done (see illustration).
Body electrical system 12•9
12
16.13 Apply masking tape to the inside of
the window at the damaged area, then
brush on the special conductive coating17.2 Remove the screws (arrowed) and
detach the headlight bezel trim cover
17.3a Remove the two retaining screws
at the top and the one in the grille opening
(arrowed)17.3b The retaining screw at the
outside lower corner can be accessed
from under the bumper
3261 Jaguar XJ6 16.5 To determine if a heating element has broken, check the
voltage at the centre of each element. If the voltage is 6-volts, the
element is unbroken; if the voltage is 12-volts, the element is
broken between the centre and the positive end. If there is no
voltage, the element is broken between the centre and earth
16.7 To find the break, place the voltmeter positive lead against
the heated window positive terminal, place the voltmeter negative
lead with the foil strip against the heating element at the positive
terminal end and slide it toward the negative terminal end -
the point at which the voltmeter reading changes abruptly is the
point at which the element is broken

5Pull the headlight out slightly and
disconnect the electrical connector from the
rear of the light, then remove the light from the
vehicle.
6To refit, position the new unit close enough
to connect the electrical connector. Make
sure that the numbers moulded into the lens
are at the top.
7Refit and tighten the retaining ring. Test the
headlight operation.
8The remainder of the refitting is the reverse
of removal.
Halogen gas-filled bulbs
9Disconnect the electrical connector from
the bulb assembly. Rotate the headlight bulb
connector 1/4-turn anti-clockwise (viewed
from the rear) (see illustration).
10Withdraw the bulb assembly from the
headlight housing.
11Without touching the glass with your bare
fingers (see the Warningat the start of the
Section), insert the new bulb assembly into
the headlight housing and rotate the bulb
socket 1/4-turn clockwise to refit it.
12Plug in the electrical connector and test
headlight operation.
18 Headlights- adjustment
5
Note:The following procedure is intended for
emergency use only, and we strongly
recommend that the headlight aim is only
checked using optical beam-setting
equipment. It is important that the headlights
are aimed correctly. If adjusted incorrectly
they could blind the driver of an oncoming
vehicle and cause a serious accident or
seriously reduce your ability to see the road.
The headlights should be checked for proper
aim every 12 months and any time a new
headlight is installed or front end body work is
performed.
1Adjustment should be made with the
vehicle sitting level, the petrol tank half-full
and no unusually heavy load in the vehicle.2Early models with sealed beam headlights
have four adjusting knobs protruding through
the backside of the radiator support. The
vertical (up and down) adjustment knobs are
located above the headlight and the horizontal
(left to right) adjusting knobs are located
below the headlight (see illustration).
3On later models with halogen bulbs,
adjustments are made in the same manner as
described in the previous step, except there
are only two adjusting knobs which tilt the
headlight housing to the desired angle.
4If the headlight housing has been replacedor the vehicle has suffered front-end damage,
refer to following procedure.
5This method requires a blank wall, masking
tape and a level floor.
6Position masking tape vertically on the wall
in reference to the vehicle centreline and the
centrelines of both headlights (see
illustration).
7Position a horizontal tape line in reference
to the centreline of all the headlights. Note:It
may be easier to position the tape on the wall
with the vehicle parked only a few inches
away.
12•10 Body electrical system
3261 Jaguar XJ618.2 The headlight horizontal
adjustment knob (A) is located at the
top of the headlight and the vertical
adjustment knob (B) is below the headlight
17.4 Loosen the retaining ring screws
(arrowed) a few turns - rotate the retaining
ring anti-clockwise to remove it17.9 Disconnect the electrical connector
and rotate the bulb assembly 1/4-turn
anti-clockwise
18.6 Headlight
adjustment details

Later models are equipped with a
Supplemental Restraint System (SRS), more
commonly known as an airbag. This system is
designed to protect the driver, and on 1994
models, the passenger from serious injury in
the event of a head-on or frontal collision. It
consists of an airbag module in the centre of
the steering wheel and a passenger airbag
module on the right side of the dash above
the glove box on 1994 models.
The airbag modules contain an inflater and
a sensor assembly which activates from
impact energy that is transmitted through the
body and steering column upon impact or
collision.
DO NOT try to dismantle or remove any
component in the vicinity of the steering
column or instrument panel on models
equipped with air bags. Serious personalinjury or damage may result. The
manufacturer recommends that, on airbag
equipped models, service which requires
removal of any component in the vicinity of
the instrument panel or steering column
should be left to a dealer service department
or other properly equipped repair facility
because of the special tools and techniques
required to disable the air bag system.
29 Wiring diagrams-
general information
Since it isn’t possible to include a complete
wiring diagram for every year covered by this
manual, the following diagrams are those that
are typical and most commonly needed.Prior to diagnosing any circuits, check the
fuse and circuit breakers (if equipped) to make
sure they are in good condition. Make sure
the battery is properly charged and has clean,
tight cable connections (see Chapter 1).
When checking the wiring system, make
sure that all electrical connectors are clean,
with no broken or loose pins. When
unplugging an electrical connector, do not
pull on the wires, only on the connector
housings themselves.
Body electrical system 12•15
12
3261 Jaguar XJ6 Wiring diagrams commence overleaf

3261 Jaguar XJ6
Dimensions and weights . . . . . . . . . . . . . . . . . . .REF•1
Jacking and vehicle support . . . . . . . . . . . . . . . .REF•1
Radio/cassette unit anti-theft system . . . . . . . . .REF•1
Conversion factors . . . . . . . . . . . . . . . . . . . . . . .REF•2
Use of English . . . . . . . . . . . . . . . . . . . . . . . . . . .REF•3
Buying spare parts . . . . . . . . . . . . . . . . . . . . . . . .REF•4
Vehicle identification . . . . . . . . . . . . . . . . . . . . . .REF•4General repair procedures . . . . . . . . . . . . . . . . .REF•5
Tools and working facilities . . . . . . . . . . . . . . . . .REF•6
MOT test checks . . . . . . . . . . . . . . . . . . . . . . . . .REF•8
Fault finding . . . . . . . . . . . . . . . . . . . . . . . . . . . .REF•12
Glossary of technical terms . . . . . . . . . . . . . . . .REF•18
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .REF•22
Dimensions and weights
Note:All figures are approximate, and may vary according to model. Refer to manufacturer’s data for exact figures.
Dimensions
Overall length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4988 mm
Overall width (including mirrors) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2015 mm
Overall height (unladen) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1358 mm
Wheelbase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2870 mm
Weights
Kerb weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1770 kg
Maximum gross vehicle weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2190 kg
Maximum towing weight:
Braked trailer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1500 kg
Unbraked trailer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 750 kg
Maximum axle load:
Front axle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1050 kg
Rear axle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1170 kg
Maximum roof rack load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 kg
ReferenceREF•1
Radio/cassette unit anti-theft system - precaution
Some models are equipped with an audio
system which includes an anti-theft feature, to
deter thieves. If the power source to the unit is
cut, the anti-theft system will activate. Even if
the power source is immediately reconnected,
the radio/cassette unit will not function untilthe correct security code has been entered.
Therefore if you do not know the correct
security code for the unit, do notdisconnect
the battery negative lead, or remove the
radio/cassette unit from the vehicle.The procedure for reprogramming a unit
that has been disconnected from its power
supply varies from model to model - consult
the handbook supplied with the unit for
specific details or refer to your Jaguar dealer. The jack supplied with the vehicle tool kit
should only be used for changing the
roadwheels - see “Wheel changing”at the
front of this manual. When carrying out any
other kind of work, raise the vehicle using a
hydraulic (or “trolley”) jack, and always
supplement the jack with axle stands
positioned under the vehicle jacking points.
To raise the front of the vehicle, place a
block of wood on the jack head and positionthe jack underneath the centre of the front
crossmember. Lift the vehicle to the required
height and support it on axle stands
positioned underneath the vehicle jacking
points on the sills.
To raise the rear of the vehicle, place a
block of wood on the jack head and position
the jack underneath the centre of the rear
crossmember. Lift the vehicle to the required
height and support it on axle standspositioned underneath the vehicle jacking
points on the sills.
The jack supplied with the vehicle locates in
the jacking points on the sills. Ensure that the
jack head is correctly engaged before
attempting to raise the vehicle.
Neverwork under, around, or near a raised
vehicle, unless it is adequately supported in at
least two places.
Jacking and vehicle support

3261 Jaguar XJ6
REF•4Buying spare parts
Spare parts are available from many
sources, including maker’s appointed
garages, accessory shops, and motor factors.
To be sure of obtaining the correct parts, it
will sometimes be necessary to quote the
vehicle identification number. If possible, it
can also be useful to take the old parts along
for positive identification. Items such as
starter motors and alternators may be
available under a service exchange scheme -
any parts returned should be clean.
Our advice regarding spare parts is as
follows.
Officially appointed garages
This is the best source of parts which are
peculiar to your car, and which are not
otherwise generally available (eg, badges,
interior trim, certain body panels, etc). It is
also the only place at which you should buy
parts if the vehicle is still under warranty.
Accessory shops
These are very good places to buy
materials and components needed for themaintenance of your car (oil, air and fuel
filters, light bulbs, drivebelts, greases, brake
pads, touch-up paint, etc). Components of
this nature sold by a reputable shop are
usually of the same standard as those used
by the car manufacturer.
Besides components, these shops also sell
tools and general accessories, usually have
convenient opening hours, charge lower
prices, and can often be found close to home.
Some accessory shops have parts counters
where components needed for almost any
repair job can be purchased or ordered.
Motor factors
Good factors will stock all the more
important components which wear out
comparatively quickly, and can sometimes
supply individual components needed for the
overhaul of a larger assembly (eg, brake seals
and hydraulic parts, bearing shells, pistons,
valves). They may also handle work such as
cylinder block reboring, crankshaft regrinding,
etc.
Tyre and exhaust specialists
These outlets may be independent, or
members of a local or national chain. They
frequently offer competitive prices when
compared with a main dealer or local garage,
but it will pay to obtain several quotes before
making a decision. When researching prices,
also ask what “extras” may be added - for
instance fitting a new valve and balancing the
wheel are both commonly charged on top of
the price of a new tyre.
Other sources
Beware of parts or materials obtained from
market stalls, car boot sales or similar outlets.
Such items are not invariably sub-standard,
but there is little chance of compensation if
they do prove unsatisfactory. In the case of
safety-critical components such as brake
pads, there is the risk of financial loss, and
also of an accident causing injury or death.
Second-hand parts or assemblies obtained
from a car breaker can be a good buy in some
circumstances, but this sort of purchase is
best made by the experienced DIY mechanic.
Vehicle identification
Modifications are a continuing and
unpublicised process in vehicle manufacture,
quite apart from major model changes. Spare
parts manuals and lists are compiled upon a
numerical basis, the individual vehicle
identification numbers being essential to
correct identification of the part concerned.
When ordering spare parts, always give as
much information as possible. Quote the car
model, year of manufacture and registration,
chassis and engine numbers as appropriate.
The Vehicle Identification Number (VIN)
plate is attached to the base of the driver’s
door pillar left-hand wing valance and is
visible once the bonnet has been opened. The
vehicle identification (chassis) number is also
stamped onto a plate located inside the
windscreen and may also be stamped onto
the right-hand inner wing panel in the engine
compartment (see illustrations).
The trim code and paint codeare also
stamped onto the VIN plate.
The engine numberis stamped onto the
right-hand side of the cylinder block, next to
the distributor (see illustration).
The automatic transmission numberis
stamped onto a metal label attached to the
left-hand side of the transmission housing,
just above the sump (see illustration).The VIN is stamped on the right inner wing
panel of the engine compartment
The engine identification number is
stamped on the right side of the engine
block just behind the distributorThe transmission identification number is
located on the left side of the transmission
housing just above the sump
The VIN is also present on the left side of
the dashboard

3261 Jaguar XJ6
REF•6Tools and working facilities
Introduction
A selection of good tools is a fundamental
requirement for anyone contemplating the
maintenance and repair of a motor vehicle.
For the owner who does not possess any,
their purchase will prove a considerable
expense, offsetting some of the savings made
by doing-it-yourself. However, provided that
the tools purchased meet the relevant national
safety standards and are of good quality, they
will last for many years and prove an
extremely worthwhile investment.
To help the average owner to decide which
tools are needed to carry out the various tasks
detailed in this manual, we have compiled
three lists of tools under the following
headings: Maintenance and minor repair,
Repair and overhaul, and Special. Newcomers
to practical mechanics should start off with
the Maintenance and minor repairtool kit, and
confine themselves to the simpler jobs around
the vehicle. Then, as confidence and
experience grow, more difficult tasks can be
undertaken, with extra tools being purchased
as, and when, they are needed. In this way, a
Maintenance and minor repairtool kit can be
built up into a Repair and overhaultool kit over
a considerable period of time, without any
major cash outlays. The experienced do-it-
yourselfer will have a tool kit good enough for
most repair and overhaul procedures, and will
add tools from the Specialcategory when it is
felt that the expense is justified by the amount
of use to which these tools will be put.
Maintenance
and minor repair tool kit
The tools given in this list should be
considered as a minimum requirement if
routine maintenance, servicing and minor
repair operations are to be undertaken. We
recommend the purchase of combination
spanners (ring one end, open-ended the
other); although more expensive than open-
ended ones, they do give the advantages of
both types of spanner.
MCombination spanners:
Metric - 8 to 19 mm inclusive
MAdjustable spanner - 35 mm jaw (approx.)
MSpark plug spanner (with rubber insert) -
petrol models
MSpark plug gap adjustment tool - petrol
models
MSet of feeler blades
MBrake bleed nipple spanner
MScrewdrivers:
Flat blade - 100 mm long x 6 mm dia
Cross blade - 100 mm long x 6 mm dia
MCombination pliers
MHacksaw (junior)
MTyre pump
MTyre pressure gauge
MOil can
MOil filter removal tool
MFine emery cloth
MWire brush (small)
MFunnel (medium size)
Repair and overhaul tool kit
These tools are virtually essential for
anyone undertaking any major repairs to a
motor vehicle, and are additional to those
given in the Maintenance and minor repairlist.
Included in this list is a comprehensive set of
sockets. Although these are expensive, they
will be found invaluable as they are so
versatile - particularly if various drives are
included in the set. We recommend the half-
inch square-drive type, as this can be used
with most proprietary torque wrenches.
The tools in this list will sometimes need to
be supplemented by tools from the Speciallist:
MSockets (or box spanners) to cover range in
previous list (including Torx sockets)
MReversible ratchet drive (for use with
sockets)
MExtension piece, 250 mm (for use with
sockets)
MUniversal joint (for use with sockets)
MTorque wrench (for use with sockets)
MSelf-locking grips
MBall pein hammer
MSoft-faced mallet (plastic/aluminium or
rubber)
MScrewdrivers:
Flat blade - long & sturdy, short (chubby),
and narrow (electrician’s) types
Cross blade – Long & sturdy, and short
(chubby) types
MPliers:
Long-nosed
Side cutters (electrician’s)
Circlip (internal and external)
MCold chisel - 25 mm
MScriber
MScraper
MCentre-punch
MPin punch
MHacksaw
MBrake hose clamp
MBrake/clutch bleeding kit
MSelection of twist drills
MSteel rule/straight-edge
MAllen keys (inc. splined/Torx type)
MSelection of files
MWire brush
MAxle stands
MJack (strong trolley or hydraulic type)
MLight with extension lead
Sockets and reversible ratchet drive
Clutch plate alignment setPiston ring compressorSpline bit set
Valve spring compressor

3261 Jaguar XJ6
Tools and working facilitiesREF•7
Special tools
The tools in this list are those which are not
used regularly, are expensive to buy, or which
need to be used in accordance with their
manufacturers’ instructions. Unless relatively
difficult mechanical jobs are undertaken
frequently, it will not be economic to buy
many of these tools. Where this is the case,
you could consider clubbing together with
friends (or joining a motorists’ club) to make a
joint purchase, or borrowing the tools against
a deposit from a local garage or tool hire
specialist. It is worth noting that many of the
larger DIY superstores now carry a large
range of special tools for hire at modest rates.
The following list contains only those tools
and instruments freely available to the public,
and not those special tools produced by the
vehicle manufacturer specifically for its dealer
network. You will find occasional references
to these manufacturers’ special tools in the
text of this manual. Generally, an alternative
method of doing the job without the vehicle
manufacturers’ special tool is given. However,
sometimes there is no alternative to using
them. Where this is the case and the relevant
tool cannot be bought or borrowed, you will
have to entrust the work to a dealer.
MValve spring compressor
MValve grinding tool
MPiston ring compressor
MPiston ring removal/installation tool
MCylinder bore hone
MBalljoint separator
MCoil spring compressors (where applicable)
MTwo/three-legged hub and bearing puller
MImpact screwdriver
MMicrometer and/or vernier calipers
MDial gauge
MStroboscopic timing light
MDwell angle meter/tachometer
MUniversal electrical multi-meter
MCylinder compression gauge
MHand-operated vacuum pump and gauge
MClutch plate alignment set
MBrake shoe steady spring cup removal tool
MBush and bearing removal/installation set
MStud extractors
MTap and die set
MLifting tackle
MTrolley jack
Buying tools
Reputable motor accessory shops and
superstores often offer excellent quality tools
at discount prices, so it pays to shop around.
Remember, you don’t have to buy the most
expensive items on the shelf, but it is always
advisable to steer clear of the very cheap
tools. Beware of ‘bargains’ offered on market
stalls or at car boot sales. There are plenty of
good tools around at reasonable prices, but
always aim to purchase items which meet the
relevant national safety standards. If in doubt,
ask the proprietor or manager of the shop for
advice before making a purchase.
Care and maintenance of tools
Having purchased a reasonable tool kit, it is
necessary to keep the tools in a clean and
serviceable condition. After use, always wipe
off any dirt, grease and metal particles using a
clean, dry cloth, before putting the tools away.
Never leave them lying around after they have
been used. A simple tool rack on the garage
or workshop wall for items such as
screwdrivers and pliers is a good idea. Store
all normal spanners and sockets in a metal
box. Any measuring instruments, gauges,
meters, etc, must be carefully stored where
they cannot be damaged or become rusty.
Take a little care when tools are used.
Hammer heads inevitably become marked,
and screwdrivers lose the keen edge on their
blades from time to time. A little timely
attention with emery cloth or a file will soon
restore items like this to a good finish.
Working facilities
Not to be forgotten when discussing tools
is the workshop itself. If anything more than
routine maintenance is to be carried out, a
suitable working area becomes essential.
It is appreciated that many an owner-
mechanic is forced by circumstances to
remove an engine or similar item without the
benefit of a garage or workshop. Having done
this, any repairs should always be done under
the cover of a roof.
Wherever possible, any dismantling should
be done on a clean, flat workbench or table at
a suitable working height.
Any workbench needs a vice; one with a jaw
opening of 100 mm is suitable for most jobs.
As mentioned previously, some clean dry
storage space is also required for tools, as well
as for any lubricants, cleaning fluids, touch-up
paints etc, which become necessary.
Another item which may be required, and
which has a much more general usage, is an
electric drill with a chuck capacity of at least 8
mm. This, together with a good range of twist
drills, is virtually essential for fitting
accessories.
Last, but not least, always keep a supply of
old newspapers and clean, lint-free rags
available, and try to keep any working area as
clean as possible.
Stroboscopic timing light Stud extractor setCompression tester
Dial test indicator (“dial gauge”)Micrometer set

3261 Jaguar XJ6
MOT test checksREF•11
MExamine the handbrake mechanism,
checking for frayed or broken cables,
excessive corrosion, or wear or insecurity of
the linkage. Check that the mechanism works
on each relevant wheel, and releases fully,
without binding.
MIt is not possible to test brake efficiency
without special equipment, but a road test can
be carried out later to check that the vehicle
pulls up in a straight line.
Fuel and exhaust systems
MInspect the fuel tank (including the filler
cap), fuel pipes, hoses and unions. All
components must be secure and free from
leaks.
MExamine the exhaust system over its entire
length, checking for any damaged, broken or
missing mountings, security of the retaining
clamps and rust or corrosion.
Wheels and tyres
MExamine the sidewalls and tread area of
each tyre in turn. Check for cuts, tears, lumps,
bulges, separation of the tread, and exposure
of the ply or cord due to wear or damage.
Check that the tyre bead is correctly seated
on the wheel rim, that the valve is sound andproperly seated, and that the wheel is not
distorted or damaged.
MCheck that the tyres are of the correct size
for the vehicle, that they are of the same size
and type on each axle, and that the pressures
are correct.
MCheck the tyre tread depth. The legal
minimum at the time of writing is 1.6 mm over
at least three-quarters of the tread width.
Abnormal tread wear may indicate incorrect
front wheel alignment.
Body corrosion
MCheck the condition of the entire vehicle
structure for signs of corrosion in load-bearing
areas. (These include chassis box sections,
side sills, cross-members, pillars, and all
suspension, steering, braking system and
seat belt mountings and anchorages.) Any
corrosion which has seriously reduced the
thickness of a load-bearing area is likely to
cause the vehicle to fail. In this case
professional repairs are likely to be needed.
MDamage or corrosion which causes sharp
or otherwise dangerous edges to be exposed
will also cause the vehicle to fail.
Petrol models
MHave the engine at normal operating
temperature, and make sure that it is in good
tune (ignition system in good order, air filter
element clean, etc).
MBefore any measurements are carried out,
raise the engine speed to around 2500 rpm,
and hold it at this speed for 20 seconds. Allowthe engine speed to return to idle, and watch
for smoke emissions from the exhaust
tailpipe. If the idle speed is obviously much
too high, or if dense blue or clearly-visible
black smoke comes from the tailpipe for more
than 5 seconds, the vehicle will fail. As a rule
of thumb, blue smoke signifies oil being burnt
(engine wear) while black smoke signifies
unburnt fuel (dirty air cleaner element, or other
carburettor or fuel system fault).
MAn exhaust gas analyser capable of
measuring carbon monoxide (CO) and
hydrocarbons (HC) is now needed. If such an
instrument cannot be hired or borrowed, a
local garage may agree to perform the check
for a small fee.
CO emissions (mixture)
MAt the time of writing, the maximum CO
level at idle is 3.5% for vehicles first used after
August 1986 and 4.5% for older vehicles.
From January 1996 a much tighter limit
(around 0.5%) applies to catalyst-equipped
vehicles first used from August 1992. If the
CO level cannot be reduced far enough to
pass the test (and the fuel and ignition
systems are otherwise in good condition) then
the carburettor is badly worn, or there is some
problem in the fuel injection system or
catalytic converter (as applicable).
HC emissionsMWith the CO emissions within limits, HC
emissions must be no more than 1200 ppm
(parts per million). If the vehicle fails this test
at idle, it can be re-tested at around 2000 rpm;
if the HC level is then 1200 ppm or less, this
counts as a pass.
MExcessive HC emissions can be caused by
oil being burnt, but they are more likely to be
due to unburnt fuel.
Diesel models
MThe only emission test applicable to Diesel
engines is the measuring of exhaust smoke
density. The test involves accelerating the
engine several times to its maximum
unloaded speed.
Note: It is of the utmost importance that the
engine timing belt is in good condition before
the test is carried out.
M
Excessive smoke can be caused by a dirty
air cleaner element. Otherwise, professional
advice may be needed to find the cause.
4Checks carried out on
YOUR VEHICLE’S EXHAUST
EMISSION SYSTEM

3261 Jaguar XJ6
Glossary of technical termsREF•19
Catalytic converterA silencer-like device in
the exhaust system which converts certain
pollutants in the exhaust gases into less
harmful substances.
CirclipA ring-shaped clip used to prevent
endwise movement of cylindrical parts and
shafts. An internal circlip is installed in a
groove in a housing; an external circlip fits into
a groove on the outside of a cylindrical piece
such as a shaft.
ClearanceThe amount of space between
two parts. For example, between a piston and
a cylinder, between a bearing and a journal,
etc.
Coil springA spiral of elastic steel found in
various sizes throughout a vehicle, for
example as a springing medium in the
suspension and in the valve train.
CompressionReduction in volume, and
increase in pressure and temperature, of a
gas, caused by squeezing it into a smaller
space.
Compression ratioThe relationship between
cylinder volume when the piston is at top
dead centre and cylinder volume when the
piston is at bottom dead centre.
Constant velocity (CV) jointA type of
universal joint that cancels out vibrations
caused by driving power being transmitted
through an angle.
Core plugA disc or cup-shaped metal device
inserted in a hole in a casting through which
core was removed when the casting was
formed. Also known as a freeze plug or
expansion plug.
CrankcaseThe lower part of the engine
block in which the crankshaft rotates.
CrankshaftThe main rotating member, or
shaft, running the length of the crankcase,
with offset “throws” to which the connecting
rods are attached.
Crocodile clipSee Alligator clipDDiagnostic codeCode numbers obtained by
accessing the diagnostic mode of an engine
management computer. This code can be
used to determine the area in the system
where a malfunction may be located.
Disc brakeA brake design incorporating a
rotating disc onto which brake pads are
squeezed. The resulting friction converts the
energy of a moving vehicle into heat.
Double-overhead cam (DOHC)An engine
that uses two overhead camshafts, usually
one for the intake valves and one for the
exhaust valves.
Drivebelt(s)The belt(s) used to drive
accessories such as the alternator, water
pump, power steering pump, air conditioning
compressor, etc. off the crankshaft pulley.
DriveshaftAny shaft used to transmit
motion. Commonly used when referring to the
axleshafts on a front wheel drive vehicle.
Drum brakeA type of brake using a drum-
shaped metal cylinder attached to the inner
surface of the wheel. When the brake pedal is
pressed, curved brake shoes with friction
linings press against the inside of the drum to
slow or stop the vehicle.
EEGR valveA valve used to introduce exhaust
gases into the intake air stream.
Electronic control unit (ECU)A computer
which controls (for instance) ignition and fuel
injection systems, or an anti-lock braking
system. For more information refer to the
Haynes Automotive Electrical and Electronic
Systems Manual.
Electronic Fuel Injection (EFI)A computer
controlled fuel system that distributes fuel
through an injector located in each intake port
of the engine.
Emergency brakeA braking system,
independent of the main hydraulic system,
that can be used to slow or stop the vehicle if
the primary brakes fail, or to hold the vehicle
stationary even though the brake pedal isn’t
depressed. It usually consists of a hand lever
that actuates either front or rear brakes
mechanically through a series of cables and
linkages. Also known as a handbrake or
parking brake.EndfloatThe amount of lengthwise
movement between two parts. As applied to a
crankshaft, the distance that the crankshaft
can move forward and back in the cylinder
block.
Engine management system (EMS)A
computer controlled system which manages
the fuel injection and the ignition systems in
an integrated fashion.
Exhaust manifoldA part with several
passages through which exhaust gases leave
the engine combustion chambers and enter
the exhaust pipe.
F
Fan clutchA viscous (fluid) drive coupling
device which permits variable engine fan
speeds in relation to engine speeds.
Feeler bladeA thin strip or blade of hardened
steel, ground to an exact thickness, used to
check or measure clearances between parts.
Firing orderThe order in which the engine
cylinders fire, or deliver their power strokes,
beginning with the number one cylinder.
Flywheel A heavy spinning wheel in which
energy is absorbed and stored by means of
momentum. On cars, the flywheel is attached
to the crankshaft to smooth out firing
impulses.
Free playThe amount of travel before any
action takes place. The “looseness” in a
linkage, or an assembly of parts, between the
initial application of force and actual
movement. For example, the distance the
brake pedal moves before the pistons in the
master cylinder are actuated.
FuseAn electrical device which protects a
circuit against accidental overload. The typical
fuse contains a soft piece of metal which is
calibrated to melt at a predetermined current
flow (expressed as amps) and break the
circuit.
Fusible linkA circuit protection device
consisting of a conductor surrounded by
heat-resistant insulation. The conductor is
smaller than the wire it protects, so it acts as
the weakest link in the circuit. Unlike a blown
fuse, a failed fusible link must frequently be
cut from the wire for replacement.Catalytic converter
Crankshaft assembly
Accessory drivebelts
Feeler blade