Emissions JAGUAR XJ6 1997 2.G Workshop Manual

3261 Jaguar XJ6
REPAIRS & OVERHAUL
Engine and associated systems
Engine in-car repair procedures Page 2A•1
Engine removal and overhaul procedures Page 2B•1
Cooling, heating and air conditioning systems Page 3•1
Fuel and exhaust systems Page 4•1
Engine electrical systems Page 5•1
Emissions and engine cone control systems Page 6•1
Transmission
Automatic transmissionPage 7•1
DrivetrainPage 8•1
Brakes and suspension
Braking systemPage 9•1
Suspension and steering systems Page 10•1
Body equipment
Bodywork and fittingsPage 11•1
Body electrical systems Page 12•1
Wiring diagramsPage 12•16
REFERENCE
Dimensions and weights Page REF•1
Jacking and vehicle support Page REF•1
Radio/cassette unit anti-theft system - precaution Page REF•1
Conversion factorsPage REF•2
Use of EnglishPage REF•3
Buying spare parts and vehicle identification Page REF•4
General repair procedures Page REF•5
Tools and working facilities Page REF•6
MOT test checksPage REF•8
Fault findingPage REF•12
Glossary of technical terms Page REF•18
IndexPage REF•22
Contents

1 General information
1This Chapter is designed to help the home
mechanic maintain his/her vehicle for safety,
economy, long life and peak performance.
2The Chapter contains a master
maintenance schedule, followed by Sections
dealing specifically with each task in the
schedule. Visual checks, adjustments,
component renewal and other helpful items
are included. Refer to the accompanying
illustrations of the engine compartment and
the underside of the vehicle for the locations
of the various components.
3Servicing your vehicle in accordance with
the mileage/time maintenance schedule and
the following Sections will provide a planned
maintenance programme, which should result
in a long and reliable service life. This is a
comprehensive plan, so maintaining some
items but not others at the specified service
intervals, will not produce the same results.
4As you service your vehicle, you will
discover that many of the procedures can -
and should - be grouped together, because of
the particular procedure being performed, or
because of the proximity of two otherwise-
unrelated components to one another. For
example, if the vehicle is raised for any
reason, the exhaust can be inspected at the
same time as the suspension and steering
components.
5The first step in this maintenance
programme is to prepare yourself before the
actual work begins. Read through all theSections relevant to the work to be carried out,
then make a list and gather all the parts and
tools required. If a problem is encountered,
seek advice from a parts specialist, or a dealer
service department.
2 Intensive maintenance
1If, from the time the vehicle is new, the
routine maintenance schedule is followed
closely, and frequent checks are made of fluid
levels and high-wear items, as suggested
throughout this manual, the engine will be
kept in relatively good running condition, and
the need for additional work will be minimised.
2It is possible that there will be times when
the engine is running poorly due to the lack of
regular maintenance. This is even more likely
if a used vehicle, which has not received
regular and frequent maintenance checks, is
purchased. In such cases, additional work
may need to be carried out, outside of the
regular maintenance intervals.
3If engine wear is suspected, a compression
test (refer to Chapter 2) will provide valuable
information regarding the overall performance
of the main internal components. Such a test
can be used as a basis to decide on the extent
of the work to be carried out. If, for example, a
compression test indicates serious internal
engine wear, conventional maintenance as
described in this Chapter will not greatly
improve the performance of the engine, and
may prove a waste of time and money, unless
extensive overhaul work is carried out first.4The following series of operations are those
which are most often required to improve the
performance of a generally poor-running
engine:
Primary operations
a) Clean, inspect and test the battery
(Section 6).
b) Check all the engine-related fluids (refer
to “Weekly checks”).
c) Check the condition and tension of the
auxiliary drivebelt (Section 21).
d) Renew the spark plugs (Section 16).
e) Inspect the distributor cap and rotor arm
(Section 19).
f) Check the condition of the air filter, and
renew if necessary (Section 17).
g) Renew the fuel filter (Section 18).
h) Check the condition of all hoses, and
check for fluid leaks (Section 7).
i) Check the exhaust gas emissions (see
Chapter 6).
5If the above operations do not prove fully
effective, carry out the following secondary
operations:
Secondary operations
All items listed under “Primary operations”,
plus the following:
a) Check the charging system (refer to
Chapter 5).
b) Check the ignition system (refer to
Chapter 5).
c) Check the fuel system (refer to Chapter 4).
d) Renew the distributor cap and rotor arm
(Section 19).
e) Renew the ignition HT leads (Section 19).
1•6Maintenance procedures
3261 Jaguar XJ6
Every 7500 miles (12 000 km) or 6 months
3 Engine oil and filter renewal
2
1Frequent oil changes are the best
preventive maintenance the home mechanic
can give the engine, because ageing oil
becomes diluted and contaminated, which
leads to premature engine wear.
2Make sure that you have all the necessary
tools before you begin this procedure (see
illustration). You should also have plenty of
rags or newspapers handy for mopping up
any spills.
3Access to the underside of the vehicle is
greatly improved if the vehicle can be lifted on
a hoist, driven onto ramps or supported by
axle stands.
4If this is your first oil change, get under the
vehicle and familiarise yourself with the
location of the oil drain plug. The engine and
3.2 These tools are required when
changing the engine oil and filter
1 Drain pan - It should be fairly shallow in
depth, but wide in order to prevent spills
2 Rubber gloves - When removing the drain
plug and filter, it is inevitable that you will
get oil on your hands (the gloves will
prevent burns)
3 Breaker bar - Sometimes the oil drain plug
is pretty tight and a long breaker bar is
needed to loosen it
4 Socket – To be used with the breaker bar
or a ratchet (must be the correct size to fit
the drain plug)
5 Filter wrench - This is a metal band-type
wrench, which requires clearance around
the filter to be effective
6 Filter wrench - This type fits on the bottom
of the filter and can be turned with a
ratchet or breaker bar (different size
spanners are available for different types of
filters)

exhaust components will be warm during the
actual work, so try to anticipate any potential
problems before the engine and accessories
are hot.
5Park the vehicle on a level spot. Start the
engine and allow it to reach its normal
operating temperature (the needle on the
temperature gauge should be at least above
the bottom mark). Warm oil and contaminates
will flow out more easily. Turn off the engine
when it’s warmed up. Remove the oil filler cap
located next to the valve cover.
6Raise the vehicle and support it on axle
stands.
Warning: To avoid personal
injury, never get beneath the
vehicle when it is supported by
only by a jack. The jack provided
with your vehicle is designed solely for
raising the vehicle to remove and replace
the wheels. Always use axle stands to
support the vehicle when it becomes
necessary to place your body underneath
the vehicle.
7Being careful not to touch the hot exhaust
components, place the drain pan under the
drain plug in the bottom of the pan and
remove the plug (see illustration). You may
want to wear gloves while unscrewing the
plug the final few turns if the engine is really
hot.
8Allow the old oil to drain into the pan. It may
be necessary to move the pan farther under
the engine as the oil flow slows to a trickle.
Inspect the old oil for the presence of metal
shavings and chips.
9After all the oil has drained, wipe off the
drain plug with a clean rag. Even minute metal
particles clinging to the plug would
immediately contaminate the new oil.
10Clean the area around the drain plug
opening, refit the plug and tighten it securely,
but do not strip the threads.
11Move the drain pan into position under the
oil filter.
12Remove all tools, rags, etc. from under
the vehicle, being careful not to spill the oil in
the drain pan, then lower the vehicle.
13Loosen the oil filter (see illustration)by
turning it anti-clockwise with the filter wrench.
Any standard filter wrench should work. Oncethe filter is loose, use your hands to unscrew
it from the block. Just as the filter comes
away from the block, immediately tilt the open
end up to prevent the oil inside the filter from
spilling out.
Warning: The engine exhaust
pipes may still be hot, so be
careful.
14With a clean rag, wipe off the mounting
surface on the block. If a residue of old oil is
allowed to remain, it will smoke when the
block is heated up. It will also prevent the new
filter from seating properly. Also make sure
that the none of the old gasket remains stuck
to the mounting surface. It can be removed
with a scraper if necessary.
15Compare the old filter with the new one to
make sure they are the same type. Smear
some engine oil on the rubber gasket of the
new filter and screw it into place (see
illustration). Because over-tightening the
filter will damage the gasket, do not use
a filter wrench to tighten the filter. Tighten it by
hand until the gasket contacts the seating
surface. Then seat the filter by giving it an
additional 3/4-turn.
16Add new oil to the engine through the oil
filler cap next to the valve cover. Use a spout
or funnel to prevent oil from spilling onto the
top of the engine. Pour three litres of fresh oil
into the engine. Wait a few minutes to allow
the oil to drain into the pan, then check the
level on the oil dipstick (see “Weekly checks”).
If the oil level is at or near the H mark, refit the
filler cap hand tight, start the engine and allow
the new oil to circulate.
17Allow the engine to run for about a minute.
While the engine is running, look under the
vehicle and check for leaks at the sump drain
plug and around the oil filter. If either isleaking, stop the engine and tighten the plug
or filter slightly.
18Wait a few minutes to allow the oil to
trickle down into the pan, then recheck the
level on the dipstick and, if necessary, add
enough oil to bring the level to the H mark.
19During the first few trips after an oil
change, make it a point to check frequently
for leaks and proper oil level.
20The old oil drained from the engine cannot
be reused in its present state and should be
disposed of. Check with your local authority,
or with a local garage to see whether they will
accept the oil for recycling. Don’tpour used
oil into drains or onto the ground. After the oil
has cooled, it can be drained into a suitable
container (capped plastic jugs, topped
bottles, etc.) for transport to an approved
disposal site.
4 Spark plug check
2
1Spark plug renewal requires a spark plug
socket which fits onto a ratchet spanner. This
socket is lined with a rubber grommet to
protect the porcelain insulator of the spark
plug and to hold the plug while you insert it
into the spark plug hole. You will also need a
wire-type feeler gauge to check and adjust
the spark plug gap and a torque wrench to
tighten the new plugs to the specified torque
(see illustration).
2If you are replacing the plugs, purchase the
new plugs, adjust them to the proper gap and
then replace each plug one at a time. Note:
When buying new spark plugs, it’s essential
that you obtain the correct plugs for your
specific vehicle. This information can be found
in the Specifications Section at the beginning
of this Chapter, on the Vehicle Emissions
Control Information (VECI) label located on the
underside of the bonnet (where fitted)or in the
owner’s manual. If these sources specify
different plugs, purchase the spark plug type
specified on the VECI label because that
information is provided specifically for your
engine.
Every 7500 miles or 6 months 1•7
1
3.7 The oil drain plug (arrowed) is located
at the rear of the sump - use a ring
spanner or socket to remove it3.13 The oil filter is located on the left side
of the engine - use a filter wrench for
removal (tighten the new filter by hand)3.15 Lubricate the oil filter gasket with
clean engine oil before refitting the filter
3261 Jaguar XJ6
Note: It is
antisocial and
illegal to dump oil
down the drain.
To find the
location of your
local oil recycling
bank, call this
number free.

6Refit the compression gauge in the spark
plug hole (see illustration).
7Crank the engine over at least seven
compression strokes and watch the gauge.
The compression should build up quickly in a
healthy engine. Low compression on the first
stroke, followed by gradually increasing
pressure on successive strokes, indicates
worn piston rings. A low compression reading
on the first stroke, which doesn’t build up
during successive strokes, indicates leaking
valves or a blown cylinder head gasket (a
cracked cylinder head could also be the
cause). Deposits on the undersides of the
valve heads can also cause low compression.
Record the highest gauge reading obtained.
8Repeat the procedure for the remaining
cylinders and compare the results to this
Chapter’s Specifications.
9Add some engine oil (about three squirts
from a plunger-type oil can) to each cylinder,
through the spark plug hole, and repeat the
test.
10If the compression increases after the oil
is added, the piston rings are definitely worn.
If the compression doesn’t increase
significantly, the leakage is occurring at the
valves or cylinder head gasket. Leakage past
the valves may be caused by burned valve
seats and/or faces or warped, cracked or bent
valves.
11If two adjacent cylinders have equally low
compression, there’s a strong possibility that
the cylinder head gasket between them is
blown. The appearance of coolant in the
combustion chambers or the crankcase
would verify this condition.
12If one cylinder is 20 percent lower than the
others, and the engine has a slightly rough
idle, a worn exhaust lobe on the camshaft
could be the cause.
13If the compression is unusually high, the
combustion chambers are probably coated
with carbon deposits. If that’s the case, the
cylinder head(s) should be removed and
decarbonised.
14If compression is way down or varies
greatly between cylinders, it would be a goodidea to have a leak-down test performed by
an automotive repair workshop. This test will
pinpoint exactly where the leakage is
occurring and how severe it is.
5 Engine removal-
methods and precautions
If you’ve decided that an engine must be
removed for overhaul or major repair work,
several preliminary steps should be taken.
Locating a suitable place to work is
extremely important. Adequate work space,
along with storage space for the vehicle, will
be needed. If a workshop or garage isn’t
available, at the very least a flat, level, clean
work surface made of concrete or asphalt is
required.
Cleaning the engine compartment and
engine before beginning the removal
procedure will help keep tools clean and
organised.
An engine hoist or A-frame will also be
necessary. Make sure the equipment is rated
in excess of the combined weight of the
engine and transmission. Safety is of primary
importance, considering the potential hazards
involved in lifting the engine out of the vehicle.
If the engine is being removed by a novice,
a helper should be available. Advice and aid
from someone more experienced would also
be helpful. There are many instances when
one person cannot simultaneously perform all
of the operations required when lifting the
engine out of the vehicle.
Plan the operation ahead of time. Arrange
for or obtain all of the tools and equipment
you’ll need prior to beginning the job. Some of
the equipment necessary to perform engine
removal and refitting safely and with relative
ease are (in addition to an engine hoist) a
heavy duty trolley jack, complete sets of
spanners and sockets as described in the
front of this manual, wooden blocks and
plenty of rags and cleaning solvent for
mopping up spilled oil, coolant and petrol. If
the hoist must be rented, make sure that you
arrange for it in advance and perform all of the
operations possible without it beforehand.
This will save you money and time.
Plan for the vehicle to be out of use for
quite a while. A machine workshop will be
required to perform some of the work which
the do-it-yourselfer can’t accomplish without
special equipment. These shops often have a
busy schedule, so it would be a good idea to
consult them before removing the engine in
order to accurately estimate the amount of
time required to rebuild or repair components
that may need work.
Always be extremely careful when removing
and refitting the engine. Serious injury can
result from careless actions. Plan ahead, take
your time and a job of this nature, although
major, can be accomplished successfully.
6 Engine- removal and refitting
3
Note:Read through the entire Section before
beginning this procedure. It is recommended
to remove the engine and transmission from
the top as a unit, then separate the engine
from the transmission on the workshop floor. If
the transmission is not being serviced, it is
possible to leave the transmission in the
vehicle and remove the engine from the top by
itself, by removing the crankshaft damper and
tilting up the front end of the engine for
clearance,but access to the upper
bellhousing bolts is only practical when the
rear transmission mount and driveshaft have
been removed and the transmission is angled
down with a trolley jack.
Removal
1Relieve the fuel system pressure (see
Chapter 4).
2Disconnect the battery negative cable.
Caution: If the stereo in your vehicle is
equipped with an anti-theft system, make
sure you have the correct activation code
before disconnecting the battery.
3Place protective covers on the wings and
cowl and remove the bonnet (see Chapter 11).
4Remove the battery and battery tray.
5Remove the air cleaner assembly (see
Chapter 4).
6Raise the vehicle and support it securely on
axle stands. Drain the cooling system and
engine oil and remove the drivebelts (see
Chapter 1).
7Clearly label, then disconnect all vacuum
lines, coolant and emissions hoses, wiring
harness connectors and earth straps.
Masking tape and/or a touch up paint
applicator work well for marking items (see
illustration). Take instant photos or sketch
the locations of components and brackets.
8Remove the cooling fan(s) and radiator (see
Chapter 3).
9Disconnect the heater hoses.
10Release the residual fuel pressure in the
tank by removing the petrol cap, then detach
the fuel lines connecting the engine to the
chassis (see Chapter 4). Plug or cap all open
fittings.
2B•4 Engine removal and overhaul procedures
4.6 A compression gauge with a threaded
fitting for the spark plug hole is preferred
over the type that requires hand pressure
to maintain the seal - be sure to block
open the throttle valve as far as possible
during the compression check!
6.7 Label both ends of each wire and hose
before disconnecting it
3261 Jaguar XJ6

incorporated throughout. The refitting of
manifolds and external parts is all that’s
necessary. Engines in this rebuilt form are
available from Jaguar dealers, and some
independent rebuilders.
Give careful thought to which alternative is
best for you and discuss the situation with
local automotive machine shops, auto parts
dealers and experienced rebuilders before
ordering or purchasing replacement parts.
8 Engine overhaul-
dismantling sequence
1It’s much easier to dismantle and work on
the engine if it’s mounted on a portable
engine stand. A stand can often be rented
quite cheaply from an equipment rental yard.
Before the engine is mounted on a stand, the
driveplate and rear oil seal retainer should be
removed from the engine.
2If a stand isn’t available, it’s possible to
dismantle the engine with it blocked up on the
floor. Be extra careful not to tip or drop the
engine when working without a stand.
3If you’re going to obtain a rebuilt engine, all
external components must come off first, to
be transferred to the replacement engine, just
as they will if you’re doing a complete engine
overhaul yourself. These include:
Alternator and brackets
Emissions control components
Distributor, spark plug leads and spark
plugs
Thermostat and housing cover
Water pump
EFI components
Intake/exhaust manifolds
Oil filter
Engine mounts
Driveplate
Transmission adapter plate
Note:When removing the external
components from the engine, pay close
attention to details that may be helpful or
important during refitting. Note the installed
position of gaskets, seals, spacers, pins,
brackets, washers, bolts and other small items.
4If you’re obtaining a short block, which
consists of the engine block, crankshaft,
pistons and connecting rods all assembled,
then the cylinder head, sump and oil pump will
have to be removed as well from your engine
so that your short-block can be turned in to
the rebuilder as a core. See Engine rebuilding
alternativesfor additional information
regarding the different possibilities to be
considered.
5If you’re planning a complete overhaul, the
engine must be dismantled and the internal
components removed in the following order:
Intake and exhaust manifolds
Valve cover
Upper timing chain and camshaft
sprocketsCamshafts
Timing chain cover
Cylinder head
Sump
Oil pump
Piston/connecting rod assemblies
Crankshaft rear oil seal retainer
Crankshaft and main bearings
6Before beginning the dismantling and
overhaul procedures, make sure the following
items are available. Also, refer to Section 21
for a list of tools and materials needed for
engine reassembly.
Common hand tools
Small cardboard boxes or plastic bags for
storing parts
Gasket scraper
Ridge reamer
Micrometers
Telescoping gauges
Dial indicator set
Valve spring compressor
Cylinder surfacing hone
Piston ring groove-cleaning tool
Electric drill motor
Tap and die set
Wire brushes
Oil gallery brushes
Cleaning solvent
Special Jaguar tools
Engine lifting brackets (18G 1465)
Timing damper simulator (18E 1436)
Camshaft TDC tool (18G 1433)
9 Cylinder head- dismantling
2
Note: New and rebuilt cylinder heads are
available from Jaguar and some independent
rebuilders. Due to the fact that some
specialised tools are necessary for the
dismantling and inspection procedures, and
replacement parts may not be readily
available, it may be more practical and
economical for the home mechanic to
purchase a replacement cylinder head rather
than taking the time to dismantle, inspect and
recondition the original.1Cylinder head dismantling involves removal
of the intake and exhaust valves and related
components. It’s assumed that the lifters and
camshafts have already been removed (see
Part A as needed).
2Before the valves are removed, arrange to
label and store them, along with their related
components, so they can be kept separate
and reinstalled in the same valve guides they
are removed from (see illustration).
3Compress the springs on the first valve with
a spring compressor and remove the keepers
(see illustration). Carefully release the valve
spring compressor and remove the retainer,
the spring and the spring seat (if used). Note:
If your spring compressor does not have an
end (such as the one shown) with cut-outs on
the side, an adapter is available to use with a
standard spring compressor.
Caution: Be very careful not to nick or
otherwise damage the lifter bores when
compressing the valve springs.
4Pull the valve out of the cylinder head, then
remove the oil seal from the guide. If the valve
binds in the guide (won’t pull through), push it
back into the cylinder head and deburr the
area around the keeper groove with a fine file
or whetstone.
5Repeat the procedure for the remaining
valves. Remember to keep all the parts for
each valve together so they can be reinstalled
in the same locations.
6Once the valves and related components
have been removed and stored in an
organised manner, the cylinder head should
be thoroughly cleaned and inspected. If a
complete engine overhaul is being done,
finish the engine dismantling procedures
before beginning the cylinder head cleaning
and inspection process.
10 Cylinder head-
cleaning and inspection
2
1Thorough cleaning of the cylinder head(s)
and related valve train components, followed
by a detailed inspection, will enable you to
decide how much valve service work must be
2B•6 Engine removal and overhaul procedures
9.2 A small plastic bag, with an appropriate
label, can be used to store the valve train
components so they can be kept together
and reinstalled in the correct guide
3261 Jaguar XJ6
9.3 Compress the spring until the keepers
can be removed with a small magnetic
screwdriver or needle-nose pliers - use a
valve spring compressor with an adapter
(arrowed) to remove the keepers

Heating system
The heating system consists of two blower
fans, one under the dash on the right and one
on the left, and a heater core located within
the heater/air conditioning assembly which is
under the dash and behind the console.
Hoses connect the heater core to the engine
cooling system. Heater function is controlled
by the heater/air conditioning control head on
the dashboard. Hot engine coolant is
circulated through the heater core. When the
heater mode is activated, a flap door opens to
expose the heater box to the passenger
compartment. A fan switch on the control
head activates the blower motor, which forces
air through the core, heating the air.
Air conditioning system
The air conditioning system consists of a
condenser mounted in front of the radiator, an
evaporator mounted in the heat/air
conditioning assembly behind the console and
under the centre of the dash, a compressor
mounted on the engine, a filter-drier which
contains a high pressure relief valve and the
plumbing connecting all of the above.
A blower fan forces the warmer air of the
passenger compartment through the
evaporator core (sort of a radiator-in-reverse),
transferring the heat from the air to the
refrigerant. The liquid refrigerant boils off into
low pressure vapour, taking the heat with it
when it leaves the evaporator. The
compressor keeps refrigerant circulating
through the system, pumping the warmed
coolant through the condenser where it is
cooled and then circulated back to the
evaporator.
2 Antifreeze/coolant-
general information
Warning: Do not allow antifreeze
to come in contact with your
skin or painted surfaces of the
vehicle. Rinse off spills immediately withplenty of water. Antifreeze is highly toxic if
ingested. Never leave antifreeze lying
around in an open container or in puddles
on the floor; children and pets are
attracted by it’s sweet smell and may drink
it. Check with local authorities about
disposing of used antifreeze. Many
communities have collection centres which
will see that antifreeze is disposed of
safely. Never dump used antifreeze on the
ground or into drains.
Note:Non-toxic antifreeze is now
manufactured and available at local car
accessory outlets, but even these types
should be disposed of properly.
The cooling system should be filled with a
water/ethylene-glycol based antifreeze
solution, which will prevent freezing down to
at least -20° F, or lower if local climate
requires it. It also provides protection against
corrosion and increases the coolant boiling
point.
The cooling system should be drained,
flushed and refilled every 24,000 miles or
every two years (see Chapter 1). The use of
antifreeze solutions for periods of longer than
two years is likely to cause damage and
encourage the formation of rust and scale in
the system. If your tap water is “hard”, i.e.
contains a lot of dissolved minerals, use
distilled water with the antifreeze.
Before adding antifreeze to the system,
check all hose connections, because
antifreeze tends to leak through very minute
openings. Engines do not normally consume
coolant. Therefore, if the level goes down, find
the cause and correct it.
The exact mixture of antifreeze-to-water
you should use depends on the relative
weather conditions. The mixture should
contain at least 50-percent antifreeze, but
should never contain more than 70-percent
antifreeze. Consult the mixture ratio chart on
the antifreeze container before adding
coolant. Hydrometers are available at most
car accessory outlets to test the ratio
of antifreeze to water (see illustration). Use
antifreeze which meets the vehicle
manufacturer’s specifications.
3 Thermostat-
check and renewal
2
Warning: Do not attempt to
remove the radiator cap, coolant
or thermostat until the engine
has cooled completely.
Check
1Before assuming the thermostat is
responsible for a cooling system problem,
check the coolant level (Chapter 1), drivebelt
tension (Chapter 1) and temperature gauge (or
light) operation.
2If the engine takes a long time to warm up
(as indicated by the temperature gauge or
heater operation), the thermostat is probably
stuck open. Renew the thermostat.
3If the engine runs hot, use your hand to
check the temperature of the lower radiator
hose.
Warning: Do this check with the
engine off. Do not get your
hands near the fan blades. If the
hose is not hot, but the engine
is, the thermostat is probably stuck in the
closed position, preventing the coolant
inside the engine from travelling through
the radiator. Renew the thermostat. Do not
drive the vehicle without a thermostat. The
computer may stay in open loop and
emissions and fuel economy will suffer.
4If the lower radiator hose is hot, it means
that the coolant is flowing and the thermostat
is open. Consult the Troubleshootingsection
at the front of this manual for further diagnosis.
Renewal
5Disconnect the battery negative cable.
Caution: If the stereo in your vehicle is
equipped with an anti-theft system, make
sure you have the correct activation code
before disconnecting the battery.
6Drain the coolant from the radiator (see
Chapter 1).
7Remove the bolts from the thermostat
cover (see illustration). If the cover doesn’t
3•2 Cooling, heating and air conditioning systems
3261 Jaguar XJ6 2.4 An inexpensive hydrometer can be
used to test the condition of your coolant
3.7 Remove the two bolts (small arrows)
holding the thermostat cover to the
housing (large arrow)

3261 Jaguar XJ6
6
Chapter 6
Emissions and engine control systems
EGR gas temperature sensor resistance
Temperature:
212° F . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 to 100 k-ohms
400° F . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 to 8 k-ohms
662° F . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250 to 350 ohms
Torque wrench settingNm lbf ft
Crankshaft sensor bolt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 20 Air Injection Reactor (AIR) system . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Catalytic converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
CHECK ENGINE light . . . . . . . . . . . . . . . . . . . . . . . . . . . See Section 3
Crankcase ventilation system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Electronic control system and ECU . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Evaporative Emission Control (EVAP) system . . . . . . . . . . . . . . . . . . 6Exhaust Gas Recirculation (EGR) system . . . . . . . . . . . . . . . . . . . . . 6
Fuel tank cap gasket renewal . . . . . . . . . . . . . . . . . . . . . See Chapter 1
General information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Information sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
On Board Diagnosis (OBD) system -
description and fault code access . . . . . . . . . . . . . . . . . . . . . . . . . 3
6•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
1 General information
To minimise pollution of the atmosphere
from incompletely burned and evaporating
gases and to maintain good driveability and
fuel economy, a number of emission control
systems are used on these vehicles. They
include the:
Air Injection Reactor (AIR) system
Crankcase Ventilation system
Exhaust Gas Recirculation (EGR) system
Electronic Fuel Injection (EFI) system
Evaporative Emission Control (EVAP)
system
Three-way catalytic converter (TWC)
system
The sections in this chapter include general
descriptions, checking procedures within the
scope of the home mechanic and component
renewal procedures (when possible) for each
of the systems listed above.
Before assuming an emissions control
system is malfunctioning, check the fuel and
ignition systems carefully (Chapters 4 and 5).
The diagnosis of some emission control
devices requires specialised tools, equipment
and training. If checking and servicing becometoo difficult or if a procedure is beyond the
scope of your skills, consult your dealer
service department or other repair workshop.
This doesn’t mean, however, that emission
control systems are particularly difficult to
maintain and repair. You can quickly and
easily perform many checks and do most of
the regular maintenance at home with
common tune-up and hand tools. Note:The
most frequent cause of emission problems is
simply a loose or broken electrical connector
or vacuum hose, so always check the
electrical connectors and vacuum hoses first.Pay close attention to any special
precautions outlined in this chapter. It should
be noted that the illustrations of the various
systems may not exactly match the system
installed on your vehicle because of changes
made by the manufacturer during production
or from year-to-year.
The Vehicle Emissions Control Information
(VECI) label and a vacuum hose diagram are
located under the bonnet (see illustrations).
These contain important emissions specifi-
cations and setting procedures, and a
vacuum hose schematic with emissions
1.6a The Vehicle Emissions Control
Information (VECI) label shows the types of
emission control systems installed, engine
information, etc (1992 model shown)
1.6b Typical vacuum hose routing label
(1992 model shown)

components identified. When servicing the
engine or emissions systems, the VECI label
in your particular vehicle should always be
checked for up-to-date information.
2 Electronic control system
and ECU
General description
Note: These models are susceptible to ECU
damage if water is allowed to build up in the
front cowl drain and overspill into the dash
area near the computer. Inspect and clear the
front cowl drain as a regular maintenance item
to keep the water draining properly. Remove
the duckbill-type rubber hose and inspect it
for clogging, collapsing or deterioration.
1The Lucas LH Engine Management system
controls the fuel injection system by means of
a microcomputer known as the Electronic
Control unit (ECU).
2The ECU receives signals from various
sensors which monitor changing engine
operating conditions such as intake air mass,
intake air temperature, coolant temperature,
engine rpm, acceleration/deceleration,
exhaust oxygen content, etc. These signals
are utilised by the ECU to determine the
correct injection duration.
3The system is analogous to the central
nervous system in the human body: The
sensors (nerve endings) constantly relay
signals to the ECU (brain), which processes
the data and, if necessary, sends out a
command to change the operating
parameters of the engine (body).
4Here’s a specific example of how one
portion of this system operates: An oxygen
sensor, located in the exhaust manifold,
constantly monitors the oxygen content of the
exhaust gas. If the percentage of oxygen in
the exhaust gas is incorrect, an electrical
signal is sent to the ECU. The ECU takes this
information, processes it and then sends a
command to the fuel injection system telling it
to change the air/fuel mixture. This happens in
a fraction of a second and it goes on
continuously when the engine is running. The
end result is an air/fuel mixture ratio which is
constantly maintained at a predetermined
ratio, regardless of driving conditions.
5In the event of a sensor malfunction, a
backup circuit will take over to provide
driveability until the problem is identified and
fixed.
Precautions
6Follow these steps:
a) Always disconnect the power by either
turning off the ignition switch or
disconnecting the battery terminals before
removing electrical connectors.
Warning: Later models are
equipped with airbags. To
prevent accidental deployment ofthe airbag, which could cause personal
injury, DO NOT work in the vicinity of the
steering column or instrument panel. The
manufacturer recommends that, on airbag
equipped models, the following procedure
should be left to a dealer service
department or other repair workshop
because of the special tools and techniques
required to disable the airbag system.
Caution: If the stereo in your vehicle is
equipped with an anti-theft system, make
sure you have the correct activation code
before disconnecting the battery.
b) When refitting a battery, be particularly
careful to avoid reversing the positive and
negative battery cables. Also, make sure
the ignition key is in the Off position when
connecting or disconnecting the battery.
c) Do not subject EFI components,
emissions-related components or the
ECU to severe impact during removal or
refitting.
d) Do not be careless during fault diagnosis.
Even slight terminal contact can invalidate
a testing procedure and damage one of
the numerous transistor circuits.
e) Never attempt to work on the ECU or
open the ECU cover. The ECU is
protected by a government-mandated
extended warranty that will be nullified if
you tamper with or damage the ECU.
f) If you are inspecting electronic control
system components during rainy weather,
make sure that water does not enter any
part. When washing the engine
compartment, do not spray these parts or
their electrical connectors with water.
g) These models are susceptible to ECU
damage if water is allowed to build up in
the front cowl drain and overspill into the
dash area. Inspect and clear the front
cowl drain system as a regular
maintenance item to keep the water
draining properly. Remove the duckbill
type rubber hose and inspect it for
clogging, collapsing or deterioration.
ECU removal and refitting
7Disconnect the negative cable from the
battery (see Chapter 5).
Warning: Later models are
equipped with airbags. To
prevent the accidental deploy-
ment of the airbag, which could
cause personal injury, DO NOT work in the
vicinity of the steering column or
instrument panel. The manufacturer
recommends that, on airbag equipped
models, the following procedure should be
left to a dealer service department or other
repair workshop because of the special
tools and techniques required to disable
the airbag system.
Caution: If the stereo in your vehicle is
equipped with an anti-theft system, make
sure you have the correct activation code
before disconnecting the battery.8Remove the lower instrument panel on the
passenger side under the glove compartment
(see Chapter 11).
9Remove the glove compartment from the
passenger compartment (see Chapter 11).
10Remove the screws from the ECU bracket
(see illustration).
11Lower the ECU and unplug the electrical
connectors.
12Refitting is the reverse of removal.
3 On Board Diagnosis (OBD)
system- description and fault
code access
2
Note: 1990 and 1991 models may set
Code 69 erroneously. If the battery voltage
drops sufficiently and the ignition key is
switched quickly from OFF to START, battery
voltage will be lowered and during cranking
causing a delayed park/neutral signal from the
decoder module to the ECU. Check all the
battery connections and the condition of the
battery and then check the rotary switch
adjustment in Chapter 7 to remedy this code.
General information
1The ECU contains a built-in self-diagnosis
system which detects and identifies
malfunctions occurring in the network. When
the ECU detects a problem, three things
happen: the CHECK ENGINE light comes on,
the fault is identified and a diagnostic code is
recorded and stored. The ECU stores the
failure code assigned to the specific problem
area until the diagnosis system is cancelled.
Note: 1988 and 1989 models are not
equipped with long term memory. It is
possible to access the codes but the operator
must remember to NOT turn the ignition key to
the OFF position after the CHECK ENGINE
light has been noticed. The codes will be lost
and it will be necessary to start the engine and
operate the vehicle through a complete drive
cycle to allow the fault code(s) to be set once
again. Instead of turning the ignition key to the
OFF position, simply stop at position II (key
ON but engine not running) to retain the fault
codes.
6•2 Emissions and engine control systems
3261 Jaguar XJ6
2.10 The ECU is located behind the
passenger’s side glovebox near the footrest
area. Remove the mounting screws
(arrowed) and carefully lower the ECU

2The CHECK ENGINE warning light, which is
located on the instrument panel, comes on
when the ignition switch is turned to ON and
the engine is not running. When the engine is
started, the warning light should go out. If the
light remains on, the self-diagnosis system
has detected a malfunction. Note: The
CHECK ENGINE light on early models is
displayed on the dashboard VCM panel on the
right side. Later models are equipped with a
separate CHECK ENGINE light on the left side
of the instrument cluster.Note:Not all the
codes will cause the CHECK ENGINE light to
activate. When performing any fuel or
emissions systems diagnosis, always check
for codes that may be stored but not indicated
by the CHECK ENGINE light.
Obtaining fault code output
3To obtain an output of diagnostic codes,
verify first that the battery voltage is above 11
volts, the throttle is fully closed, the
transmission is in Park, the accessory
switches are off and the engine is at normal
operating temperature.
4Turn the ignition switch to ON but don’t
start the engine (Position II). Note:On 1988
and 1989 models, remember to turn the
ignition switch to position II without turning
the key to OFF.
5Press the VCM button on the display panel
(see illustration)and observe the LED display
on the dash for the designated codes. An
asterisk next to the code indicates that there
are multiple codes stored.
6The numerical values will be displayed on
the trip computer display on the dashboard.
7If there are any malfunctions in the system,
the corresponding fault codes are displayed in
numerical order, lowest to highest.
Cancelling a diagnostic code
8After the faulty component has been
repaired/renewed, the fault code(s) stored in
computer memory must be cancelled.
a) On 1988 to 1991 vehicles, simply drive
the vehicle faster than 19 mph and the
computer will automatically erase the
stored fault code from memory.b) On 1992 to 1994 models, disconnect the
negative battery lead for 30 seconds or
more to erase the stored fault codes.
Caution: If the stereo in your vehicle is
equipped with an anti-theft system, make
sure you have the correct activation code
before disconnecting the battery.
9A stored code can also be cancelled on
early models by removing the cable from the
battery negative terminal, but other items with
memory (such as the clock and radio presets)
will also be cancelled.
10If the diagnosis code is not cancelled, it
will be stored by the ECU and appear with any
new codes in the event of future trouble.
11Should it become necessary to work on
engine components requiring removal of the
battery terminal, always check to see if a
diagnostic code has been recorded before
disconnecting the battery.
4 Information sensors
Note: Refer to Chapters 4 and 5 for additional
information on the location and the diagnostic
procedures for the output actuators (ISC
motor, air supplementary valve, distributor,
amplifier, etc.) that are not directly covered in
this section.
Coolant temperature sensor
General description
1The coolant temperature sensor is a
thermistor (a resistor which varies the value of
its voltage output in accordance with
temperature changes) which is threaded into
the thermostat housing. As the sensor
temperature DECREASES, the resistance
values will INCREASE. As the sensor
Emissions and engine control systems 6•3
6
3.5 To access the self-diagnosis system
fault codes, locate the VCM button on the
dash and with the ignition key ON (engine
not running) press it to display the codes
3261 Jaguar XJ6
Fault code chart for 1988 and 1989 models
Code System affected Probable cause
1 Oxygen sensor Open oxygen sensor circuit
2 Airflow sensor Not in operating range
3 Coolant temperature sensor Not in operating range
4 Oxygen sensor System indicates full rich
5 Throttle potentiometer/airflow sensor Low throttle potentiometer signal
with high airflow sensor signal
6 Throttle potentiometer/airflow sensor High throttle potentiometer signal
with low airflow sensor signal
7 Throttle potentiometer Idle fuel adjustment failure
8 Intake air temperature sensor Open or shorted circuit in IAT sensor
harness
Fault code chart for 1990 to 1994 models
Code System affected Probable cause
11 Idle potentiometer Not in operating range
12 Airflow sensor Not in operating range
14 Coolant temperature sensor Not in operating range
16 Air temperature sensor Not in operating range
17 Throttle potentiometer Not in operating range
18 Throttle potentiometer/airflow sensor Signal resistance low
at wide open throttle
19 Throttle potentiometer/airflow sensor Signal resistance high at idle
22 Heated oxygen sensor Open or short circuit
22 Fuel pump circuit Open or short circuit
23 Fuel supply Rich exhaust Indicated
24 Ignition amplifier circuit Open or short circuit
26 Oxygen sensor circuit Lean exhaust/vacuum leak
29 ECU Self check
33 Fuel injector circuit Open or short circuit
34 Fuel injector circuit Faulty injector indicated
37 EGR solenoid circuit Short or open circuit
39 EGR circuit Faulty system operation
44 Oxygen sensor circuit Rich or lean condition
46 Idle speed control valve - (coil 1) Open or short circuit
47 Idle speed control valve - (coil 2) Open or short circuit
48 Idle speed control valve Not within specification
68 Road speed sensor Incorrect signal voltage
69 Neutral safety switch circuit Engine cranks in Drive
(adjust or renew switch)
89 Purge control valve circuit Open or short circuit

temperature INCREASES, the resistance
values will DECREASE. A failure in this sensor
circuit should set a Code 3 (1988 and 1989)
or 13 (1990 to 1994). This code indicates a
failure in the coolant temperature sensor
circuit, so in most cases the appropriate
solution to the problem will be either repair of
a connector or wire, or renewal of the sensor.
Check
2To check the sensor, measure its resistance
value (see illustration)while it is completely
cold (60 to 80° F = 1500 to 3000 ohms). Next,
start the engine and warm it up until it reaches
operating temperature. The resistance should
be lower (180 to 200° F = 280 to 350 ohms).
3If the resistance values of the coolant
temperature sensor are correct, check the
circuit for the proper signal voltage. Turn the
ignition key ON (engine not running) and
check for reference voltage with a high-
impedance digital voltmeter (see illustration).
It should be approximately 5 volts.
Renewal
Warning: Wait until the engine is
completely cool before
beginning this procedure.
4To remove the sensor, depress the locking
tabs, unplug the electrical connector, then
carefully unscrew the sensor.
Caution: Handle the coolant sensor with
care. Damage to this sensor will affect the
operation of the entire fuel injection
system.
5Before refitting the new sensor, wrap the
threads with Teflon sealing tape to prevent
leakage and thread corrosion.
6Refitting is the reverse of removal.
Oxygen sensor
Note:An oxygen sensor splash shield is
equipped on models from VIN 664941 (mid-1990) to present. This shield prevents the self
diagnosis system from setting an intermittent
and erroneous code 44. Whenever replacing
an oxygen sensor, make sure the splash shield
is in place.
General description
7These models are equipped with a heated
oxygen sensor system. The oxygen sensor is
mounted ahead of the front catalytic converter
and monitors the exhaust gases before they
are changed. The electrical heating system
incorporated into the oxygen sensor allows for
quicker warm-up time and more efficient
oxygen content monitoring. The oxygen sensor
monitors the oxygen content of the exhaust
gas stream. The oxygen content in the exhaust
reacts with the oxygen sensor to produce a
voltage output which varies from 0.1 volts (high
oxygen, lean mixture) to 0.9 volts (low oxygen,
rich mixture). The ECU constantly monitors this
variable voltage output to determine the ratio of
oxygen to fuel in the mixture. The ECU alters
the air/fuel mixture ratio by controlling the pulse
width (open time) of the fuel injectors. A mixture
ratio of 14.7 parts air to 1 part fuel is the ideal
mixture ratio for minimising exhaust emissions,
thus allowing the catalytic converter to operate
at maximum efficiency. This ratio of 14.7 to 1 is
the one which the ECU and the oxygen sensor
attempt to maintain at all times.
8The oxygen sensor produces no voltage
when it is below its normal operating
temperature of about 600° F. During this initial
period before warm-up, the ECU operates in
open loop mode.
9If the engine reaches normal operating
temperature and/or has been running for two or
more minutes, and if the oxygen sensor is
producing a steady signal voltage below
0.45 volts at 1500 or more rpm, the ECU will set
a Code 4 (1988 and 1989) or 26 (1990 to 1994).
10When there is a problem with the oxygen
sensor or its circuit, the ECU operates in theopen loop mode - that is, it controls fuel
delivery in accordance with a programmed
default value instead of feedback information
from the oxygen sensor.
11The proper operation of the oxygen
sensor depends on four conditions:
a) Electrical - The low voltages generated by
the sensor depend upon good, clean
connections which should be checked
whenever a malfunction of the sensor is
suspected or indicated.
b) Outside air supply - The sensor is
designed to allow air circulation to the
internal portion of the sensor. Whenever
the sensor is removed and installed or
renewed, make sure the air passages are
not restricted.
c) Proper operating temperature - The ECU
will not react to the sensor signal until the
sensor reaches approximately 600° F.
This factor must be taken into
consideration when evaluating the
performance of the sensor.
d) Unleaded fuel - The use of unleaded fuel
is essential for proper operation of the
sensor. Make sure the fuel you are using
is of this type.
12In addition to observing the above
conditions, special care must be taken
whenever the sensor is serviced.
a) The oxygen sensor has a permanently
attached pigtail and electrical connector
which should not be removed from the
sensor. Damage to or removal of the
pigtail or electrical connector can
adversely affect operation of the sensor.
b) Grease, dirt and other contaminants
should be kept away from the electrical
connector and the louvered end of the
sensor.
c) Do not use cleaning solvents of any kind
on the oxygen sensor.
d) Do not drop or roughly handle the sensor.
6•4 Emissions and engine control systems
3261 Jaguar XJ6 4.2 The coolant temperature sensor is in the thermostat housing.
To check the coolant temperature sensor, use an ohmmeter to
measure the resistance between the two sensor terminals
4.3 Check for reference voltage to the electrical connector for the
coolant sensor with the ignition key ON (engine not running).
It should be approximately 5.0 volts