1997 JAGUAR XJ6 check engine light

5If equipped with an automatic transmission,
disconnect the cooler lines from the radiator
(see illustrations). Disconnect the cooling fan
switch connector (see illustration 4.15).
Place a drip pan to catch the fluid and cap the
fittings. Note:The transmission oil cooler lines
enter the radiator on the left, while the power
steering cooler lines attach on the right side of
the radiator. On 1993 and 1994 models, the
cooler fittings require a spring-lock coupling
tool, normally used on fuel lines or air
conditioning lines.
6Remove the four bolts from the radiator
cowl panel and take off the panel (see
illustration).
7Lift out the radiator. Be aware of dripping
fluids and the sharp fins. Take care not to
damage the radiator fins by contact with other
parts.
8With the radiator removed, it can be
inspected for leaks, damage and internal
blockage. If repairs are necessary, have a
radiator specialist or dealer service department
perform the work, as special techniques are
required. Check the rubber mounting pads on
the bottom of the radiator (see illustration). If
they’re cracked or damaged, get new ones
before refitting the radiator.
9Bugs and dirt can be cleaned from the
radiator with compressed air and a soft brush.
Don’t bend the cooling fins as this is done.
Warning: Wear eye protection.
Refitting
10Refitting is the reverse of the removal
procedure. Be sure the rubber mounts are in
place on the bottom of the radiator.
11After refitting, fill the cooling system with
the proper mixture of antifreeze and water.
Refer to Chapter 1 if necessary.
12Start the engine and check for leaks.
Allow the engine to reach normal operating
temperature, indicated by both radiator hoses
becoming hot. Recheck the coolant level and
add more if required.
13On automatic transmission equipped
models, check and add fluid as needed and
check the power steering fluid level as well.
Expansion tank and coolant
reservoir, removal and refitting
14The expansion tank is located at the top
of the left-hand side inner wing. With the
cooling system drained below the level of the
expansion tank, remove the hoses, the
coolant level probe and the two screws
mounting it to the body (see illustration).
15Wash out and inspect the reservoir for
cracks and chafing. Renew it if damaged.16If the low-coolant level light has been
showing on the instrument panel, even when
the coolant level is correct, disconnect the
sensor’s connector and test it with an
ohmmeter (see illustration). The sensor
should be renewed if the resistance at the
connections is over 150 ohms.
Caution: Using a long-necked funnel to
add coolant can damage the sensor, which
is just below the expansion tank filler neck.
Cooling, heating and air conditioning systems 3•5
3
5.5a At the left side of the radiator,
disconnect the automatic transmission
cooler lines (small arrows) and the lower
radiator hose (larger arrow)5.5b Disconnect the power steering cooler
lines (small arrows) at the right side of the
radiator, and the upper radiator hose
(large arrow)
3261 Jaguar XJ6 5.3 Remove the clamp and the hose going
to the expansion tank
5.6 Remove the bolts (arrowed) and take
off the radiator cowl panel
5.14 The expansion tank is located on the
left inner wing
A Hose to recovery tank (where applicable)
B Hose to radiator
C Hose to thermostat housing
D Hose to water pump housing
E Mounting screws
F Low-coolant-level sensor
5.8 There are rubber mounts (arrowed)
for the radiator and the condenser -
they must be in place when these
components are reinstalled
5.16 The low-coolant-level sensor can be
tested with an ohmmeter - resistance
should be below 150 ohms - gently use a
pair of long-neck pliers to move the sensor
up and down in the tank to get a reading

17A coolant recovery bottle is used on 1988
and 1989 models, located in the passenger’s
inner wing. The plastic inner wing splash
shield must be removed for access to the
recovery bottle (see Chapter 11). Disconnect
the recovery hose and remove the mounting
screws to renew the recovery bottle (see
illustration). Models from 1990 on do not
have the recovery bottle, but do have a larger
expansion tank.
18Refitting of either expansion tank or
recovery bottle is the reverse of removal.
6 Engine oil cooler- renewal
2
1Models from 1988 through 1991 have a
engine oil cooler, mounted ahead of the
radiator. The engine’s mechanical fan draws
air through the oil cooler, cooling off hot
engine oil that is circulated from the engine by
steel tubes. Access to the cooler is with the
grille removed (refer to Chapter 11 for grille
removal).
2To renew the oil cooler, first disconnect thetwo fittings connecting the lines to the cooler
(see illustration).
Caution: The engine should be cool for this
procedure, and you should have a small
drain pan handy because the fittings are
on the bottom of the cooler and will
probably drip some oil on dismantling.
3Remove the mounting nuts to take the
cooler out of the vehicle (see illustration).
4The other ends of the oil cooler tubes
mount to a block just below the oil filter. With
a drain pan handy, remove the nut retaining
both pipes to the block.
5Refitting the oil cooler and oil lines is the
reverse of removal. When refitting the lines to
the block or the cooler, use new O-rings.7 Water pump- check
1
1A failure in the water pump can cause
serious engine damage due to overheating.
2With the engine running and warmed to
normal operating temperature, squeeze the
upper radiator hose. If the water pump is
working properly, a pressure surge should be
felt as the hose is released.
Warning: Keep hands away from
fan blades!
3Water pumps are equipped with weep or
vent holes (see illustration). If a failure occurs
in the pump seal, coolant will leak from this
hole. In most cases it will be necessary to use
a flashlight to find the hole on the water pump
by looking through the space behind the
pulley just below the water pump shaft.
4If the water pump shaft bearings fail there
may be a howling sound at the front of the
engine while it is running. Bearing wear can be
felt if the water pump pulley is rocked up anddown. Do not mistake drivebelt slippage,
which causes a squealing sound, for water
pump failure. Spray automotive drivebelt
dressing on the belts to eliminate the belt as a
possible cause of the noise.
8 Water pump and pipes-
renewal
3
Warning: Do not start this
procedure until the engine is
completely cool.
1Disconnect the negative battery cable and
drain the cooling system (see Chapter 1).
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.
2Refer to Section 4 to remove the
mechanical fan and clutch (if applicable to
your model).
3Refer to Chapter 1 for removal of the
drivebelts.
3•6 Cooling, heating and air conditioning systems
6.3 Remove the mounting nuts (arrowed)
to take the oil cooler out
7.3 Check the weep hole (arrowed) for
signs of leakage (pump removed for
clarity) - grey discolouration is normal,
large brown stains indicates seal failure
3261 Jaguar XJ6 5.17 The recovery bottle (arrowed) on 1988 and 1989 models is
located in the footwell - disconnect the hoses and the two
mounting screws
6.2 Disconnect the two metal oil lines (arrowed) where they
mount to the bottom of the cooler - use two spanners

4Refitting is the reverse of the removal
procedure.
5Run the engine and check for proper
functioning of the heater (and air conditioning,
if equipped).
Control checks
6The climate-control system uses an all-
electronic control panel that sends digital
information to the climate control computer.
There is little the home mechanic can do to
troubleshoot or test the system. The factory
recommends that diagnosis be performed at a
dealership.
7If there is a problem in just one area of
climate control, put the controls through their
entire range of operation and check the
system responses, i.e. set the controls to
COLD, the fan to low and the temperature to
65° F. In this mode the Manual LED should be
lit and the air conditioning compressor should
engage. Try all of the fan speeds and try the
temperature on HOT, then feel for warm air
coming from the ducts. Note:Between each
try of the different controls, wait 20 seconds or
so for the heater/air conditioning system to
adjust before checking for a response.
8When each control button is pushed two
times, its LED light should go on or off. Renew
the control assembly if any of the warning
lights don’t work.
9On 1988 and 1989 models, if the climate
controls do not respond to any driver input,
check with your Jaguar dealer before
renewing the ECU or control panel. A service
part is available (a resistor, #JLM 1901) that
can be installed at one of the control panel
terminals that may fix the problem without any
other parts being renewed. Instructions are
included with the part.
10Check the vacuum lines to the several
vacuum motors that operate the heater/air
conditioning functions. Look for pinched or
blocked hoses and leaks.11Each of the vacuum “servo motors” in the
system can be checked with a hand-held
vacuum pump (see illustration). Apply vacuum
and watch that the door or control it operates is
working.
12Further diagnosis of the controls or
climate control ECU are best left to a Jaguar
dealership or other qualified repair facility.
13 Air conditioning and heating
system- check and
maintenance
1
Air conditioning system
Warning: The air conditioning
system is under high pressure.
Do not loosen any hose fittings
or remove any components until
the system has been discharged. Air
conditioning refrigerant should be properly
discharged into an EPA-approved
recovery/recycling unit by a dealer service
department or an automotive air
conditioning repair facility. Always wear
eye protection when working near air
conditioning system fittings.
1The following maintenance checks should
be performed on a regular basis to ensure that
the air conditioner continues to operate at
peak efficiency:
a) Inspect the condition of the compressor
drivebelt. If it is worn or deteriorated,
renew it (see Chapter 1).
b) Check the drivebelt tension and, if
necessary, adjust it (see Chapter 1).
c) Inspect the system hoses. Look for
cracks, bubbles, hardening and
deterioration. Inspect the hoses and all
fittings for oil bubbles or seepage. If there
is any evidence of wear, damage or
leakage, renew the hose(s).d) Inspect the condenser fins for leaves,
bugs and any other foreign material that
may have embedded itself in the fins. Use
a “fin comb” or compressed air to remove
debris from the condenser.
e) Make sure the system has the correct
refrigerant charge.
2It’s a good idea to operate the system for
about ten minutes at least once a month. This
is particularly important during the winter
months because long term non-use can
cause hardening, and subsequent failure, of
the seals.
3Leaks in the air conditioning system are
best spotted when the system is brought up
to operating temperature and pressure, by
running the engine with the air conditioning
ON for five minutes. Shut the engine off and
inspect the air conditioning hoses and
connections. Traces of oil usually indicate
refrigerant leaks.
4Because of the complexity of the air
conditioning system and the special
equipment required to effectively work on it,
accurate troubleshooting of the system
should be left to a professional technician.
5If the air conditioning system doesn’t
operate at all, check the fuse panel and the air
conditioning relay (refer to Chapter 12 for
relay locations and testing). See Sections 4, 9
and 12 for electrical checks of heating/air
conditioning system components.
6The most common cause of poor cooling is
simply a low system refrigerant charge. If a
noticeable drop in cool air output occurs, the
following quick check will help you determine
if the refrigerant level is low.
Checking the refrigerant charge
7Warm the engine up to normal operating
temperature.
8Place the air conditioning temperature
selector at the coldest setting and put the
Cooling, heating and air conditioning systems 3•11
3
3261 Jaguar XJ6 12.3b Remove the four screws (three are shown here) holding the
control assembly in the control/radio housing
12.11 Check the operation of the vacuum servo motors; in this
case, vacuum is applied to the servo on the right blower case -
the flapper door (arrowed) should operate

3261 Jaguar XJ6
4
Chapter 4
Fuel and exhaust systems
Fuel system
Fuel pressure:kPa psi
Ignition ON, engine not running . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260 to 300 38 to 44
Engine idling:
Vacuum hose detached from fuel pressure regulator . . . . . . . . . . . 280 to 320 40 to 46
Vacuum hose attached to fuel pressure regulator . . . . . . . . . . . . . 210 to 260 30 to 38
Fuel system hold pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145 21
Fuel injector resistance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.0 to 3.0 ohms
Idle speed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Must be set by authorised service department
Torque wrench settingsNm lbf ft
Throttle body mounting bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 14
Fuel rail mounting bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 9 Accelerator cable - removal, refitting and adjustment . . . . . . . . . . . 10
Air cleaner assembly - removal and refitting . . . . . . . . . . . . . . . . . . . 9
Catalytic converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See Chapter 6
CHECK ENGINE light . . . . . . . . . . . . . . . . . . . . . . . . . . . See Chapter 6
Electronic Fuel Injection (EFI) system - check . . . . . . . . . . . . . . . . . . 12
Electronic Fuel Injection (EFI) system - component check
and renewal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Electronic Fuel Injection (EFI) system - general information . . . . . . . 11
Exhaust manifold - removal and refitting . . . . . . . . . . . See Chapter 2A
Exhaust system check . . . . . . . . . . . . . . . . . . . . . . . . . . See Chapter 1
Exhaust system servicing - general information . . . . . . . . . . . . . . . . 14
Fuel filter renewal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See Chapter 1Fuel level sender unit - check and renewal . . . . . . . . . . . . . . . . . . . . 5
Fuel lines and fittings - inspection and renewal . . . . . . . . . . . . . . . . 6
Fuel pressure relief . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Fuel pump - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Fuel pump/fuel pressure - check . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Fuel system check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See Chapter 1
Fuel tank - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Fuel tank cap gasket renewal . . . . . . . . . . . . . . . . . . . . . See Chapter 1
Fuel tank cleaning and repair - general information . . . . . . . . . . . . . 8
General information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Intake manifold - removal and refitting . . . . . . . . . . . . See Chapter 2A
Underbonnet hose check and renewal . . . . . . . . . . . . . . See Chapter 1
4•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
The fuel system consists of a fuel tank, an
electric fuel pump either located externally,
next to the fuel tank (1988 to 1990 models) or
in the fuel tank (1991 to 1994 models), an EFI
fuel pump relay and main relay, an inertia
switch, fuel injectors and fuel rail, an air
cleaner assembly and a throttle body unit.
Multi Point Fuel Injection (MPFI)
system
Multi point fuel injection uses timed
impulses to sequentially inject the fuel directly
into the intake port of each cylinder. Theinjectors are controlled by the Electronic
Control Unit (ECU). The ECU monitors various
engine parameters and delivers the exact
amount of fuel, in the correct sequence, into
the intake ports. The throttle body serves only
to control the amount of air passing into the
system. Because each cylinder is equipped
with an injector mounted immediately
adjacent to the intake valve, much better
control of the fuel/air mixture ratio is possible.
Fuel pump and lines
Fuel is circulated from the fuel tank to the
fuel injection system, and back to the fuel
tank, through a pair of metal lines running
along the underside of the vehicle. On early
models (1988 to 1990), an electric fuel pump
is attached to the chassis next to the fueltank. On later models (1991 to 1994), the fuel
pump and fuel level sender unit are located
inside the fuel tank. A vapour return system
routes all vapours and hot fuel back to the fuel
tank through a separate return line.
The fuel pump will operate as long as the
engine is cranking or running and the ECU is
receiving ignition reference pulses from the
electronic ignition system (see Chapter 5). If
there are no reference pulses, the fuel pump
will shut off after 2 or 3 seconds.Inertia switch
These models are equipped with an inertia
switch that is wired in the circuit between the
fuel pump relay, the ignition switch and the
fuel pump (refer to the wiring diagrams at the
end of Chapter 12). The inertia switch is a

special electrical device that provides circuit
protection by switching off the ignition and
fuel pump upon impact in the event of vehicle
collision. Later Jaguar models are equipped
with an additional specialised inertia switch.
This later device switches OFF all ignition fed
circuits, locks the fuel filler cap, locks the boot
(only if doors are locked) and unlocks the
doors if they are locked during the accident.
All these functions are directed by the inertia
switch. The inertia switch is located behind
the left kick panel. Refer to Chapter 12 for
more information.
Exhaust system
The exhaust system includes an exhaust
manifold equipped with an exhaust oxygen
sensor, a catalytic converter, an exhaust pipe,
and a silencer.
The catalytic converter is an emission
control device added to the exhaust system to
reduce pollutants. A single-bed converter is
used in combination with a three-way
(reduction) catalyst. See Chapter 6 for more
information regarding the catalytic converter.
2 Fuel pressure relief
1
Warning: Petrol is extremely
flammable, so take extra
precautions when you work on
any part of the fuel system.
Don’t smoke or allow open flames or bare
light bulbs near the work area, and don’t
work in a garage where a natural gas-type
appliance (such as a water heater or a
clothes dryer) with a pilot light is present.
Since petrol is carcinogenic, wear latex
gloves when there’s a possibility of being
exposed to fuel, and, if you spill any fuel on
your skin, rinse it off immediately with soap
and water. Mop up any spills immediately
and do not store fuel-soaked rags wherethey could ignite. The fuel system is under
constant pressure, so, if any fuel lines are
to be disconnected, the fuel pressure in
the system must be relieved first. When
you perform any kind of work on the fuel
system, wear safety glasses and have a
Class B type fire extinguisher on hand.
1Before servicing any fuel system
component, you must relieve the fuel pressure
to minimise the risk of fire or personal injury.
2Remove the fuel filler cap - this will relieve
any pressure built up in the tank.
3Remove the fuel pump relay from the main
relay panel (see illustrations). Note:These
models are equipped with a fuel pump relay
that is located in various areas of the vehicle
depending on the year. On 1988 and 1989
models, the fuel pump relay is under the
glovebox. On 1990 to 1992 models, the fuel
pump relay is in the engine compartment on
the left side, attached to the brake pedal
hanger. On 1993 models, the fuel pump relay
is in the boot. On 1994 models, it’s in the
engine compartment on the right side of the
bulkhead. Refer to the relay location charts in
Chapter 12 for additional information.
4Start the engine and wait for the engine to
stall, then turn the ignition key to Off.
Disconnect the cable from the negativeterminal of the battery before beginning any
work on the fuel 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.
5The fuel system is now depressurised.
Note:Place a rag around the fuel line before
removing any hose clamp or fitting to prevent
any residual fuel from spilling onto the engine.
3 Fuel pump/fuel pressure-
check
2
Warning: Petrol is extremely
flammable, so take extra
precautions when you work on
any part of the fuel system. See
the Warning in Section 2.
Note: To perform the fuel pressure test, you
will need to obtain a fuel pressure gauge and
adapter set (fuel line fittings).
Note: On 1988 to 1990 models, the fuel pump
may chatter excessively and the engine may
stall frequently during hot weather. If stalling
occurs, the engine will restart after a cool-
down period. Dual fuel pumps can be installed
by a dealer service department or other
qualified repair facility to remedy this problem.
Preliminary inspection
1Should the fuel system fail to deliver the
proper amount of fuel, or any fuel at all,
inspect it as follows. Remove the fuel filler
cap. Have an assistant turn the ignition key to
the ON position (engine not running) while you
listen at the fuel filler opening. You should
hear a whirring sound that lasts for a couple of
seconds. On 1988 to 1990 models, listen
behind the left rear wheel (external fuel pump)
for the fuel pump sound.
2If you don’t hear anything, check the fuel
pump relay (see illustration 2.3a, b or c)and
4•2 Fuel and exhaust systems
2.3c On 1992 models, the fuel pump relay
is located in the left rear corner of the
engine compartment
3261 Jaguar XJ6 2.3a Relay locations on a 1988 model
2.3b Relay locations on a 1989 model

of these sensors and their corresponding
ECU-controlled relays are not contained
within EFI components, but are located
throughout the engine compartment. For
further information regarding the ECU and its
relationship to the engine electrical and
ignition system, see Chapter 6.
12 Electronic Fuel Injection
(EFI) system- check
2
1Check the earth wire connections for
tightness. Check all wiring and electrical
connectors that are related to the system.
Loose electrical connectors and poor grounds
can cause many problems that resemble
more serious malfunctions.
2Check to see that the battery is fully
charged, as the control unit and sensors
depend on an accurate supply voltage in
order to properly meter the fuel.
3Check the air filter element - a dirty or
partially blocked filter will severely impede
performance and economy (see Chapter 1).
4If a blown fuse is found, renew it and see if
it blows again. If it does, search for a shorted
wire in the harness related to the system.
5Check the air intake duct from the MAF
sensor to the intake manifold for leaks, which
will result in an excessively lean mixture. Also
check the condition of the vacuum hoses
connected to the intake manifold.
6Remove the air intake duct from the throttle
body and check for carbon and residue build-
up. If it’s dirty, clean with aerosol carburettor
cleaner (make sure the can says it’s safe for
use with oxygen sensors and catalytic
converters) and a toothbrush.
7With the engine running, place a
stethoscope against each injector, one at a
time, and listen for a clicking sound, indicating
operation (see illustration).8If there is a problem with an injector,
purchase a special injector test light (noid
light) and refit it into the injector electrical
connector (see illustration). Start the engine
and make sure that each injector connector
flashes the noid light. This will test for the
proper voltage signal to the injector.Caution:
If the engine will not start and the noid
light indicates that each injector is
receiving the proper signal, there is a good
possibility that the injector(s) is stuck open
and allowing fuel into the combustion
chamber in excessive amounts. If the spark
plugs are fouled, detach the primary (low
voltage) wires from the ignition coil, disable
the fuel pump by removing the fuel pump
relay (see Section 2), remove the spark plugs
and crank the engine over. If fuel sprays from
the spark plug holes, the engine is flooded
and the fuel must be removed from the
combustion chambers.
9With the engine OFF and the fuel injector
electrical connectors disconnected, measure
the resistance of each injector (see
illustration). Each injector should measure
about 2.0 to 3.0 ohms. If not, the injector is
probably faulty.10The remainder of the system checks
should be left to a Jaguar service department
or other qualified repair workshop, as there is
a chance that the control unit may be
damaged if not performed properly.
13 Electronic Fuel Injection
(EFI) system- component
check and renewal
3
Warning: Petrol is extremely
flammable, so take extra
precautions when you work on
any part of the fuel system. See
the Warning in Section 2.
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.
Throttle body
Check
1Verify that the throttle linkage operates
smoothly.
2Start the engine, detach each vacuum hose
and, using your finger, check the vacuum at
each port on the throttle body with the engine
at idle and above idle. The vacuum available
from the throttle body is ported. Raise the
engine rpm and watch as vacuum increases.
It may be necessary to use a vacuum gauge.
Refer to Chapter 2B for additional information
concerning vacuum checks.
Renewal
Warning: Wait until the engine is
completely cool before
beginning this procedure.
3Detach the cable from the negative terminal
of the battery (see the Cautionat the
beginning of this Section).
4Drain the radiator (see Chapter 1).
4•10 Fuel and exhaust systems
12.9 Using an ohmmeter, measure the
resistance across both terminals
of the injector
3261 Jaguar XJ6 12.7 Use a stethoscope or a screwdriver to determine if the
injectors are working properly - they should make a steady
clicking sound that rises and falls with engine speed changes
12.8 Refit the “noid” light into the fuel injector electrical
connector and check to see that it blinks with the engine running

headlights or heated rear window and confirm
that the engine rpm decreases at first and
then increases. This check monitors the ISC
motor as it is signalled by the computer to
increase idle speed due to additional
amperage required from the charging system.
As the headlights draw current from the
charging system, the alternator will create
resistance on the belt as it works to produce
the additional energy. If the rpm does not
increase, check the ISC motor.
23Check for approximately 11.2 volts to the
ISC stepper motor (see illustrations).
Disconnect the ISC harness connector and
working on the harness side, check for
11.2 volts with the ignition key ON (engine not
running). Also, check the corresponding
terminals for the correct voltage amounts. If
the correct voltage does not exist, check the
wiring harness. Refer to the wiring diagrams
at the end of Chapter 12.24The ISC motor or stepper motor can be
checked for correct operation but a special tool
is required to activate the internal coils. Have
the stepper motor checked by a dealer service
department or other qualified repair workshop.
25Reconnect the ISC motor electrical
connector.
Renewal
26Detach the cable from the negative
terminal of the battery (see Cautionat the
beginning of this Section).
27Use a large open-end spanner and
unscrew the ISC motor from the housing (see
illustration).
28Refitting is the reverse of removal, but be
sure to use a new gasket.
Fuel rail and fuel injectors
Note:If there is a distinct knocking noise
coming from the dash when the engine is
idling, the fuel feed hose may have hardenedrestricting fuel flow and causing abnormal
sounds. Replace the fuel inlet (feed) hose with
a new part from the dealer parts department.
Check
29Refer to the fuel injection system checking
procedure (see Section 12).
Renewal
30Relieve the fuel pressure (see Section 2).
31Detach the cable from the negative
terminal of the battery (see Cautionat the
beginning of this Section).
32Disconnect the fuel injector wiring con-
nectors and set the injector wire harness aside.
33Detach the vacuum sensing hose from the
fuel pressure regulator.
34Disconnect the fuel lines from the fuel
pressure regulator and the fuel rail (see
illustration 3.6a)
35Remove the fuel rail mounting bolts (see
illustration).
4•12 Fuel and exhaust systems
3261 Jaguar XJ6 13.23a To check the ISC motor, turn the ignition key ON
(engine not running) and check for the proper voltage amounts
at the harness connector (1989 model shown)
13.23b Later models are equipped with a different shape
ISC connector but the voltage values should be the same
as the early style
13.27 Use a large open end spanner to remove the ISC motor
from the intake manifold13.35 Remove the fuel rail mounting bolts (arrowed) . . .

36Remove the fuel rail with the fuel injectors
attached (see illustration).
37Prise off the clips and remove the fuel
injector(s) from the fuel rail (see illustration).
38If you are replacing the injector(s), discard
the old injector. If you intend to re-use the
same injectors, renew the grommets and
O-rings (see illustrations).
39Refitting of the fuel injectors is the reverse
of removal. Apply a light film of clean engine
oil to the O-rings before refitting them.
40Tighten the fuel rail mounting bolts to the
torque listed in this Chapter’s Specifications.
Fuel pressure regulator
Check
41Refer to the fuel pump/fuel pressure
check procedure (see Section 3).
Renewal
42Relieve the fuel pressure (see Section 2)
and detach the cable from the negative
terminal of the battery (see the Cautionat the
beginning of this Section).
43Detach the vacuum hose from the
regulator.
44Remove the fuel rail and the injectors as
an assembly (see Steps 30 to 39).
45Remove the fuel line from the fuel
pressure regulator (see illustration).
46Remove the fuel pressure regulator
mounting bolts and detach the pressure
regulator from the engine.
47The remainder of refitting is the reverse of
removal. Make sure the fuel lines are secure
and there are no leaks before using the car.
Supplementary air valve
Check
48The supplementary air valve provides
additional throttle valve bypass air during cold
starting and cold running conditions below
15° F. This output actuator is controlled by the
computer (ECU) in response to informationreceived from the coolant temperature sensor,
intake air temperature sensor and other
information sensors working with the fuel
injection system.
49Check for battery voltage to the
supplementary air valve. With the engine cold,
backprobe the electrical connector using a
long pin and check for battery voltage (see
illustration). Voltage should exist.
50Because of the special tools required to
test the supplementary air valve, have it
tested by a dealer service department or other
qualified repair facility.
Renewal
51Remove the intake hoses, the mounting
screws and detach the supplementary air
valve from the engine.
52Refitting is the reverse of removal.
53Be sure to use a new gasket when refitting
the idle-up valve.
Air intake plenum
Note:The air intake plenum is removed and
installed as a complete unit with the intake
manifold. In the event of damage or leaks,
remove the air intake plenum and intake
Fuel and exhaust systems 4•13
4
3261 Jaguar XJ6 13.36 . . . and remove the fuel rail with the fuel injectors attached
13.37 Remove the fuel injector retaining clips from the fuel rail
using a small screwdriver
13.45 Disconnect the fuel pressure
regulator from the fuel return line
13.38b Pick out the old injector seal but
make sure the injector body is not
damaged in the process13.38a If you plan to refit the original
injectors, remove and discard the O-rings
and grommets and fit new ones
13.49 Check for battery voltage to the
supplementary air valve