1999 JAGUAR S TYPE light

IntroductionAJ-V6/AJ28
3 The new S-TYPE sports sedan has an in-line powertrain and rear wheel drive configuration and is
available with either a 3 Litre V6 or a 4 Litre V8 engine, both normally aspirated. The V6 engine,
designated AJ-V6 is new to the Jaguar range and provides expected Jaguar levels of performance with
smooth power delivery, economy and excellent torque characteristics across the engine speed/load
range. The engine is of a lightweight but rigid design with particular attention paid to minimising noise
and vibration. A major innovation is the use of a variable geometry air intake manifold, which is
controlled, via valves, by the engine management system and produces optimised volumetric efficiency
at all engine speeds. Two stage variable valve timing is also fitted and both systems are optimised
together to achieve the wide torque delivery at all engine speeds.
The V8 engine, designated AJ28, is a developement of the now established engine fitted to the
successfull XK Series sports and XJ Series sedan and incorporates the latest modifications fitted to the
AJ27 variant, in particular the continuously variable valve timing system and air assisted fuel injection.
Both the V6 and V8 engines are fitted with a new, common, electronic throttle which does not require a
mechanical cable. Another new feature, also common to both engines, is the use of a returnless fuel
system to reduce the formation of fuel vapour (evaporative emissions).
A new 5-speed automatic transmission is fitted (with slight differences) to both engines. In certain
markets only, an optional 5-speed manual transmission, with new self-adjusting clutch, is available for
the V6 engine only.
Both engines and the automatic transmission are controlled by a completely new powertrain control
system.

4
Introduction
D.303.1201
AJ-V6 ENGINEThe AJ-V6 is a water cooled six cylinder engine
configured as two banks of cylinders in a 60û V
formation. Valve operation is via chain driven
double overhead camshafts on each cylinder
bank. The engine is naturally aspirated but with a
unique air intake system which significantly
improves power output. Lightweight materials are
used extensively but the structural design is such
as to maintain a strong rigid assembly.The main features of the power unit are:
¥ three stage variable geometry intake manifold
¥ electronic throttle with cable-less operation
¥ two position variable valve timing
¥ returnless fuel system
¥ fail safe cooling system
V6 Engine
D.303.1202D.303.1201 &1202
AJ-V6/AJ28

V6 Engine
8
Cylinder Head
The aluminium alloy cylinder heads have square
squish combustion chambers with four valve
ports and a central spark plug. Each head is
aligned to the cylinder block via two split hollow
dowels and sealed with a composite stainless steel
gasket. Steel balls (10.11mm diameter) are used
to plug the external bores of the oilway drillings
and cup plugs are fitted to the water jacket
openings. Two half round aluminium cap inserts
are fitted via a sealant at the rear of the head.
Cam Cover
The cylinder heads are fitted with lightweight
polyester cam covers, (bank 2 is silver colored)
with silicone seals, to save weight and reduce
airborne noise. A central aperture allows access to
the coil on plug units and a second hole has a
grommet through which the VVT oil control valve
protrudes. The oil filler hole is in the LH cover.
D.303.1368
CYLINDER HEAD
D.303.1207
CAM COVER
D.303.1207
Cylinder Head Assembly
D.303.1368
AJ-V6/AJ28

V6 EngineAJ-V6/AJ28
9
Camshafts and Valve Gear
The basic camshaft consists of individual
machined cam lobes, thrust washer and end plug
assembled on a steel tube. The exhaust camshafts
also have a pressed on drive sprocket, forming a
single camshaft assembly. On the inlet camshaft
the drive sprocket is fixed to the VVT unit which
is removable but the rear end of the camshaft is
fitted with a pressed on multi-tooth sensor ring.
Each camshaft is supported in four bearings with
the front (thrust) bearing cap having a special
oilway for the VVT unit (see VVT section): on the
exhaust camshaft this oilway is redundant. The
bearing caps are made of aluminium.
The cams actuate the valves via direct acting
mechanical bucket tappets made of lightweight
aluminium with phosphate coated cast iron shims
D.303.1209
CAMSHAFTS AND VALVE GEAR
D.303.1209
mounted on top. The valve components are of
lightweight design with 5.5mm valve stems.
VVT Unit
Inlet Camshaft
Exhaust Camshaft

V6 EngineAJ-V6/AJ28
15
Oil Cooler and Filter Mounting
The oil filter and oil cooler are mounted slightly
away from the cylinder block on an aluminium
alloy adaptor which is an integral extension of the
LH engine mount. The oil filter is a replaceable
canister screw on type and the cooler is fixed by a
single through bolt to the adaptor. Both
components are connected to the cylinder block
through internal oilways in the adaptor casting
and via an interfacing filter mounting in the
block. A hollow bolt passes through the
adaptor/engine mount and screws into the centre
channel of the block filter mounting to provide
the oil return from the cooler to the cylinder
block.
The adaptor mounted oil cooler is an oil to water
heat exchanger and the coolant matrix is
connected via hoses into the main coolant system
at the radiator bottom hose (see Cooling System).
ENGINE OIL PRESSURE AND OIL TEMPERATURE SENSORS
D.303.1205
OIL COOLER AND FILTER ASSEMBLY
EOP Sensor
EOT Sensor
D.303.1205
D.303.1371
Engine Oil Pressure (EOP) and Oil
Temperature (EOT) Sensors
EOP and EOT sensors are fitted on the LH side of
the cylinder block in the return feed from the oil
cooler. The oil temperature is monitored to
provide data for the VVT system.
Oil Cooler
Hollow Bolt
Engine Mount/
Oil Cooler Adapter

V6 Engine AJ-V6/AJ28
28¥ Limp home mode in which a high idle speed
is set, with no accelerator pedal response, to
allow the vehicle to creep: the RED warning
light and FAIL SAFE ENGINE MODE message
are activated: this mode is set by, eg the loss
of two or more sensors.
¥ Engine shutdown due to serious throttle
malfunction.
J.303.1363
THROTTLE CONTROL SYSTEM
System Monitoring
Within the PCM, operation of the overall throttle
control system (main processor logic and
software) is itself monitored by a separate,
independent microprocessor, the electronic
throttle monitor. Communication is maintained
between the two processors but if it is lost or if
faults are detected by the monitor (eg throttle
angle greater than demanded), the monitor
processor may call for a restricted operating mode
such as cruise cancellation or a forced idle
condition or engine shutdown.
Failure Modes
There are four failure modes:
¥ Loss of redundancy eg a failure of one sensor
output: this type of fault causes the AMBER
warning light to illuminate and FAIL SAFE
ENGINE MODE to be displayed on the
message centre (the engine remains fully
functional).
¥ Cruise inhibit.
J.303.1363
PCM
Electronic
Throttle
Monitor
Main
Processor
SystemTAC
Module
Motor
Electronic Throttle
TP Sensor
Command 1
Command 2
SCP
APP
Sensor
Motor Winding 1
Motor Winding 2
To the TP Sensor
APP1
APP2
APP3
5V
5V
5V
5V
5V
12V
12V
TP1
TP2
TP3
Inductive
Position
Encoder

V6 EngineAJ-V6/AJ28
29
D.303.1215
FUEL RAIL AND LOWER INTAKE MANIFOLD
Fuel Supply
D.303.1215
EFT Sensor
De-pressurisation
Valve
IP Sensor
Fuel System
Returnless Fuel System
The returnless fuel system is a one way system
which delivers fuel to the engine without the
requirement for fuel to be returned to the tank.
When a return line is used, the effects of fuel
pressurisation, de-pressurisation and engine heat
on the returning fuel causes extra vapour to be
generated in the tank. With increasing regulatory
controls on evaporative emissions, this is an
undesirable condition and elimination of a fuel
return line provides significant benefits.
The in-tank fuel pump supplies fuel and regulates
pressure to the injectors under control of the PCM
and the rear electronic module (REM) and a
pressure regulator is not therefore required on the
engine fuel rail. To provide feedback for closed
loop control, an injector pressure (IP) sensor on
the fuel rail detects the pressure differentialbetween the fuel and the intake manifold and the
engine fuel temperature (EFT) sensor monitors
fuel temperature. Analogue signals from both
sensors are sent to the PCM to indicate the
pressure of the fuel and to detect whether it has
reached the vapourisation point. In response to
the sensor inputs and driver or load demands, the
PCM requests the pump system to vary the fuel
flow; in particular, fuel pressure will always be
increased to avoid vapour formation and to
maintain flow through the injectors.
Fuel pump control is further described in the
ÔS-TYPE IntroductionÕ Technical Guide.
Fuel Rail and Lower Intake Manifold
The fuel injectors are seated in two lower intake
manifolds, made of a lightweight plastic
composite material, which are fitted between the
Fuel Rail
Lower Intake
Manifold

V6 Engine AJ-V6/AJ28
36
Fail Safe Cooling System
A unique feature of the V6 engine is the use of a fail safe cooling strategy, controlled by the EMS, in the
event of coolant loss leading to rising engine temperatures. The principle of the strategy involves
switching off one or more fuel injectors to inhibit combustion and reduce heat, thus allowing the flow of
ambient intake air to further cool the selected cylinders. By cycling the selected cylinders, ie switching
different injectors off for a period and in a sequence determined by EMS parameters, overall engine
temperature can be controlled sufficiently to allow the vehicle to be driven, at reduced power, for a
short distance. Throughout the malfunction period, instrument panel messages and warnings advise the
driver of the current status of the cooling system as described below.
Driver Indication and EMS Action
The fail safe strategy moves though different stages depending on engine temperature:
¥ Temperatures below 122û C (250û F) are within the normal range. At high temperatures below this
level the temperature gauge pointer enters the red zone.
¥ If the temperature rises to between 122û C - 127û C (250û F to 260û F) no action is taken by the EMS
which affects engine running but the following indications appear:
Temperature gauge pointer in red zone
Message Centre HIGH ENGINE TEMPERATURE
Warning light TEMP
Priority light red
Audible indicator single chime sounded
¥ If the temperature rises to 127û C (260û F) or above, the fail safe strategy operates. At 127û C (260û F),
the EMS will cut out one cylinder (the selected cylinder is varied) and as the temperature continues
to rise, this will increase to a maximum of three cylinders cut (with cylinder cycling). The following
indications are given:
Temperature gauge pointer in red zone
Message Centre ENGINE POWER REDUCED
Warning light TEMP
Priority light red
Audible indicator three chimes sounded
¥ At 166û C (300û F) or above, the fail safe strategy continues as described but the following
indications are given:
Temperature gauge pointer in red zone
Message Centre PULL OFF ROAD SAFELY alternates with TURN OFF IGNITION
Warning light TEMP flashes
Priority light red
Audible indicator five chimes sounded
¥ EMS shuts the engine down.