1998 JAGUAR X308 egr

Engine System - General Infor
mation - Engine
Description an
d Operation

The AJ26 power unit is available in 3.2 L and 4.0 L versions, and comprises:
An eight cylinder 9
0 degree 'V' config
uration liquid cooled aluminium cylinder block incorporating 'Nikasil' plated
cylinder bores.
Pi
stons of open-ended skirt design, with
two compression and one oil control ring.
Two al
uminium cylinder heads, each
incorporating two camshafts.
F
our valves per cylinder.
Al

uminium valve lifters and top mounted shims.
Vari

able valve timing (VVT) of the inlet camshafts (4.0 L normally aspirated only).
Camshaft

covers manufactured from Vinylester.
Al

uminium timing cover which accommodat
es the crankshaft front oil seal.
Sin
gle row primary and secondary chains dr
ive the camshafts of each cylinder bank.
An alu
minium bed pl
ate, incorporating iron main bearing supports, which accomm odate the oil pump pick-up,

Speed an
d load
Coo
l
ant temperature
Ti
me el
apsed from start up
Cl
osed l
oop fuelling
Determination of the vapour concentration is made by stepped opening of the EVAP valve and subsequent monitoring of the
fuelling correction. This function is performed prior to purging, so that at the onse t of purging the EVAP valve can be set to
the optimum position. Should the ECM be unable to determine the concentration before purging, a default value is
employed, which is then modified whilst purging is in progress.
When the purging process is operational th e ECM modifies the basic fuelling calculation to maintain the correct air / fuel
ratio.
Purging is inhibited during fuel cut-off and stability / traction control intervention.
Coolant Temperature Sen
sor
Th
e
sensor outputs a voltage to the ECM which decreases as temperature increases.
Cooling Fans


In response to engi
ne coolant temperat
u
re and climate control system demand, the ECM will energize the cooling fans.
Climate Control Compressor
The E
C
M will allow the compressor clutch to be engaged if th
e engine temperature and load demand are normal. Should the
driver require maximum engine powe r or the coolant temperature be high, the request will be denied.
Cranking Signal

The ECM reacts to a signal fr
om th
e Body Processor Module (BPM) when the starter motor relay is energi
zed. This signal is
used to trigger starting, fu el and ignition strategies.
Engine Speed and Cranksh
aft Position
Engine
speed and cran
k position are moni
tored by a sensor which is mounted on the cylinder block (flywheel housing)
behind the crankshaft drive plat e. It indicates rotational speed to the ECM in the form of 12 pulses per crank revolution.
Engine speed is used for synchronization of fuel an d ignition systems, as well as other functions.
Camshaft Position
The ca
mshaft position sensor is mounted at
the rear of Bank 2 cylinder head on the inlet side and provides one signal every
720 degrees of crankshaft rotation. The signal, in conjunction with the signal from the crankshaft position sensor, indicates
to the ECM that the piston of cylinder 1A is approaching TDC on the compression stroke.
Variable Valve
Timing (Where Fitted)
By energi
si
ng a solenoid to allow the pass
age of pressurized oil on each of the inle t camshaft drives, the ECM can vary by a
single stepped amount, the relati ve timing of the inlet valves.
Ign
ition
Ignit
i
on spark is produced by
individual on-plug coil units.
There are two ignition amplifiers; module #1 drives coils 1A, 2B, 3B and 4A, whilst module #2 drives coils 1B, 2A, 3A and
4B. The ECM controls the amplifiers.

Thi
s sensor uses a piezo-electric sensing element to detect kn
ock which may occur under acceleration at critical conditions.
Should detonation be present the ECM will retard ignition timing of individual cylinders.
Exhaust G
as Recirculation
The EGR
valve (where fitted) reduces NOx
emissions by recirculating a portion of the exhaust gases back into the inlet
manifold.
Heated Oxyg
en Sensors
The h
eated oxygen sensors, one per bank, are situated upstream of the catalysts. Integral
to the sensors are heaters
(under ECM control) which allow the sensor s to reach their operating temperature as soon as possible after engine start. A
comparison between the level of oxygen in the exhaust gas to that in the atmosphere produces an output signal. This signal
is used by the engine closed loop fuel strategy to make fuelling corrections and so control overall emission levels.
Oxygen Sensors

Thes
e sensors, one per bank, are situated downstream of the
catalyst. The comparison of upstream and downstream signals
allows determination of cata lyst conversion efficiency.




Knock Sensor

Engine - Exhaust Manifold RH
In-vehicle Repair
Removal
1. Open the engine compartment and fit paintwork protection
sheets.
2. Remove the air cleaner assemb ly. Refer to Section 303-12.
3. Remove the front silencer. Refer to Section 309-00.
4. Remove the downpipe catalytic converter, right hand side.
Refer to Section 309-00.

5. From above the vehicle, disconnect the EGR pipe from the
exhaust manifold.
1. Remove the two nuts whic h secure the EGR flange to
the right hand exhaust manifold.
2. Reposition the EGR pipe from the manifold.

6. Remove the bolts which secure th e front section of the exhaust
manifold to the cylinder head.

7. If working on a right hand drive vehicle; reposition the steering rack for access.
1. Remove the two bolts which secure the steering rack at the passenger side.
2. Loosen, but do not remove, the two bolts which secure the steering rack at the driver's side.
Reposition the steering rack for access.
8. Working from below the vehicle, remove the manifold bolts.
1. Remove the bolts which secu re the rear section of the
exhaust manifold to the cylinder head.

Installation


9. Remove the manifold.
1. Remove the manifold and the manifold gasket from the cylinder head.
2. Remove the gasket from the EGR flange.
10. If fitting a new manifold, remove the two studs from the EGR
flange of the manifold. and transfer them to the new manifold.
11. Clean the manifold faces (if refi tting) and the mating faces on
the cylinder head.
12. Use a thread tap (plug) to clean out the threads of the
manifold securing bolt holes, in the cylinder head.
1. Fit a spacer to each new manifo ld securing bolt (8 bolts).

2. Fit the manifold and manifold gasket.
1. Fit and align the new gasket to the cylinder head.
2. Fit and align the manifo ld to the cylinder head.
3. Fit the rear four bolts wh ich secure the manifold, but
do not tighten.
3. Working from above the vehicle, fit and tighten the remaining
manifold securing bolts.
4. Working from below the vehicle, fu lly tighten the rear bolts on
each manifold.
5. Refit the steering rack (if removed for access).
1. Reposition th e steering rack.
2. Fit and tighten the rack mounting bolts on the passenger side.

3. Tighten the rack mounting bolts on the driver's side.

6. From above the vehicle, connect the EGR pipe to the exhaust
manifold.
1. Fit a new EGR gasket to the manifold.
2. Reposition the EGR pipe to the manifold.
3. Fit the two nuts which secure the EGR flange to the exhaust manifold.
7. Fit the downpipe catalytic converter, right hand side. Refer to
Section 309-00.
8. Fit the front silencer. Refer to Section 309-00.
9. Fit the air cleaner assembly . Refer to Section 303-12.
10. Remove paintwork protection sheets and close the engine
compartment.

Engine - Exhaust Manifold LH and RH
In-vehicle Repair
Removal
1. Open the engine compartment and fit paintwork protection
sheets.
2. Remove the downpipe catalytic converter, right hand side.
Refer to Section 309-00.
3. Remove the downpipe catalytic co nverter, left hand side. Refer
to Section 309-00.
4. Remove the front silencer. Refer to Section 309-00.
5. Remove the air cleaner assemb ly. Refer to Section 303-12.

6. Working from above the vehicl e, remove the bolts which
secure the front sectio n of the left hand exhaust manifold to
the cylinder head.

7. Working from below the vehicle, reposition the steering rack
for access.
1. Remove the two bolts which secure the steering rack at the driver's side.
2. Loosen, but do not remove, the two bolts which secure the steering rack at the passenger side.
Reposition the steering rack for access.

8. Working from below the vehicl e, remove the manifold.
1. Remove the bolts which secu re the rear section of the
exhaust manifold to the cylinder head.
2. Remove the manifold and the manifold gasket.
9. From above the vehicle, disconnect the EGR pipe from the
right hand exhaust manifold.
1. Remove the two nuts whic h secure the EGR flange to
the right hand exhaust manifold.
2. Reposition the EGR pipe from the manifold.

10. Remove the bolts which secure the front section of the right
hand exhaust manifold to the cylinder head.

11. Working from below the vehicle, remove the manifold bolts.
1. Remove the bolts which secu re the rear section of the
exhaust manifold to the cylinder head.

12. Remove the manifold.
1. Remove the manifold and the manifold gasket from the cylinder head.
2. Remove the gasket from the EGR flange.
13. If fitting a new manifold, remove the two studs from the EGR
flange of the manifold. and transfer them to the new manifold.
14. Clean the manifold faces (if refitting), the EGR pipe flange
and the mating faces on the cylinder head.
15. Use a thread tap (M8 x 1,25 plug) to clean out the threads of
each manifold securing bolt hole, in the cylinder heads.