1999 LAND ROVER DISCOVERY spark plugs

ENGINE - V8
12-2-18 REPAIRS
13.Remove cylinder head gasket.
Refit
1.Clean mating faces of cylinder block and head
using suitable gasket removal spray and a
plastic scraper, ensure that bolt holes in block
are clean and dry. Clean mating faces of
cylinder head and exhaust manifold.
CAUTION: Do not use a metal scraper or
machined surfaces may be damaged.
2.Check head and block faces for warping and
pitting. If out of specification, renew head.
3. Models with SAI: Using a 5/8 in x 20 TPI
(threads per inch) UNF tap having a class 2A
thread, remove deposits from secondary air
injection adapter tappings in cylinder head.
CAUTION: Ensure that tap used has 20 TPI.
4.Fit cylinder head gasket with the word 'TOP'
uppermost.
CAUTION: Gasket must be fitted dry.
5.Carefully fit cylinder head and locate on
dowels.
6.Lightly lubricate new cylinder head bolt threads
with clean engine oil. 7.Noting that bolts 1, 3 and 5 are longer than the
remainder, fit bolts and tighten in the sequence
shown to 20 Nm (15 lbf.ft) then 90°, and finally
a further 90°.
CAUTION: Do not tighten bolts 180° in one
operation.
8. Models with SAI: Fit new air injection adapters
and using a 9 mm hexagonal drive bit, tighten
to 33 Nm (24 lbf.ft).
CAUTION: Do not use an air tool to tighten
adapters.
9.Clean push rods.
10.Lubricate ends of push rods with clean engine
oil.
11.Fit push rods in their removed order.
12.Clean bases of rocker pillars and mating faces
on cylinder head.
13.Clean contact surfaces on rockers, valves and
push rods.
14.Lubricate contact surfaces and rocker shaft
with clean engine oil.
15.Fit rocker shaft assembly and engage push
rods.
16.Fit rocker shaft bolts and progressively tighten
to 40 Nm (30 lbf.ft).
17.Position alternator mounting bracket, fit bolts
and tighten to 40 Nm (30 lbf.ft).
18.Position auxiliary drive belt tensioner, fit bolt
and tighten to 45 Nm (33 lbf.ft).
19.Connect ht leads to spark plugs in their fitted
order.
20. Using new gaskets, fit exhaust manifold to
cylinder head. Fit bolts and using sequence
shown, tighten initially to 15 Nm (11 lbf.ft), then
finally tighten to 36 Nm (28 lbf.ft).
21. RH drive models: Fit brake servo heat shield.

+ MANIFOLDS AND EXHAUST
SYSTEMS - V8, REPAIRS, Heat shield -
brake servo - Without Secondary Air
Injection.
22.Position engine earth lead, fit bolt and tighten to
22 Nm (16 lbf.ft).
23.Fit inlet manifold gasket.

+ MANIFOLDS AND EXHAUST
SYSTEMS - V8, REPAIRS, Gasket - inlet
manifold - lower.

ENGINE - V8
12-2-48 OVERHAUL
21.Position alternator cables and tighten terminal
B+ to 18 Nm (13 lbf.ft) and terminal D+ to 5 Nm
(3.5 lbf.ft).
22.Position auxiliary housing, fit bolts and tighten
to 40 Nm (30 lbf.ft). Fit nut and tighten to 22 Nm
(17 lbf.ft).
23.Clean jockey pulley mating faces.
24.Position jockey pulley and tighten bolt to 50 Nm
(37 lbf.ft).
25.Clean PAS pump pulley mating faces.
26.Position PAS pump pulley, fit bolts and tighten
to 22 Nm (17 lbf.ft).
27.Secure injector harness and connect injector
multiplugs.
28.Connect multiplug to coolant thermistor.
Gasket - exhaust manifold
$% 30.15.12.01
Disassembly
1.Remove 8 bolts securing exhaust manifold and
collect spacers. Discard the bolts.
2.Remove exhaust manifold.
3.Remove 2 manifold gaskets and discard.
Reassembly
1.Clean exhaust manifold and cylinder head
mating face.
CAUTION: Do not use a metal scraper or
machined surfaces may be damaged.
2.Fit new gaskets, dry, fit exhaust manifold.
CAUTION: Ensure that link bar on gasket is
positioned below spark plugs.
LH bank illustrated
3.Fit spacers to new manifold bolts and, working
in the sequence illustrated, initially tighten bolts
to 15 Nm (11 lbf.ft), then finally tighten to 38 Nm
(28 lbf.ft).

ENGINE - V8
OVERHAUL 12-2-61
Gasket - cylinder head
$% 12.29.02.01
Disassembly
1.Remove inlet manifold gasket.

+ ENGINE - V8, OVERHAUL, Gasket -
inlet manifold.
2. RH cylinder head: Remove auxiliary drive belt
tensioner.
3. RH cylinder head: Remove bolts securing
alternator mounting bracket and remove
bracket.
4.Noting their fitted order, disconnect ht leads
from spark plugs.
5.Progressively remove 4 bolts securing the
rocker shaft and remove rocker shaft.
6.Remove push rods and store in their fitted
order. 7. Models with SAI: Using a 9 mm hexagonal
drive bit, remove 2 air injection adapters from
cylinder head; discard adapters.
To release the adapter thread locking agent
and prevent damage to the cylinder head,
remove the adapters by alternately loosening
then tightening slightly. Repeat this procedure
until adapters are removed.
CAUTION: Do not use air tools to remove
adapters.
8.Working in the sequence shown remove 10
bolts securing the cylinder head to block.
Discard the bolts.
9.Remove cylinder head.

ENGINE - V8
12-2-62 OVERHAUL
10.Remove cylinder head gasket.
CAUTION: Support both ends of cylinder
head on blocks of wood.
Inspect
1.Clean mating faces of cylinder block and head
using suitable gasket removal spray and a
plastic scraper, ensure that bolt holes in block
are clean and dry.
CAUTION: Do not use a metal scraper or
machined surfaces may be damaged.
2.Check head and block faces for warping and
pitting.
lMaximum cylinder head warp = 0.05 mm
(0.002 in).
Note: Cylinder head can be refaced to 0.50
mm (0.02 in) maximum below head height –
See cylinder head overhaul.
3. Models with SAI: Using a 5/8 in x 20 TPI (
threads per inch) UNF tap having a class 2A
thread, remove deposits from secondary air
injection adapter tappings in cylinder head.
CAUTION: Ensure that tap used has 20 TPI.Reassembly
1.Ensure that cylinder head bolt holes are clean
and dry.
2.Fit cylinder head gasket with the word TOP
uppermost.
CAUTION: Gaskets must be fitted dry.
3.Carefully fit cylinder head and locate on
dowels.
4.Lightly lubricate new cylinder head bolt threads
with clean engine oil.
5.Noting that bolts 1, 3 and 5 are longer than the
remainder, fit bolts and tighten in the sequence
shown to 20 Nm (15 lbf.ft) then turn through 90
°, then a further 90 °. CAUTION: Do not
tighten bolts 180° in one operation.
6. Models with SAI: Fit new air injection adapters
and using a 9 mm hexagonal drive bit, tighten
to 33 Nm (24 lbf.ft).
CAUTION: Do not use an air tool to tighten
adapters.
7.Clean the push rods, Lubricate ends of push
rods with clean engine oil, and fit in their
removed order.
8.Clean bases of rocker pillars and mating faces
on cylinder head.
9.Clean contact surfaces on rockers, valves and
push rods.
10.Lubricate contact surfaces and rocker shaft
with clean engine oil.
11.Fit rocker shaft assembly and engage push
rods.
12.Fit rocker shaft bolts and progressively tighten
to 40 Nm (30 lbf.ft).
13.Connect ht leads to spark plugs in their correct
fitted order.
14. RH cylinder head: Position alternator
mounting bracket, fit bolts and tighten to 40 Nm
(30 lbf.ft).
15. RH cylinder head: Fit auxiliary drive belt
tensioner.
16.Fit inlet manifold gasket.

+ ENGINE - V8, OVERHAUL, Gasket -
inlet manifold.

ENGINE MANAGEMENT SYSTEM - V8
DESCRIPTION AND OPERATION 18-2-3
1Mass air flow/ inlet air temperature sensor
2Fuel injectors
3High tension leads/spark plugs
4Fuel pump relay
5ATC compressor clutch relay/ cooling fan relay
6Throttle position sensor
7Heated oxygen sensor
8Idle air control valve
9Ignition coils
10Engine coolant temperature sensor
11Crankshaft speed and position sensor
12Knock sensor
13Camshaft position sensor

ENGINE MANAGEMENT SYSTEM - V8
DESCRIPTION AND OPERATION 18-2-5
1Engine control module
2Crankshaft speed and position sensor
3Camshaft position sensor
4Engine coolant temperature sensor
5Mass air flow/ inlet air temperature sensor
6Throttle position sensor
7Heated oxygen sensors
8Fuel injectors
9Idle air control valve
10Fuel pump relay
11EVAP canister
12EVAP canister vent valve
13EVAP canister purge valve
14Fuel tank pressure sensor15Ignition coils
16Knock sensor
17Spark plugs
18High/ Low ratio switch
19Malfunction indication lamp
20Diagnostic connector
21Air temperature control clutch relay
22Air temperature control cooling fan relay
23ATC ECU
24CAN link to EAT
25SLABS ECU
26BCU
27Instrument cluster
28Thermostat monitoring sensor (where fitted)

ENGINE MANAGEMENT SYSTEM - V8
DESCRIPTION AND OPERATION 18-2-7
The ECM controls the following outputs:
lFuel injectors (1 per cylinder).
lIgnition coils/ high tension leads/ spark plugs.
lFuel pump relay.
lIdle air control valve.
lHeated oxygen sensors.
lEVAP canister purge valve.
lEVAP canister vent solenoid (CVS) valve (where fitted).
lMalfunction Indicator Lamp (MIL)/ service engine soon lamp (where fitted).
lHill descent control (via SLABS interface).
lEVAP system fuel leak detection pump (where fitted)
lSecondary air injection pump (where fitted)
The ECM also interfaces with the following:
lDiagnostics via diagnostic connector with TestBook.
lController Area Network (CAN) link to EAT ECU.
lAir conditioning system.
lSelf Levelling & Anti-lock Braking System (SLABS) ECU.
lImmobilisation system via the body control unit (BCU).
lInstrument cluster.
lCruise control ECU
lActive Cornering Enhancement (ACE) ECU

ENGINE MANAGEMENT SYSTEM - V8
DESCRIPTION AND OPERATION 18-2-43
The ECM performs the following diagnostic checks to confirm correct knock sensor operation:
lKS signal level is less than the minimum threshold (dependent on engine speed) – the engine must be running,
coolant temperature above 60°C (140°F), number of camshaft revolutions since start greater than 50 and the KS
signal profile must be less than the threshold value at a given engine speed for a fault condition to be flagged
lKS signal is greater than the maximum threshold (dependent on engine speed) – the engine must be running,
coolant temperature above 60°C (140°F), number of camshaft revolutions since start greater than 50 and the KS
signal profile must be greater than the threshold value at a given engine speed for a fault condition to be flagged
lError counter for verification of knock internal circuitry exceeded – the engine must be running, coolant
temperature above 60°C (140°F), number of camshaft revolutions since start greater than 50 and the error
counter greater than the threshold value at a given engine speed for a fault condition to be flagged
Should a malfunction of the component occur the following fault codes may be evident and can be retrieved by
TestBook:
Spark plugs
The spark plugs are platinum tipped on both centre and earth electrodes. The platinum tips give a long maintenance
free life.
Cleaning or resetting the spark plug gap is not recommended as this could result in damaging the platinum tips and
thereby reducing reliability.
The misfire detection system will malfunction and store erroneous codes if the incorrect spark plugs are used.
Input/Output
The ignition coils provide a voltage to the spark plugs via the ht leads. The cylinder head via the individual thread of
each spark plug provides the earth path.
The spark plugs can fail in the following ways:
lFaulty component.
lConnector or wiring fault.
lBreakdown of high tension lead causing tracking to chassis earth.
lIncorrect spark plugs fitted.
In the event of a spark plug failure, misfire on specific cylinder may be observed:
P Code J2012 Description Land Rover Description
P0327 Knock sensor 1 circuit low input (bank 1 or single
sensor)LH bank signal less than threshold determined from
ECM model above 2200 rev/min
P0328 Knock sensor 1 circuit high input (bank 1 or
single sensor)LH bank signal greater than threshold determined from
ECM model above 2200 rev/min
P0332 Knock sensor 2 circuit low input (bank 2) RH bank signal less than threshold determined from
ECM model above 2200 rev/min
P0333 Knock sensor 2 circuit high input (bank 2) RH bank signal greater than threshold determined from
ECM model above 2200 rev/min