spark plug JEEP GRAND CHEROKEE 2003 WJ / 2.G Owner's Manual

FORM-IN-PLACE GASKET AND SEALER
APPLICATION
Assembling parts using a form-in-place gasket
requires care but it's easier then using precut gaskets.
MopartGasket Maker material should be applied
sparingly 1 mm (0.040 in.) diameter or less of sealant
to one gasket surface. Be certain the material sur-
rounds each mounting hole. Excess material can eas-
ily be wiped off. Components should be torqued in
place within 15 minutes. The use of a locating dowel
is recommended during assembly to prevent smear-
ing material off the location.
MopartEngine RTV GEN II or ATF RTV gasket
material should be applied in a continuous bead
approximately 3 mm (0.120 in.) in diameter. All
mounting holes must be circled. For corner sealing, a
3.17 or 6.35 mm (1/8 or 1/4 in.) drop is placed in the
center of the gasket contact area. Uncured sealant
may be removed with a shop towel. Components
should be torqued in place while the sealant is still
wet to the touch (within 10 minutes). The usage of a
locating dowel is recommended during assembly to
prevent smearing material off the location.
MopartGasket Sealant in an aerosol can should be
applied using a thin, even coat sprayed completely
over both surfaces to be joined, and both sides of a
gasket. Then proceed with assembly. Material in a
can w/applicator can be brushed on evenly over the
sealing surfaces. Material in an aerosol can should be
used on engines with multi-layer steel gaskets.
STANDARD PROCEDURE - REPAIR DAMAGED
OR WORN THREADS
CAUTION: Be sure that the tapped holes maintain
the original center line.
Damaged or worn threads can be repaired. Essen-
tially, this repair consists of:
²Drilling out worn or damaged threads.
²Tapping the hole with a special Heli-Coil Tap, or
equivalent.
²Installing an insert into the tapped hole to bring
the hole back to its original thread size.
STANDARD PROCEDUREÐHYDROSTATIC LOCK
CAUTION: DO NOT use the starter motor to rotate
the crankshaft. Severe damage could occur.
When an engine is suspected of hydrostatic lock
(regardless of what caused the problem), follow the
steps below.
(1) Perform the Fuel Pressure Release Procedure
(Refer to 14 - FUEL SYSTEM/FUEL DELIVERY -
STANDARD PROCEDURE).(2) Disconnect the negative cable(s) from the bat-
tery.
(3) Inspect air cleaner, induction system, and
intake manifold to ensure system is dry and clear of
foreign material.
(4) Place a shop towel around the spark plugs to
catch any fluid that may possibly be under pressure
in the cylinder head. Remove the spark plugs.
(5) With all spark plugs removed, rotate the crank-
shaft using a breaker bar and socket.
(6) Identify the fluid in the cylinders (coolant, fuel,
oil, etc.).
(7) Be sure all fluid has been removed from the
cylinders.
(8) Repair engine or components as necessary to
prevent this problem from occurring again.
(9) Squirt a small amount of engine oil into the
cylinders to lubricate the walls. This will prevent
damage on restart.
(10) Install new spark plugs. Tighten the spark
plugs to 41 N´m (30 ft. lbs.) torque.
(11) Drain engine oil. Remove and discard the oil
filter.
(12) Install the drain plug. Tighten the plug to 34
N´m (25 ft. lbs.) torque.
(13) Install a new oil filter.
(14) Fill engine crankcase with the specified
amount and grade of oil. (Refer to LUBRICATION &
MAINTENANCE - SPECIFICATIONS).
(15) Connect the negative cable(s) to the battery.
(16) Start the engine and check for any leaks.
STANDARD PROCEDURE - CYLINDER BORE
HONING
Before honing, stuff plenty of clean shop towels
under the bores and over the crankshaft to keep
abrasive materials from entering the crankshaft
area.
(1)
Used carefully, the Cylinder Bore Sizing Hone
C-823, equipped with 220 grit stones, is the best tool
for this job. In addition to deglazing, it will reduce
taper and out-of-round, as well as removing light scuff-
ing, scoring and scratches. Usually, a few strokes will
clean up a bore and maintain the required limits.
CAUTION: DO NOT use rigid type hones to remove
cylinder wall glaze.
(2) Deglazing of the cylinder walls may be done if
the cylinder bore is straight and round. Use a cylin-
der surfacing hone, Honing Tool C-3501, equipped
with 280 grit stones (C-3501-3810). about 20-60
strokes, depending on the bore condition, will be suf-
ficient to provide a satisfactory surface. Using honing
oil C-3501-3880, or a light honing oil, available from
major oil distributors.
9 - 10 ENGINE - 4.0LWJ
ENGINE - 4.0L (Continued)

DESCRIPTION N´m Ft. In.
Lbs. Lbs.
Transmission Support Bracket
ÐBolt (Manual) 46 34 Ð
Transmission Support Bracket/
CushionÐBolt (4WD Auto) 75 55 Ð
Transmission Support Adaptor
BracketÐBolts (2WD Auto) 75 55 Ð
Exhaust Manifold/PipeÐNuts 27 20 Ð
Intake/Exhaust Manifold
Fasteners #1-5 33 24 Ð
Fasteners #6 and 7 14 Ð 126
Fasteners #8-11 33 24 Ð
Flywheel to Converter
HousingÐBolts38 28 Ð
Flywheel to CrankshaftÐBolts 143 105 Ð
Front Cover to BlockÐBolts
1/4-20 7 Ð 60
5/16-18 22 Ð 192
Fuel RailÐBolts/Stud 12 Ð 108
GeneratorÐBolts 57 42 Ð
Generator Bracket to EngineÐ
Bolts47 35 Ð
Idler Pulley to Cylinder
HeadÐBolt47 35 Ð
Main Bearing CapÐBolts 108 80 Ð
Oil Filter 18 Ð 156
Oil Filter Connector to
Adaptor 47 35 Ð
Block 68 50 Ð
Adaptor Bolts 102 50 Ð
Oil GalleyÐPlug 41 30 Ð
Oil PanÐBolts
1/4-20 9.5 Ð 84
5/16-18 15 Ð 132
Oil PanÐDrain Plug 34 25 Ð
Oil Pump
Mounting Bolts 23 Ð 204
Cover Bolts 8 Ð 70
Rocker Arm Assembly to
Cylinder
HeadÐCapscrews 30 21 Ð
Spark Plugs 37 27 ÐDESCRIPTION N´m Ft. In.
Lbs. Lbs.
Starter MotorÐMounting Bolts 45 33 Ð
Thermostat HousingÐBolts 18 Ð 156
Throttle BodyÐBolts 10 Ð 90
Vibration DamperÐBolt 108 80 Ð
Water Pump to BlockÐBolts 23 17 Ð
AIR CLEANER ELEMENT
REMOVAL - 4.0L
(1) Unlatch four clips retaining air cleaner cover to
air cleaner housing (Fig. 6).
Fig. 6 Air Cleaner Assembly Ð4.0L Engine
1 - RESONATOR BOLTS
2 - CLAMPS
3 - AIR DUCT
4 - AIR CLEANER COVER
5 - CLIPS
6 - HOUSING
7 - HOUSING BOLTS (3)
8 - LOWER HOUSING NUTS (3)
9 - RESONATOR
9 - 18 ENGINE - 4.0LWJ
ENGINE - 4.0L (Continued)

(2) Drain the coolant (Refer to 7 - COOLING -
STANDARD PROCEDURE) and disconnect the hoses
at the engine thermostat housing and the water
pump inlet. DO NOT waste reusable coolant. If the
solution is clean and is being drained only to service
the engine or cooling system, drain the coolant into a
clean container for reuse.
(3) Remove the air cleaner assembly (Refer to 9 -
ENGINE/AIR INTAKE SYSTEM/AIR CLEANER
HOUSING - REMOVAL).
(4) Remove the cylinder head cover (Refer to 9 -
ENGINE/CYLINDER HEAD/CYLINDER HEAD
COVER(S) - REMOVAL).
(5) Remove the capscrews, bridge and pivot assem-
blies and rocker arms (Refer to 9 - ENGINE/CYLIN-
DER HEAD/ROCKER ARM / ADJUSTER ASSY -
REMOVAL).
(6) Remove the push rods.Retain the push rods,
bridges, pivots and rocker arms in the same
order as removed.
(7) Remove the accessory drive belt (Refer to 7 -
COOLING/ACCESSORY DRIVE/DRIVE BELTS -
REMOVAL).
(8) Remove the A/C compressor mounting bolts
and secure the compressor to the side.
(9) Remove the power steering pump and bracket
from the intake manifold and water pump. Set the
pump and bracket aside. DO NOT disconnect the
hoses.
(10) Perform the Fuel System Pressure Release
procedure. (Refer to 14 - FUEL SYSTEM/FUEL
DELIVERY - STANDARD PROCEDURE).
(11) Disconnect the fuel supply line at the fuel rail.(12) Remove the intake and exhaust manifolds
from the engine cylinder head (Refer to 9 - ENGINE/
MANIFOLDS/INTAKE MANIFOLD - REMOVAL).
(13) Remove the coil rail (Refer to 8 - ELECTRI-
CAL/IGNITION CONTROL/COIL RAIL - REMOV-
AL).
(14) Remove spark plugs (Refer to 8 - ELECTRI-
CAL/IGNITION CONTROL/SPARK PLUG - REMOV-
AL).
(15) Disconnect the temperature sending unit wire
connector.
(16) Remove the engine cylinder head bolts. Bolt
No.14 cannot be removed until the head is moved for-
ward (Fig. 9). Pull bolt No.14 out as far as it will go
and then suspend the bolt in this position (tape
around the bolt).
(17) Remove the engine cylinder head and gasket
(Fig. 9).
(18) If this was the first time the bolts were
removed, put a paint dab on the top of the bolt. If the
bolts have a paint dab on the top of the bolt or it
isn't known if they were used before, discard the
bolts.
(19) Stuff clean lint free shop towels into the cyl-
inder bores.
NOTE: If the valves, springs, or seals are to be
inspected/replaced at this time, (Refer to 9 -
ENGINE/CYLINDER HEAD/INTAKE/EXHAUST
VALVES & SEATS - STANDARD PROCEDURE) for
proper inspection procedures.
Fig. 8 Cylinder Head 4.0L Engine
1 - CYLINDER HEAD BOLTS
2 - CYLINDER HEAD GASKET
3 - CYLINDER HEAD
Fig. 9 Engine Cylinder
1 - CYLINDER HEAD BOLTS
2 - CYLINDER HEAD GASKET
3 - CYLINDER HEAD
9 - 20 ENGINE - 4.0LWJ
CYLINDER HEAD (Continued)

CLEANING
Thoroughly clean the engine cylinder head and cyl-
inder block mating surfaces. Clean the intake and
engine exhaust manifold and engine cylinder head
mating surfaces. Remove all gasket material and car-
bon.
Check to ensure that no coolant or foreign material
has fallen into the tappet bore area.
Remove the carbon deposits from the combustion
chambers and top of the pistons.
INSPECTION
Use a straightedge and feeler gauge to check the
flatness of the engine cylinder head and block mating
surfaces.
INSTALLATION
NOTE: This procedure can be done with the engine
in or out of the vehicle.
The engine cylinder head gasket is a composition
gasket. The gasket is to be installed DRY.DO NOT
use a gasket sealing compound on the gasket.
If the engine cylinder head is to be replaced and
the original valves used, measure the valve stem
diameter. Only standard size valves can be used with
a service replacement engine cylinder head unless
the replacement head valve stem guide bores are
reamed to accommodate oversize valve stems.
Remove all carbon buildup and reface the valves.
(1) Remove the shop towels from the cylinder
bores. Coat the bores with clean engine oil.
(2) Position the engine cylinder head gasket (with
the numbers facing up) using the alignment dowels
in the cylinder block, to position the gasket.
CAUTION: Engine cylinder head bolts should be
reused only once. Replace the head bolts if they
were used before or if they have a paint dab on the
top of the bolt.
(3) With bolt No.14 held in place (tape around
bolt), install the engine cylinder head over the same
dowels used to locate the gasket. Remove the tape
from bolt No.14.
(4) Coat the threads of stud bolt No.11 with Loc-
tite 592 sealant, or equivalent.
(5) Tighten the engine cylinder head bolts in
sequence according to the following procedure (Fig.
10).
CAUTION: During the final tightening sequence,
bolt No.11 will be tightened to a lower torque than
the rest of the bolts. DO NOT overtighten bolt
No.11.(a) Tighten all bolts in sequence (1 through 14)
to 30 N´m (22 ft. lbs.) torque.
(b) Tighten all bolts in sequence (1 through 14)
to 61 N´m (45 ft. lbs.) torque.
(c) Check all bolts to verify they are set to 61
N´m (45 ft. lbs.) torque.
(d) Tighten bolts in sequence:
²Bolts 1 through 10 to 149 N´m (110 ft. lbs.)
torque.
²Bolt 11 to 135 N´m (100 ft. lbs.) torque.
²Bolts 12 through 14 to 149 N´m (110 ft. lbs.)
torque.
CYLINDER HEAD BOLTS
POSITION DESCRIPTION
1,4,5,12,13 1/2 in.-13 BOLT
8,9 1/2 in.-13 BOLT WITH DOWEL
POINT
2,3,6,7,10,11,14 1/2 in.-13 WITH 7/16 in.-14 STUD
END
All bolts are 12 point drives for rocker cover clearance
(e) Check all bolts in sequence to verify the cor-
rect torque.
(f) If not already done, clean and mark each bolt
with a dab of paint after tightening. Should you
encounter bolts which were painted in an earlier
service operation, replace them.
(6) Install the spark plugs (Refer to 8 - ELECTRI-
CAL/IGNITION CONTROL/SPARK PLUG - INSTAL-
LATION).
(7) Connect the temperature sending unit wire
connector.
(8) Install the ignition coil rail (Refer to 8 - ELEC-
TRICAL/IGNITION CONTROL/COIL RAIL -
INSTALLATION).
(9) Install the intake and exhaust manifolds (Refer
to 9 - ENGINE/MANIFOLDS/INTAKE MANIFOLD -
INSTALLATION).
(10) Install the fuel line.
(11) Attach the power steering pump and bracket.
Fig. 10 Engine Cylinder Head Bolt Tightening
Sequence
WJENGINE - 4.0L 9 - 21
CYLINDER HEAD (Continued)

(2) Remove cap screws, bridge and pivot assem-
blies and rocker arms (Refer to 9 - ENGINE/CYLIN-
DER HEAD/ROCKER ARM / ADJUSTER ASSY -
REMOVAL) for access to each valve spring to be
removed.
(3) Remove push rods.Retain the push rods,
bridges, pivots and rocker arms in the same
order and position as removed.
(4) Inspect the springs and retainer for cracks and
possible signs of weakening.
(5) Remove the spark plug(s) adjacent to the cylin-
der(s) below the valve springs to be removed.
(6) Connect an air hose to the adapter and apply
air pressure slowly. Maintain at least 621 kPa (90
psi) of air pressure in the cylinder to hold the valves
against their seats. For vehicles equipped with an air
conditioner, use a flexible air adaptor when servicing
the No.1 cylinder.
(7) Tap the retainer or tip with a rawhide hammer
to loosen the lock from the retainer. Use Valve Spring
Compressor Tool MD-998772A to compress the spring
and remove the locks (Fig. 27).
(8) Remove valve spring and retainer (Fig. 27).
(9) Remove valve stem oil seals (Fig. 27). Note the
valve seals are different for intake and exhaust
valves. The top of each seal is marked either INT
(intake/black in color) or EXH (exhaust/brown in
color). DO NOT mix the seals.
INSTALLATION
NOTE: This procedure can be done with the engine
cylinder head installed on the block.
CAUTION: Install oil seals carefully to prevent dam-
age from the sharp edges of the valve spring lock
grove.
(1) Lightly push the valve seal over the valve stem
and valve guide boss. Be sure the seal is completely
seated on the valve guide boss.
(2) Install valve spring and retainer (Fig. 28).
(3) Compress the valve spring with Valve Spring
Compressor Tool MD-998772A and insert the valve
locks. Release the spring tension and remove the
tool. Tap the spring from side-to-side to ensure that
the spring is seated properly on the engine cylinder
head.(4) Release air pressure and disconnect the air
hose. Remove the adaptor from the spark plug hole
and install the spark plug.
(5) Repeat the procedures for each remaining valve
spring to be removed.
(6) Install the push rods. Ensure the bottom end of
each rod is centered in the plunger cap seat of the
hydraulic valve tappet.
(7) Install the rocker arms, pivots and bridge
(Refer to 9 - ENGINE/CYLINDER HEAD/ROCKER
ARM / ADJUSTER ASSY - INSTALLATION) at their
original location.
(8) Install the engine cylinder head cover (Refer to
9 - ENGINE/CYLINDER HEAD/CYLINDER HEAD
COVER(S) - INSTALLATION).
Fig. 27 Valve and Valve Components
1 - VALVE LOCKS (3±BEAD)
2 - RETAINER
3 - VALVE STEM OIL SEAL
4 - INTAKE VALVE
5 - EXHAUST VALVE
6 - VALVE SPRING
WJENGINE - 4.0L 9 - 29
VALVE SPRINGS (Continued)

REMOVAL
(1) Disconnect negative cable from battery.
(2) Remove the spark plugs (Refer to 8 - ELEC-
TRICAL/IGNITION CONTROL/SPARK PLUG -
REMOVAL).
(3) Raise the vehicle.
(4) Remove the oil pan (Refer to 9 - ENGINE/LU-
BRICATION/OIL PAN - REMOVAL) and oil pump
(Refer to 9 - ENGINE/LUBRICATION/OIL PUMP -
REMOVAL).
(5) Remove main bearing cap brace (Fig. 44).
(6) Remove only one main bearing cap and lower
insert at a time (Fig. 45).
(7) Remove the lower insert from the bearing cap.
(8) Remove the upper insert by LOOSENING (DO
NOT REMOVE) all of the other bearing caps. Now
insert a small cotter pin tool in the crankshaft jour-
nal oil hole. Bend the cotter pin as illustrated to fab-
ricate the tool (Fig. 46). With the cotter pin tool in
place, rotate the crankshaft so that the upper bear-
ing insert will rotate in the direction of its locking
tab. Because there is no hole in the No.3 main jour-
nal, use a tongue depressor or similar soft-faced tool
to remove the bearing insert (Fig. 46). After moving
the insert approximately 25 mm (1 inch), it can be
removed by applying pressure under the tab.
(9) Using the same procedure described above,
remove the remaining bearing inserts one at a time
for inspection.
Fig. 44 Main Bearing Caps and Brace.
1 - BLOCK
2 - MAIN BEARING CAP BRACE
Fig. 45 Removing Main Bearing Caps and Lower
Inserts
1 - CONNECTING ROD JOURNAL
2 - MAIN BEARING CAPS
Fig. 46 Removing Upper Inserts
1 - COTTER PIN
2 - BEARING INSERT
3 - TONGUE DEPRESSOR
WJENGINE - 4.0L 9 - 39
CRANKSHAFT MAIN BEARINGS (Continued)

(e) If end play is not within specification, inspect
crankshaft thrust faces for wear. If no wear is
apparent, replace the thrust bearing and measure
end play. If end play is still not within specifica-
tion, replace the crankshaft.
(11) If the crankshaft was removed, install the
crankshaft into the cylinder block.
(12) Install main bearing cap brace tighten nuts to
47 N´m (35 ft. lbs.) torque.
(13) Install oil pump assy. and tighten attaching
bolts to 23 N´m (17 ft. lbs.)
(14) Install the oil pan (Refer to 9 - ENGINE/LU-
BRICATION/OIL PAN - INSTALLATION).
(15) Install the drain plug. Tighten the plug to 34
N´m (25 ft. lbs.) torque.
(16) Lower the vehicle.
(17) Install the spark plugs. Tighten the plugs to
37 N´m (27 ft. lbs.) torque.
(18) Fill the oil pan with engine oil to the full
mark on the dipstick level.
(19) Connect negative cable to battery.
CRANKSHAFT OIL SEAL -
FRONT
REMOVAL
This procedure is done with the timing case cover
installed.
(1) Disconnect negative cable from battery.
(2) Remove the serpentine drive belt (Refer to 7 -
COOLING/ACCESSORY DRIVE/DRIVE BELTS -
REMOVAL).(3) Remove the vibration damper (Refer to 9 -
ENGINE/ENGINE BLOCK/VIBRATION DAMPER -
REMOVAL).
(4) Remove the radiator shroud.
(5) Carefully remove the oil seal. Make sure seal
bore is clean.
INSTALLATION
This procedure is done with the timing case cover
installed.
(1) Position the replacement oil seal on Timing
Case Cover Alignment and Seal Installation Tool
6139 with seal open end facing inward. Apply a light
film of Perfect Seal, or equivalent, on the outside
diameter of the seal. Lightly coat the crankshaft with
engine oil.
(2) Position the tool and seal over the end of the
crankshaft and insert a draw screw tool into Seal
Installation Tool 6139 (Fig. 50). Tighten the nut
against the tool until it contacts the cover.
(3) Remove the tools. Apply a light film of engine
oil on the vibration damper hub contact surface of
the seal.
(4) Apply MopartSilicone Rubber Adhesive Seal-
ant to the keyway in the crankshaft and insert the
key. With the key inserted in the keyway in the
crankshaft, install the vibration damper (Refer to 9 -
ENGINE/ENGINE BLOCK/VIBRATION DAMPER -
INSTALLATION).
(5) Install the serpentine belt (Refer to 7 - COOL-
ING/ACCESSORY DRIVE/DRIVE BELTS - INSTAL-
LATION).
(6) Install the radiator shroud.
(7) Connect negative cable to battery.
Fig. 49 Crankshaft End Play Measurement
1 - DIAL INDICATOR
2 - CRANKSHAFT
Fig. 50 Timing Case Cover Oil Seal Installation
1 - SEAL INSTALLATION TOOL
2 - DRAW SCREW TOOL
WJENGINE - 4.0L 9 - 41
CRANKSHAFT MAIN BEARINGS (Continued)

DIAGNOSIS AND TESTING - ENGINE DIAGNOSIS - PERFORMANCE
CONDITION POSSIBLE CAUSE CORRECTION
ENGINE WILL NOT START 1. Weak battery 1. Charge or replace as necessary.
2. Corroded or loose battery
connections.2. Clean and tighten battery
connections. Apply a coat of light
mineral grease to the terminals.
3. Faulty starter. 3. (Refer to 8 - ELECTRICAL/
STARTING - DIAGNOSIS AND
TESTING).
4. Faulty coil or control unit. 4. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/IGNITION COIL -
REMOVAL).
5. Incorrect spark plug gap. 5. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/SPARK PLUG -
CLEANING).
6. Dirt or water in fuel system. 6. Clean system and replace fuel filter.
7. Faulty fuel pump, relay or wiring. 7. Repair or replace as necessary.
ENGINE STALLS OR ROUGH
IDLE1. Idle speed set to low. 1. (Refer to 14 - FUEL SYSTEM/FUEL
INJECTION/IDLE AIR CONTROL
MOTOR - REMOVAL).
2. Idle mixture to lean or to rich. 2. Refer to Powertrain Diagnosis
Information.
3. Vacuum leak. 3. Inspect intake manifold and vacuum
hoses, repair or replace as necessary.
4. Faulty coil. 4. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/IGNITION COIL -
REMOVAL).
5. Incorrect engine timing. 5. (Refer to 9 - ENGINE/VALVE
TIMING - STANDARD PROCEDURE).
1. ENGINE LOSS OF POWER 1. Dirty or incorrectly gapped spark
plugs.1. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/SPARK PLUG -
CLEANING).
2. Dirt or water in fuel system. 2. Clean system and replace fuel filter.
3. Faulty fuel pump. 3. (Refer to 14 - FUEL SYSTEM/FUEL
DELIVERY/FUEL PUMP - DIAGNOSIS
AND TESTING).
4. Blown cylinder head gasket. 4. Replace cylinder head gasket.
5. Low compression. 5. (Refer to 9 - ENGINE - DIAGNOSIS
AND TESTING), repair as necessary.
6. Burned, warped or pitted valves. 6. Replace as necessary.
7. Plugged or restricted exhaust
system.7. Inspect and replace as necessary.
8. Faulty coil. 8. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/IGNITION COIL -
REMOVAL).
WJENGINE - 4.7L 9 - 65
ENGINE - 4.7L (Continued)

CONDITION POSSIBLE CAUSE CORRECTION
1. ENGINE MISSES ON
ACCELERATION1. Spark plugs dirty or incorrectly
gapped.1. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/SPARK PLUG -
CLEANING).
2. Dirt in fuel system. 2. Clean fuel system.
3. Burned, warped or pitted valves. 3. Replcae as necessary.
4. Faulty coil. 4. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/IGNITION COIL -
REMOVAL).
1. ENGINE MISSES AT HIGH
SPEED1. Spark plugs dirty or incorrectly
gapped.1. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/SPARK PLUG -
CLEANING).
2. Faulty coil. 2. (Refer to 8 - ELECTRICAL/
IGNITION CONTROL/IGNITION COIL -
REMOVAL).
3. Dirt or water in fuel system. 3. Clean system and replace fuel filter.
DIAGNOSIS AND TESTING - ENGINE DIAGNOSIS - MECHANICAL
CONDITION POSSIBLE CAUSES CORRECTIONS
NOISY VALVES 1. High or low oil level in crankcase. 1. (Refer to LUBRICATION &
MAINTENANCE/FLUID TYPES -
SPECIFICATIONS).
2. Thin or diluted oil. 2. Change oil and filter.
3. Low oil pressure. 3. Check oil pump, if Ok, check rod
and main bearings for excessive wear.
4. Dirt in lash adjusters. 4. Replace as necessary.
5. Worn rocker arms. 5. Replace as necessary.
6. Worn lash adjusters 6. Replace as necessary.
7. Worn valve guides. 7. (Refer to 9 - ENGINE/CYLINDER
HEAD/INTAKE/EXHAUST VALVES &
SEATS - STANDARD PROCEDURE).
8. Excessive runout of valve seats
on valve faces.8. Service valves and valve seats.
(Refer to 9 - ENGINE/CYLINDER
HEAD/INTAKE/EXHAUST VALVES &
SEATS - STANDARD PROCEDURE).
CONNECTING ROD NOISE 1. Insufficient oil supply. 1. (Refer to LUBRICATION &
MAINTENANCE/FLUID TYPES -
SPECIFICATIONS).
2. Low oil pressure. 2. Check oil pump, if Ok, check rod
and main bearings for excessive wear.
3. Thin or diluted oil. 3. Change oil and filter.
4. Excessive bearing clearance. 4. Replace as necessary.
5. Connecting rod journal out-of-
round.5. Service or replace crankshaft.
6. Misaligned connecting rods. 6. Replace bent connecting rods.
9 - 66 ENGINE - 4.7LWJ
ENGINE - 4.7L (Continued)

CONDITION POSSIBLE CAUSES CORRECTION
OIL PRESSURE DROP 1. Low oil level. 1. Check and correct oil level.
2. Faulty oil pressure sending unit. 2. Replace sending unit (Refer to 9 -
ENGINE/LUBRICATION/OIL
PRESSURE SENSOR/SWITCH -
REMOVAL).
3. Low oil pressure. 3. Check oil pump and bearing
clearance.
4. Clogged oil filter. 4. Replace oil filter (Refer to 9 -
ENGINE/LUBRICATION/OIL FILTER -
REMOVAL).
5. Worn oil pump. 5. Replace oil pump (Refer to 9 -
ENGINE/LUBRICATION/OIL PUMP -
REMOVAL).
6. Thin or diluted oil. 6. Change oil and filter.
7. Excessive bearing clearance. 7. Replace as necessary.
8. Oil pump relief valve stuck. 8. Replace oil pump (Refer to 9 -
ENGINE/LUBRICATION/OIL PUMP -
REMOVAL).
9. Oil pick up tube loose, damaged
or clogged.9. Replace as necessary.
OIL PUMPING AT RINGS;
SPARK PLUGS FOULING1. Worn or damaged rings. 1. Hone cylinder bores and replace
rings.
2. Carbon in oil ring slots. 2. Replace rings (Refer to 9 -
ENGINE/ENGINE BLOCK/PISTON
RINGS - STANDARD PROCEDURE).
3. Incorrect ring size installed. 3. Replace rings (Refer to 9 -
ENGINE/ENGINE BLOCK/PISTON
RINGS - STANDARD PROCEDURE).
4. Worn valve guides. 4. Ream guides and replace valves
(Refer to 9 - ENGINE/CYLINDER
HEAD/INTAKE/EXHAUST VALVES &
SEATS - STANDARD PROCEDURE).
5. Leaking valve guide seals. 5. Replace valve guide seals.
DIAGNOSIS AND TESTING - CYLINDER
COMPRESSION PRESSURE
The results of a cylinder compression pressure test
can be utilized to diagnose several engine malfunc-
tions.
Ensure the battery is completely charged and the
engine starter motor is in good operating condition.
Otherwise the indicated compression pressures may
not be valid for diagnosis purposes.
(1) Clean the spark plug recesses with compressed
air.
(2) Remove the spark plugs.
(3) Secure the throttle in the wide-open position.(4) Disable the fuel system (Refer to 14 - FUEL
SYSTEM/FUEL DELIVERY - DESCRIPTION).
(5) Remove the ASD relay (Refer to 8 - ELECTRI-
CAL/IGNITION CONTROL/AUTO SHUT DOWN
RELAY - REMOVAL).
(6) Insert a compression pressure gauge and rotate
the engine with the engine starter motor for three
revolutions.
(7) Record the compression pressure on the 3rd
revolution. Continue the test for the remaining cylin-
ders.
(8) (Refer to 9 - ENGINE - SPECIFICATIONS) for
the correct engine compression pressures.
9 - 68 ENGINE - 4.7LWJ
ENGINE - 4.7L (Continued)