2002 JEEP GRAND CHEROKEE ENGINE CONTROL

INSPECTION
Inspect the pivot surface area of each rocker arm.
Replace any that are scuffed, pitted, cracked or
excessively worn.
Inspect the valve stem tip contact surface of each
rocker arm and replace any rocker arm that is deeply
pitted.
Inspect each push rod end for excessive wear and
replace as required. If any push rod is excessively
worn because of lack of oil, replace it and inspect the
corresponding hydraulic tappet for excessive wear.
Inspect the push rods for straightness by rolling
them on a flat surface or by shining a light between
the push rod and the flat surface.
A wear pattern along the length of the push rod is
not normal. Inspect the engine cylinder head for
obstruction if this condition exists.
INSTALLATION
NOTE: This procedure can be done with the engine
in or out of the vehicle.
(1) Lubricate the ball ends of the push rods with
MopartEngine Oil Supplement, or equivalent and
install push rods in their original locations. Ensurethat the bottom end of each push rod is centered in
the tappet plunger cap seat.
(2) Using MopartEngine Oil Supplement, or
equivalent, lubricate the area of the rocker arm that
the pivot contacts. Install rocker arms, pivots and
bridge above each cylinder in their originally position
(Fig. 23).
(3) Loosely install the capscrews through each
bridge.
(4) At each bridge, tighten the capscrews alter-
nately, one turn at a time, to avoid damaging the
bridge. Tighten the capscrews to 28 N´m (21 ft. lbs.)
torque.
(5) Install the engine cylinder head cover (Refer to
9 - ENGINE/CYLINDER HEAD/CYLINDER HEAD
COVER(S) - INSTALLATION).
VALVE STEM SEALS
DESCRIPTION
The valve stem seals (Fig. 24) are made of rubber
and incorporate a garter spring to maintain consis-
tent lubrication control.
Fig. 22 Rocker Arm
1 - CAPSCREWS
2 - BRIDGE
3 - PIVOT ASSEMBLY
4 - PUSH RODS
5 - ROCKER ARMS
Fig. 23 Rocker Arm
1 - CAPSCREWS
2 - BRIDGE
3 - PIVOT ASSEMBLY
4 - PUSH RODS
5 - ROCKER ARMS
WJENGINE - 4.0L 9 - 27
ROCKER ARM / ADJUSTER ASSEMBLY (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)

INSPECTION
Wipe the inserts clean and inspect for abnormal
wear patterns and for metal or other foreign material
imbedded in the lining. Normal main bearing insert
wear patterns are illustrated (Fig. 47). In general the
lower bearing half will have a heaver wear pattern.
NOTE: If any of the crankshaft journals are scored,
remove the engine for crankshaft repair.
Inspect the back of the inserts for fractures, scrap-
ings or irregular wear patterns.
Inspect the upper insert locking tabs for damage.
Replace all damaged or worn bearing inserts.
INSTALLATION
(1) Lubricate the bearing surface of each insert
with engine oil.
(2) Loosen all the main bearing caps. Install the
main bearing upper inserts.
(3) Install the lower bearing inserts into the main
bearing caps.
(4) On the rear main cap, apply MopartGasket
Maker sealer on both sides of cylinder block as
shown in (Fig. 48). The dab of sealer should be 3 mm
(0.125 in.) in diameter.
(5) Apply MopartGasket Maker on the rear bear-
ing cap. The bead should be 2.3 mm (0.09 in.) in
diameter. DO NOT apply sealer to the lip of the seal.
(6) Install the main bearing cap(s) and lower
insert(s).
(7) Tighten the bolts of caps 1, 2, 4, 5, 6, and 7 to
54 N´m (40 ft. lbs.) torque. Now tighten these bolts to
95 N´m (70 ft. lbs.) torque. Finally, tighten these
bolts to 108 N´m (80 ft. lbs.) torque.(8) Push the crankshaft forward and backward.
Load the crankshaft front or rear and tighten cap
bolt No.3 to 54 N´m (40 ft. lbs.) torque. Then tighten
to 95 N´m (70 ft. lbs.) torque and finally tighten to
108 N´m (80 ft. lbs.) torque.
(9) Rotate the crankshaft after tightening each
main bearing cap to ensure the crankshaft rotates
freely.
(10) Check crankshaft end play. Crankshaft end
play is controlled by the thrust bearing which is
flange and installed at the No.2 main bearing posi-
tion.
(a) Attach a magnetic base dial indicator to the
cylinder block at either the front or rear of the
engine.
(b) Position the dial indicator rod so that it is
parallel to the center line of the crankshaft.
(c) Pry the crankshaft forward, position the dial
indicator to zero.
(d) Pry the crankshaft forward and backward.
Note the dial indicator readings. End play is the
difference between the high and low measurements
(Fig. 49). Correct end play is 0.038-0.165 mm
(0.0015-0.0065 inch). The desired specifications are
0.051-0.064 mm (0.002-0.0025 inch).
Fig. 47 Main Bearing Wear Patterns
1 - UPPER INSERT
2 - NO WEAR IN THIS AREA
3 - LOW AREA IN BEARING LINING
4 - LOWER INSERT
Fig. 48 Location of Sealer
1-DOWEL
2-SEALER LOCATIONS
3-CYLINDER BLOCK
4-HALFWAY BETWEEN
5-REAR FACE OF CYLINDER BLOCK
6-3mm (0.125 in.)
9 - 40 ENGINE - 4.0LWJ
CRANKSHAFT MAIN BEARINGS (Continued)

HYDRAULIC LIFTERS
DESCRIPTION
Valve lash is controlled by hydraulic tappets
located inside the cylinder block, in tappet bores
above the camshaft.
REMOVAL
NOTE: Retain all the components in the same order
as removed.
(1) Remove the engine cylinder head(Refer to 9 -
ENGINE/CYLINDER HEAD - REMOVAL).
(2) Remove the push rods.
(3) Remove the tappets through the push rod open-
ings in the cylinder block with a Hydraulic Valve
Tappet Removal/Installation Tool (Fig. 53).
CLEANING
Clean each tappet assembly in cleaning solvent to
remove all varnish, gum and sludge deposits.
INSPECTION
Inspect for indications of scuffing on the side and
base of each tappet body.
Inspect each tappet base for concave wear with a
straightedge positioned across the base. If the base is
concave, the corresponding lobe on the camshaft is
also worn. Replace the camshaft and tappets.
After cleaning and inspection, test each tappet for
specified leak-down rate tolerance to ensure zero-lash
operation (Fig. 54).
Swing the weighted arm of the hydraulic valve tap-
pet tester away from the ram of the Leak-Down
Tester.
(1) Place a 7.925-7.950 mm (0.312-0.313 inch)
diameter ball bearing on the plunger cap of the tap-
pet.(2) Lift the ram and position the tappet (with the
ball bearing) inside the tester cup.
(3) Lower the ram, then adjust the nose of the ram
until it contacts the ball bearing. DO NOT tighten
the hex nut on the ram.
(4) Fill the tester cup with hydraulic valve tappet
test oil until the tappet is completely submerged.
(5) Swing the weighted arm onto the push rod and
pump the tappet plunger up and down to remove air.
When the air bubbles cease, swing the weighted arm
away and allow the plunger to rise to the normal
position.
(6) Adjust the nose of the ram to align the pointer
with the SET mark on the scale of the tester and
tighten the hex nut.
(7) Slowly swing the weighted arm onto the push
rod.
(8) Rotate the cup by turning the handle at the
base of the tester clockwise one revolution every 2
seconds.
(9) Observe the leak-down time interval from the
instant the pointer aligns with the START mark on
the scale until the pointer aligns with the 0.125
mark. A normally functioning tappet will require
20-110 seconds to leak-down. Discard tappets with
leak-down time interval not within this specification.
INSTALLATION
Retain all the components in the same order as
removed.
Fig. 53 HYDRAULIC VALVE TAPPET REMOVAL -
4.0L
1 - HYDRAULIC TAPPET REMOVAL TOOL
2 - CYLINDER BLOCK
Fig. 54 Leak-Down Tester
1 - POINTER
2 - WEIGHTED ARM
3 - RAM
4 - CUP
5 - HANDLE
6 - PUSH ROD
WJENGINE - 4.0L 9 - 43

(12) Install the oil pan and gasket (Refer to 9 -
ENGINE/LUBRICATION/OIL PAN - INSTALLA-
TION).
(13) Lower the vehicle.
(14) Install the engine cylinder head (Refer to 9 -
ENGINE/CYLINDER HEAD - INSTALLATION),
push rods, rocker arms, bridges, pivots and engine
cylinder head cover(Refer to 9 - ENGINE/CYLINDER
HEAD/CYLINDER HEAD COVER(S) - INSTALLA-
TION).
(15) Fill the crankcase with engine oil.
PISTON RINGS
STANDARD PROCEDURE - PISTON RING
FITTING
(1) Carefully clean the carbon from all ring
grooves. Oil drain openings in the oil ring groove and
pin boss must be clear. DO NOT remove metal from
the grooves or lands. This will change ring-to-groove
clearances and will damage the ring-to-land seating.
(2) Be sure the piston ring grooves are free of
nicks and burrs.
(3) Measure the ring side clearance with a feeler
gauge fitted snugly between the ring land and ring
(Fig. 62) (Fig. 63). Rotate the ring in the groove. It
must move freely around circumference of the groove.
RING SIDE CLEARANCE CHART
ITEM SPECIFICATION
Top Compression Ring 0.042 - 0.084 mm
(0.0017 - 0.0033 in.)
Second Compression
Ring0.042 - 0.084 mm
(0.0017 - 0.0033 in.)
Oil Control Ring 0.06 - 0.21 mm
(0.0024 - 0.0083 in.)
(4) Place ring in the cylinder bore and push down
with inverted piston to position near lower end of the
ring travel. Measure ring gap with a feeler gauge fit-
ting snugly between ring ends (Fig. 64).
RING GAP MEASUREMENT CHART
ITEM SPECIFICATION
Top Compression Ring 0.229 - 0.610 mm
(0.0090 - 0.0240 in.)
Second Compression
Ring0.483 - 0.965 mm
(0.0190 - 0.080 in.)
Oil Control Ring 0.254 - 1.500 mm
(0.010 - 0.060 in.)
Fig. 62 Piston Dimensions
Fig. 63 Ring Side Clearance Measurement
1 - FEELER GAUGE
WJENGINE - 4.0L 9 - 47
PISTON & CONNECTING ROD (Continued)

(5) The oil control rings are symmetrical, and can
be installed with either side up. It is not necessary to
use a tool to install the upper and lower rails. Insert
oil rail spacer first, then side rails.
(6) The two compression rings are different and
cannot be interchanged. The top compression ring
can be identified by the shiny coating on the outer
sealing surface and can be installed with either side
up. (Fig. 65).
(7) The second compression ring has a slight
chamfer on the bottom of the inside edge and a dot
on the top for correct installation (Fig. 66) and (Fig.
67).
(8) Using a ring installer, install the second com-
pression ring with the dot facing up (Fig. 66) (Fig.
68).
(9) Using a ring installer, install the top compres-
sion ring (either side up).
Ring Gap Orientation
²Position the gaps on the piston as shown (Fig.
69).
²Oil spacer - Gap on center line of piston skirt.
²Oil rails - gap 180É apart on centerline of piston
pin bore.
²No. 2 Compression ring - Gap 180É from top oil
rail gap.
²No. 1 Compression ring - Gap 180É from No. 2
compression ring gap.
Fig. 64 Gap Measurement
1 - FEELER GAUGE
Fig. 65 Top Compression ring identification
1 - TOP COMPRESSION RING
Fig. 66 Second Compression Ring Identification
1 - SECOND COMPRESSION RING
2 - CHAMFER
3 - ONE DOT
Fig. 67 Compression Ring Chamfer Location
1 - TOP COMPRESSION RING
2 - SECOND COMPRESSION RING
3 - PISTON
4 - CHAMFER
9 - 48 ENGINE - 4.0LWJ
PISTON RINGS (Continued)

VIBRATION DAMPER
REMOVAL
(1) Disconnect negative cable from battery.
(2) Remove the serpentine drive belt (Refer to 7 -
COOLING/ACCESSORY DRIVE/DRIVE BELTS -
REMOVAL) and fan shroud.
(3) Remove the vibration damper retaining bolt
and washer.
(4) Use Vibration Damper Removal Tool 7697 to
remove the damper from the crankshaft (Fig. 70).
INSTALLATION
(1) Apply MopartSilicone Rubber Adhesive Seal-
ant to the keyway in the crankshaft and insert the
key. With the key in position, align the keyway on
the vibration damper hub with the crankshaft key
and tap the damper onto the crankshaft.
(2) Install the vibration damper retaining bolt and
washer.
(3) Tighten the damper retaining bolt to 108 N´m
(80 ft. lbs.) torque.
(4) Install the serpentine drive belt (Refer to 7 -
COOLING/ACCESSORY DRIVE/DRIVE BELTS -
INSTALLATION) and fan shroud.
(5) Connect negative cable to battery.
STRUCTURAL SUPPORT
REMOVAL
The engine bending braces are used to add
strength to the powertrain and to address some
minor NVH concerns.
Fig. 68 Compression Ring Installation
1 - COMPRESSION RING
2 - RING EXPANDER RECOMMENDED
Fig. 69 Ring Gap Orientation
1 - TOP COMPRESSION RING
2 - BOTTOM COMPRESSION RING
3 - TOP OIL CONTROL RAIL
4 - OIL RAIL SPACER
5 - BOTTOM OIL CONTROL RAIL
6 - IMAGINARY LINE PARALLEL TO PISTON PIN
7 - IMAGINARY LINE THROUGH CENTER OF PISTON SKIRT
Fig. 70 Vibration Damper Removal Tool 7697
1 - VIBRATION DAMPER REMOVAL TOOL
2 - WRENCH
WJENGINE - 4.0L 9 - 49
PISTON RINGS (Continued)

INSTALLATION
A gear-type oil pump is mounted at the underside
of the cylinder block opposite the No.4 main bearing.
(1) Install the oil pump on the cylinder block using
a replacement gasket. Tighten the bolts to 23 N´m
(17 ft. lbs.) torque.
(2) Install the oil pan (Refer to 9 - ENGINE/LU-
BRICATION/OIL PAN - INSTALLATION).
(3) Fill the oil pan with oil to the specified level.
INTAKE MANIFOLD
DESCRIPTION
The intake manifold (Fig. 83) is made of cast alu-
minum and uses eleven bolts to mount to the cylin-
der head. This mounting style improves sealing and
reduces the chance of leaks.
DIAGNOSIS AND TESTING - INTAKE
MANIFOLD LEAKAGE
An intake manifold air leak is characterized by
lower than normal manifold vacuum. Also, one or
more cylinders may not be functioning.
WARNING: USE EXTREME CAUTION WHEN THE
ENGINE IS OPERATING. DO NOT STAND IN A
DIRECT LINE WITH THE FAN. DO NOT PUT YOUR
HANDS NEAR THE PULLEYS, BELTS OR THE FAN.
DO NOT WEAR LOOSE CLOTHING.
(1) Start the engine.
(2) Spray a small stream of water at the suspected
leak area.
(3) If a change in RPM is observed the area of the
suspected leak has been found.
(4) Repair as required.
REMOVAL
NOTE: THE ENGINE INTAKE AND EXHAUST MANI-
FOLD MUST BE REMOVED AND INSTALLED
TOGETHER. THE MANIFOLDS USE A COMMON
GASKET AT THE CYLINDER HEAD.
(1) Disconnect the battery negative cable.
(2) Remove air cleaner inlet hose from the resona-
tor assembly.
(3) Remove the air cleaner assembly.
(4) Remove the throttle cable, vehicle speed control
cable (if equipped) and the transmission line pres-
sure cable (Refer to 21 - TRANSMISSION/TRANS-
AXLE/AUTOMATIC - AW4/THROTTLE VALVE
CABLE - REMOVAL).
(5) Disconnect the following electrical connections
and secure their harness out of the way:
²Throttle Position Sensor
²Idle Air Control Motor
²Coolant Temperature Sensor (at thermostat
housing)
²Intake Air Temperature Sensor
²Oxygen Sensor
²Crank Position Sensor
²Six (6) Fuel Injector Connectors
²Manifold Absolute Pressure (MAP) Sensor.
(6) Disconnect HVAC, and Brake Booster vacuum
supply hoses at the intake manifold.
(7) Perform the fuel pressure release procedure.
(Refer to 14 - FUEL SYSTEM/FUEL DELIVERY -
STANDARD PROCEDURE).
(8) Disconnect and remove the fuel system supply
line from the fuel rail assembly.
(9) Remove the accessory drive belt (Refer to 7 -
COOLING/ACCESSORY DRIVE/DRIVE BELTS -
REMOVAL).
(10) Remove the power steering pump from the
intake manifold and set aside.
(11) Raise the vehicle.
(12) Disconnect the exhaust pipes from the engine
exhaust manifolds.
(13) Lower the vehicle.
(14) Remove the intake manifold and exhaust
manifold bolts and manifolds (Fig. 84).
INSTALLATION
If the manifold is being replaced, ensure all the fit-
ting, etc. are transferred to the replacement mani-
fold.
(1) Install a new engine exhaust/intake manifold
gasket over the alignment dowels on the cylinder
head.
(2) Position the engine exhaust manifolds to the
cylinder head. Install fastener Number 3 and finger
tighten at this time (Fig. 84).
Fig. 83 Intake Manifold 4.0L Engine
WJENGINE - 4.0L 9 - 57
OIL PUMP (Continued)