1988 JEEP CHEROKEE Service Repair Manual

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2.5 L 4 -C YL - V IN [ H ]

1 988 J e ep C hero ke e
1988 CHRYSLER MOTORS ENGINES
2.5L 4-Cylinder
Jeep: Cherokee, Comanche, Wagoneer, Wrangler
ENGINE CODING
ENGINE IDENTIFICATION
NOTE: For engine repair procedures not covered in this article,
see ENGINE OVERHAUL PROCEDURES - GENERAL INFORMATION article
in the GENERAL INFORMATION section.
The Vehicle Identification Number (VIN) is located on the
upper left side of dash, visible through windshield. The fourth
character of the VIN identifies the engine size. The tenth character
identifies the model year.
ENGINE IDENTIFICATION CODES TABLE









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Application VIN Code
2.5L 4-Cylinder TBI .................................... H









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SPECIAL ENGINE MARKS
Some engines are produced at the factory with oversize or
undersize components. These engines are identified by a letter code
stamped between ignition coil and distributor. Letters are decoded as
follows:
* "B" indicates all cylinder bores .010" (.25 mm) oversize.
* "C" indicates all camshaft bearing bores .010" (.25 mm)
oversize.
* "M" indicates all main bearing journals .010" (.25 mm)
undersize.
* "P" indicates all connecting rod journals .010" (.25 mm)
undersize.
REMOVAL & INSTALLATION
ENGINE REMOVAL
See ENGINE REMOVAL article.
INTAKE & EXHAUST MANIFOLDS
NOTE: Throttle body removal is necessary prior to manifold
removal. Throttle body can be separated from the manifold
and secured in a designated area with vacuum hoses attached.
Removal
1) Disconnect negative battery cable. Remove air cleaner, EGR
pipe and PCV hose. Disconnect and mark all vacuum hoses and electrical
connections. Drain cooling system.
2) Remove coolant hoses from intake manifold. Remove A/C
compressor and power steering pump and mounting bracket (if equipped).\

Disconnect throttle valve linkage on A/T models.
3) Remove coolant temperature sensor wire. Disconnect
throttle cable at bellcrank. Remove intake manifold bolts. Remove
intake manifold.
4) If exhaust manifold requires removal, raise and support
vehicle. Disconnect exhaust pipe. Remove oxygen sensor wire and remove
sensor. Remove manifold-to-cylinder head bolts. Remove exhaust
manifold.
Installation
1) Ensure all gasket surfaces are clean. Install manifolds
and gasket on cylinder head. Start all bolts and finger tighten.
Tighten bolts in proper sequence. See Fig. 1. Tighten bolts to
specification. See TORQUE SPECIFICATIONS table.
2) Clean oxygen sensor threads. Apply anti-seize on oxygen
sensor threads prior to installation. Install sensor and tighten to
specification. Reverse removal procedures to complete installation.
Fill and purge cooling system. See COOLING SYSTEM AIR PURGE under
ENGINE COOLING.
Fig. 1: Manifold Bolt Tightening Sequence
CYLINDER HEAD
Removal
1) Disconnect negative battery cable. Drain cooling system.
Remove air cleaner. Remove intake and exhaust manifolds. See INTAKE &
EXHAUST MANIFOLDS.
2) Disconnect and mark all hoses and electrical connections
at cylinder head. Disconnect and mark spark plug wires. Remove spark
plugs. Remove valve cover bolts.

3) Remove rocker arms and push rods. See ROCKER ARMS &
BRIDGE under VALVES. Remove cylinder head bolts. Remove cylinder head.
Inspection
Inspect cylinder head for cracks or damage. Using
straightedge, check cylinder head for warpage in several areas. Repair
or replace cylinder head if warpage exceeds .002" (.05 mm) per each 6"\
(152 mm) or damage exists.
Installation
1) Ensure all gasket surfaces are clean. Clean carbon from
combustion chambers and tops of pistons. Apply sealant to both sides
of new cylinder head gasket. Install new gasket with the word "TOP"
upward. Ensure all holes are aligned.
2) Install cylinder head. Apply sealing compound to threads
of cylinder head bolt No. 8 prior to installation. See Fig. 2. Install
head bolts. Tighten all bolts in sequence (except No. 8) to 110 ft.
lbs. (149 N.m). Tighten No. 8 head bolt to 100 ft. lbs. (136 N.m). S\
ee
Fig. 2 .
3) Reverse removal procedures for remaining components. When
installing valve cover, use RTV sealant between cover and head.
Tighten bolts to specification.
4) Fill cooling system with temperature sending unit removed.
Allow trapped air to escape, then install sending unit. Refill and
purge cooling system. See COOLING SYSTEM AIR PURGE under ENGINE
COOLING.
Fig. 2: Cylinder Head Bolt Tightening Sequence
VALVES
Valve Arrangement
E-I-I-E-E-I-I-E (Front-to-rear).
Valve Guides
Valve guides are not replaceable. If clearance is excessive,
valve guides must be reamed to accommodate oversized stem valves.
ROCKER ARMS & BRIDGE

Removal
1) Remove PCV valve hose at valve cover. Remove valve cover
bolts. Using a razor knife, cut RTV sealant along valve cover. Pry
upward on valve cover in areas marked "PRY HERE" near bolt hole areas.
2) Remove valve cover. Alternately loosen each rocker arm
bolt one turn at a time. Remove rocker arm assemblies and push rods.
Mark components for reassembly. Components must be installed in
original location.
Installation
Reverse removal procedures. Install rocker arm components in
original location. Tighten bolts to specification. Apply RTV sealant
on valve cover prior to installation.
VALVE SPRINGS
Valve springs can be removed without removing cylinder head.
Valve Spring Installed Height
Information not available from manufacturer.
HYDRAULIC VALVE LIFTERS
Removal
Remove rocker arms and push rods. See ROCKER ARMS & BRIDGE.
Using Lifter Remover/Installer (J-21884), remove lifter through push
rod openings of cylinder head. Mark lifter location for reassembly
reference. Replace lifters as an assembly if damaged. Internal
components cannot be interchanged.
Inspection
Inspect lifter and camshaft mating surfaces for wear. Check
cylinder block lifter bore diameter. Lifter bore diameter should be
within .9055-.9065" (22.999-23.025 mm). Replace parts as necessary.
Installation
Soak lifter assembly in engine oil supplement prior to
installation. Reverse removal procedures for installation. Install
lifter in original location.
ENGINE FRONT COVER
Removal
1) Disconnect negative battery cable. Remove drive belts, fan
and hub assembly. Remove pulley from vibration damper. Remove
vibration damper retaining bolt and washer.
2) Using Puller (J-21719-01), remove vibration damper and
key. Remove oil pan-to-front cover bolts. Remove cover-to-block
retaining bolts. Remove front cover.
3) Cut oil pan gasket even with face of cylinder block.
Remove gasket from oil pan. Pry crankshaft oil seal from cover.
Installation
1) Ensure all gasket surfaces are clean. Ensure oil slinger
is installed on crankshaft. Apply sealing compound on both sides of
front cover gasket. Install gasket on cylinder block. Replace front
section of oil pan seal with similar section fabricated from new seal.
2) Coat seal with RTV sealant and place in position. Apply
sealant to the joint area of oil pan and cylinder block. Place front
cover on cylinder block. Place Front Cover Seal Installer (J-22248) in\
front cover seal area.
3) Install all retaining bolts. Tighten bolts to

specification. Install front cover oil seal. See FRONT COVER OIL SEAL
Remove front cover seal installer.
4) Reverse removal procedures. Lubricate vibration damper
retaining bolt with oil prior to installation. Tighten bolts to
specification.
FRONT COVER OIL SEAL
Removal & Installation
1) Remove vibration damper. Using Seal Remover (J-9256),
remove seal from front cover. Position new seal on Front Cover Seal
Installer (J-22248) with lip facing outward.
2) Apply sealant to seal outer diameter. Lightly coat
crankshaft with oil. Place front cover seal installer on front of
crankshaft. Tap seal into front cover. Remove seal installer. Lightly
coat seal contact area of vibration damper with oil.
3) Install key in crankshaft (if removed). Install vibration\
damper. Lubricate vibration damper bolt with oil. Install retaining
bolt and washer. Tighten to specification.
CAMSHAFT & TIMING GEAR
Removal
1) Drain cooling system. Remove radiator. Remove engine front
cover. See ENGINE FRONT COVER. Remove distributor. Remove fuel pump
(if equipped with mechanical pump). Remove rocker arms and pushrods.
See ROCKER ARMS & BRIDGE under VALVES.
2) Remove valve lifters. Mark lifters for location. Remove
crankshaft oil slinger. Pull chain tensioner block toward tensioner
lever to compress spring. Hold block and move tensioner lever to lock
position. See Fig. 3.
3) Rotate crankshaft and align timing marks on crankshaft and
camshaft gears. Remove camshaft gear retaining bolt. Remove gears and
timing chain. Remove camshaft.
Fig. 3: Location of Chain Tensioner Lock
Courtesy of Chrysler Motors.
Inspection
Inspect camshaft for flaking, lobe wear or worn bearing

journals. Replace if not within specification. See ENGINE
SPECIFICATIONS tables.
Installation
1) Lubricate camshaft and install. Avoid damage to camshaft
bearings. Install timing gears and timing chain. Rotate crankshaft and
camshaft so timing marks are aligned. See Fig. 4.
2) Install camshaft gear retaining bolt. Tighten to
specification. Install crankshaft oil slinger. Position chain tension
tensioner lever to the unlock (down) position. Reverse removal
procedures to complete installation.
CAUTION: Ensure chain tensioner is released prior to front cover
installation.
Fig. 4: Aligning Timing Marks
CAMSHAFT BEARINGS
Removal & Installation
Replace camshaft bearings using camshaft bearing remover/
installer. Ensure oil holes are aligned after installation.

OIL PAN
See OIL PAN REMOVAL article.
PISTON & ROD ASSEMBLY
NOTE: Mark piston cylinder location for reassembly reference.
Install pistons in original cylinder location.
Removal
1) Remove cylinder head. See CYLINDER HEAD under MANIFOLDS &
CYLINDER HEAD. Remove oil pan. See OIL PAN REMOVAL article. Remove
ridge or deposits from cylinder bore.
2) Mark connecting rod and piston for cylinder ID. Remove
bearing cap. Remove piston and rod assembly.
CAUTION: Arrow on top of piston must point toward front of engine.
Oil squirt holes in connecting rod must face camshaft when
installed.
Installation
1) Ensure ring end gap and side clearance are within
specification. See ENGINE SPECIFICATIONS tables. Install rings on
piston. Position ring end gaps at specified areas. See Fig. 5.
Fig. 5: Positioning Piston Ring Gaps
Ring gaps may vary 20 degrees from positions illustrated.
2) Lubricate piston assembly and cylinder block. Install
piston assembly. Arrow on top of piston must face toward front of

engine and connecting rod oil squirt hole should face camshaft side of
engine.
3) Install bearings. Check oil clearance and connecting rod
side play clearance. Reverse removal procedures for remaining
components. Tighten bolts to specification.
Fitting Pistons
1) Determine cylinder taper, wear and out-of-roundness and
piston clearance. For cylinder specifications, see CYLINDER, PISTON &
CONNECTING ROD SPECIFICATIONS table. If taper or out-of-roundness are
not within specification, hone or bore cylinders for installation of
new pistons.
2) Measure piston at right angle of the piston pin at the
center line of the pin. Compare reading to cylinder bore to determine
clearance. Mark fitted piston for cylinder location.
CYLINDER, PISTON & CONNECTING ROD SPECIFICATIONS TABLE









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Application In. (mm)
Connecting Rod
Crankshaft Bore .......... 2.2080-2.2085 (56.083-56.095)
Pin Bore ................... .9288-.9298 (23.591-23.616)
Cylinder Bore
Diameter ................. 3.8751-3.8775 (98.427-98.488)
Out-of-Round ................................ .001 (.02)
Taper ....................................... .001 (.02)
Piston Pin Bore Diameter ..... .9308-.9313 (23.642-23.655)
Piston Pin Diameter .......... .9304-.9309 (23.632-23.644)
Piston-to-Cylinder Clearance ..... .0009-.0017 (.022-.043)









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PISTON PIN REPLACEMENT
NOTE: Note direction of arrow on piston and oil squirt hole in
connecting rod prior to removal.
Removal
Position piston on Support (J-21872-1), Pin Pilot (J-21872-2\
)
and Driver (J-21872-3) on an arbor press. See Fig. 6. Press piston pin
from piston.
NOTE: Piston and pin must be at standard room temperature when
measuring fit. Piston pin should gravity-fall through the
piston at room temperature. Piston pin cannot be reused
after removal.
Inspection
Measure piston pin diameter, piston bore and connecting rod
bores. Replace components if not within specification. See CYLINDER,
PISTON & CONNECTING ROD SPECIFICATIONS table.
NOTE: Connecting rod must be positioned on the piston so the oil
squirt hole faces the camshaft side of the engine with
piston installed with arrow toward the front of the engine.
Installation
1) Insert pin pilot through piston and connecting rod. Place
assembly on support. Insert piston pin through the upper piston pin
bore and into connecting rod pin bore. See Fig. 6.