1988 JEEP CHEROKEE engine

Dry or binding clutch Lubricate and align
pedal hub components
Floor mat interference Lay mat flat in proper
with pedal area
Dry or binding ball/fork Lubricate and align
pivots components
Faulty clutch cable Replace clutch cable









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Noisy Clutch Faulty interlock switch Replace interlock
Pedal switch
Self-adjuster ratchet Lubricate or replace
noise self-adjuster
Speed control interlock Lubricate or replace
switch interlock switch









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Clutch Pedal Binding clutch cable See CLUTCH article
Sticks Down
Springs weak in pressure Replace pressure plate
plate
Binding in clutch linkage Lubricate and free
linkage









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Noisy Dry release bearing Lubricate or replace
release bearing
Dry or worn pilot bearing Lubricate or replace
bearing
Worn input shaft bearing Replace bearing









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Transmission Weak springs in pressure Replace pressure plate
Click plate
Release fork loose on ball Replace release fork
stud and/or ball stud
Oil on clutch disc damper Replace clutch disc
Broken spring in slave Replace slave cylinder
cylinder









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DRIVE AXLE - NOISE DIAGNOSIS
Unrelated Noises
Some driveline trouble symptoms are also common to the
engine, transmission, wheel bearings, tires, and other parts of the
vehicle. Ensure cause of trouble actually is in the drive axle before
adjusting, repairing, or replacing any of its parts.
Non-Drive Axle Noises
A few conditions can sound just like drive axle noise and
have to be considered in pre-diagnosis. The 4 most common noises are
exhaust, tires, CV/universal joints and wheel trim rings.

axle backlash. If backlash is one inch or less, drive axle is not the
source of clunk noise.
Bearing Whine
Bearing whine is a high-pitched sound similar to a whistle.
It is usually caused by malfunctioning pinion bearings. Pinion
bearings operate at drive shaft speed. Roller wheel bearings may whine
in a similar manner if they run completely dry of lubricant. Bearing
noise will occur at all driving speeds. This distinguishes it from
gear whine, which usually comes and goes as speed changes.
Bearing Rumble
Bearing rumble sounds like marbles being tumbled. It is
usually caused by a malfunctioning wheel bearing. The lower pitch is
because the wheel bearing turns at only about 1/3 of drive shaft
speed.
Chatter On Turns
This is a condition where the entire front or rear of vehicle
vibrates when vehicle is moving. The vibration is plainly felt as well
as heard. Extra differential thrust washers installed during axle
repair can cause a condition of partial lock-up that creates this
chatter.
Axle Shaft Noise
Axle shaft noise is similar to gear noise and pinion bearing
whine. Axle shaft bearing noise will normally distinguish itself from
gear noise by occurring in all driving modes (Drive, cruise, coast and
float), and will persist with transmission in Neutral while vehicle is
moving at problem speed.
If vehicle displays this noise condition, remove suspect
axle shafts, replace wheel seals and install a new set of bearings.
Re-evaluate vehicle for noise before removing any internal components.
Vibration
Vibration is a high-frequency trembling, shaking or grinding
condition (felt or heard) that may be constant or variable in level
and can occur during the total operating speed range of the vehicle.
The types of vibrations that can be felt in the vehicle can
be divided into 3 main groups:
* Vibrations of various unbalanced rotating parts of the
vehicle.
* Resonance vibrations of the body and frame structures caused
by rotating of unbalanced parts.
* Tip-in moans of resonance vibrations from stressed engine or
exhaust system mounts or driveline flexing modes.
DRIVE AXLE - RWD TROUBLE SHOOTING
NOTE: This is GENERAL information. This article is not intended
to be specific to any unique situation or individual vehicle
configuration. The purpose of this Trouble Shooting
information is to provide a list of common causes to
problem symptoms. For model-specific Trouble Shooting,
refer to SUBJECT, DIAGNOSTIC, or TESTING articles available
in the section(s) you are accessing. For definitions
of listed noises or sounds, see DRIVE AXLE - NOISE DIAGNOSIS
under POWERTRAIN.
DRIVE AXLE (RWD) TROUBLE SHOOTING









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CONDITION POSSIBLE CAUSE CORRECTION

Brakes dragging See BRAKES article








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Instability Low or uneven tire Inflate to proper
pressure pressure
Loose or worn wheel See FRONT SUSPENSION
bearings article
Loose or worn idler arm See FRONT SUSPENSION
bushing article
Loose or worn strut See FRONT SUSPENSION
bushings article
Incorrect front wheel See WHEEL ALIGNMENT
alignment article
Steering gear not See MANUAL STEERING
centered GEARS article
Springs or shock Check and replace if
necessary
Improper cross shaft See MANUAL STEERING
GEARS article









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POWER STEERING TROUBLE SHOOTING
NOTE: This is GENERAL information. This article is not intended
to be specific to any unique situation or individual vehicle
configuration. The purpose of this Trouble Shooting
information is to provide a list of common causes to
problem symptoms. For model-specific Trouble Shooting,
refer to SUBJECT, DIAGNOSTIC, or TESTING articles available
in the section(s) you are accessing.
BASIC POWER STEERING TROUBLE SHOOTING CHART









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CONDITION POSSIBLE CAUSE CORRECTION








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Rattle or Pressure hoses touching Adjust to proper
Chucking Noise engine parts clearance
Loose Pitman shaft Adjust or replace if
necessary
Tie rods ends or Pitman Tighten and check system
arm loose
Rack and pinion mounts Tighten all mounting
loose bolts
Free play in worm and See POWER STEERING GEAR
article
Loose sector shaft or See POWER STEERING GEAR
thrust bearing adjustment
Free play in pot coupling See STEERING COLUMN
article

Reaction ring sticking See POWER STEERING GEAR
in housing head article
Steering pump internal See POWER STEERING PUMP
leakage article
Steering gear-to-column See STEERING COLUMN
misalignment article
Lack of lubrication in Service front suspension
linkage
Lack of lubrication in Service front suspension
ball joints









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Increased Effort High internal pump leakage See POWER STEERING PUMP
When Turning article
Wheel Fast Power steering pump belt Adjust or replace if
Foaming, Milky slipping necessary
Power Steering
Fluid, Low Fluid Low fluid level Check and fill to
Level or Low proper level
Pressure
Engine idle speed to low Adjust to correct
setting
Air in pump fluid system See POWER STEERING PUMP
article
Pump output low See POWER STEERING PUMP
article
Steering gear See POWER STEERING GEAR
malfunctioning article









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Wheel Surges Low fluid level Check and fill to proper
or Jerks level
Loose fan belt Adjust or replace if
necessary
Insufficient pump See POWER STEERING PUMP
pressure article
Sticky flow control valve See POWER STEERING PUMP
article
Linkage hitting oil pan Replace bent components
at full turn









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Kick Back or Air in pump fluid system See POWER STEERING PUMP
Free Play article
Worn poppet valve in See POWER STEERING PUMP
steering gear article
Excessive over center See POWER STEERING GEAR
lash article
Thrust bearing out of See POWER STEERING GEAR
adjustment article

Free play in pot coupling See POWER STEERING PUMP
article
Steering gear coupling See POWER STEERING PUMP
loose on shaft article
Steering disc mounting Tighten or replace if
bolts loose necessary
Coupling loose on worm Tighten or replace if
shaft necessary
Improper sector shaft See POWER STEERING GEAR
adjustment article
Excessive worm piston See POWER STEERING GEAR
side play article
Damaged valve lever See POWER STEERING GEAR
article
Universal joint loose Tighten or replace if
necessary
Defective rotary valve See POWER STEERING GEAR
article









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No Power When Sticking flow control See POWER STEERING PUMP
Parking valve article
Insufficient pump See POWER STEERING PUMP
pressure output article
Excessive internal pump See POWER STEERING PUMP
leakage article
Excessive internal gear See POWER STEERING PUMP
leakage article
Flange rubs against gear See STEERING COLUMN
adjust plug article
Loose pump belt Adjust or replace if
necessary
Low fluid level Check and add proper
amount of fluid
Engine idle too low Adjust to correct
setting
Steering gear-to-column See STEERING COLUMN
misaligned article









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No Power, Left turn reaction seal See POWER STEERING GEAR
Left Turn "O" ring worn article
Left turn reaction seal See POWER STEERING GEAR
damaged/missing article
Cylinder head "O" ring See POWER STEERING PUMP
damaged article









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TU NE-U P - 4 -C YL

1988 J e ep C hero ke e
1988 Jeep 4 Tune-Up
TUNE-UP
All Models
IDENTIFICATION
ENGINE IDENTIFICATION
Engine can be identified by the 4th character of the Vehicle
Identification Number (VIN). The VIN is stamped on a plate attached to\
top left corner of instrument panel.
ENGINE CODES









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Engine Code
2.5L (150") TBI .................................................. H\









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TUNE-UP NOTES
NOTE: When performing tune-up procedures described in this
article, the following notes and precautions must be
followed.
Due to late changes and corrections, always refer to Emission
Control Label in engine compartment before attempting tune-up. If
manual and label differ, always use label specifications.
EPA High Altitude emission standards apply to vehicles sold
in certain areas outside California which have an elevation above 4000
feet.
When performing tune-up on vehicles equipped with catalytic
converter, do not allow or create an engine misfire in one or more
cylinders for an extended period of time. Damage to converter may
occur due to loading converter with unburned fuel.
TESTING
ENGINE COMPRESSION
Test compression with all spark plugs removed, throttle
plates and choke valve wide open and engine at normal operating
temperature. Crank engine through at least 5 compression strokes
before recording reading.
COMPRESSION SPECIFICATIONS









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Application Specification
Compression Ratio ............................................ 9.2:1
Compression Pressure ................ 155-185 psi (10.9-13.0 kg/cm
)
Max. Variation Between Cylinders ............... 30 psi (2.1 kg/cm)








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SPARK PLUGS
SPARK PLUG TYPE

Fig. 1: 2.5L Firing Order & Distributor Rotation
IGNITION TIMING
NOTE: No adjustment is possible on models with Renix ignition.
HOT (SLOW) IDLE RPM
NOTE: Adjust ISC motor plunger only after replacing ISC motor.
Idle Speed Control (ISC) Motor Plunger
1) Remove air cleaner, turn off A/C (if equipped) and warm
engine to normal operating temperature. Connect tachometer negative
lead to diagnostic connector terminal "D1-3" and positive lead to
connector terminal "D1-1". See Fig. 2. Turn ignition off. ISC plunger
should fully extend.

Fig. 2: TBI Diagnostic Connector & Terminal ID
Courtesy of Chrysler Motors.
2) With plunger extended, disconnect ISC motor electrical
connector. Start engine. Engine idle speed should be 3300-3700 RPM. If
not, turn plunger hex head to obtain 3500 RPM. See Fig. 3.
3) To fully retract ISC motor, hold closed throttle switch
plunger inward while opening throttle. Closed throttle switch plunger
should not touch throttle lever when throttle is closed. If this
occurs, check linkage and/or cable for binding.