1988 JEEP CHEROKEE ESP

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Page 1097 of 1378

JEEP CHEROKEE 1988 Service Repair Manual (1) - Require replacement of units where dents restrict shock
or strut piston rod movement. If dents dont restrict
movement, no service is suggested or required. Especially
critical

(1) - Require replacement of units where dents restrict shock
or strut piston rod movement. If dents don't restrict
movement, no service is suggested or required. Especially
critical on mono-tube shocks.
( 2) - This condition can lead to damage of the piston rod,
which, in turn, causes premature piston rod seal wear.
( 3) - Only required if replacing cartridge.
( 4) - CAUTION: If the strut cartridge has been replaced previously,
the oil on the strut housing may be filler oil. The
technician must identify the source of the oil.
( 5) - If noise is isolated to shock or strut, suggest
replacement.
( 6) - Although shocks or struts may have contributed to tire
cupping, an inspection is needed of the entire suspension
system. If the shock or strut is found to be contributing
to the tire cupping, require replacement.
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SPINDLES
SPINDLE INSPECTION\
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Condition Code Procedure
Attaching hardware
broken ................. A ... Require replacement of broken
part.
Attaching hardware
loose .................. A ... Require repair or replacement
of loose part.
Attaching hardware
missing ................ C .. Require replacement of missing
part.
Attaching hardware
threads damaged ........ A ... Require repair or replacement
of part with damaged threads.
Attaching hardware
threads stripped
(threads missing) ...... A ..... Require replacement of part
with stripped threads.
Bent .................... B ............ Require replacement.
Broken .................. A ............ Require replacement.
Race seat area
undersized ............. B ............ Require replacement.
Scored .................. A .. Require repair or replacement.
Threads damaged ......... A .. Require repair or replacement.
Threads stripped (threads
missing) ............... A ............ Require replacement.
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SPRINGS - COIL, LEAF AND TORSION BAR
When springs are replaced, it is suggested, but not required,
that both springs on an axle be replaced to maintain equal height from
side to side and to provide a balanced ride and proper handling.
When variable rate springs are installed in place of
conventional coil springs, they must be installed in axle sets to
ensure proper handling, uniform ride, and proper chassis height.
Erroneous height measurements may result from: improper tire
inflation, non-standard tire or wheel size, and heavy load in vehicle
or trunk.
SPRING (COIL, LEAF AND TORSION BAR) INSPECTION

Page 1102 of 1378

JEEP CHEROKEE 1988 Service Repair Manual piston rod movement. If dents dont restrict movement, no
service is suggested or required. Especially critical on
mono-tube dampers.
(2) - This condition can lead to damage of the p

piston rod movement. If dents don't restrict movement, no
service is suggested or required. Especially critical on
mono-tube dampers.
(2) - This condition can lead to damage of the piston rod,
which, in turn, causes premature piston rod seal wear.
( 3) - If noise is isolated to damper, suggest replacement.
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STEERING GEARS (EXCEPT RACK AND PINION)
If diagnosis has determined that complete disassembly is
necessary to determine the extent of the system failure, the
suggestion may be made to rebuild or replace the power steering pump.
Repair or replacement of the following components may be required, if
performed as part of a power steering pump overhaul or rebuild service
to meet a minimum rebuild standard.
STEERING GEAR (EXCEPT RACK AND PINION) INSPECTION
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Condition Code Procedure
Attaching hardware
broken ................. A .. Require replacement of broken
part.
Attaching hardware
loose .................. A .. Require repair or replacement
of loose part.
Attaching hardware
missing ................ C ......... Require replacement of
missing part.
Attaching hardware
threads damaged ........ A .. Require repair or replacement
of part with damaged threads.
Attaching hardware
threads stripped
(threads missing) ...... A .... Require replacement of part
with stripped threads.
Binding ................. A ... Require repair or replacement
Flex coupler binding .... A ... Require repair or replacement
of coupler.
Flex coupler loose ...... A ... Require repair or replacement
of coupler.
Flex coupler
missing parts .......... A ... Require repair or replacement
of coupler.
Flex coupler
soft/spongy ............ A . Require replacement of coupler.
Flex coupler torn ....... A . Require replacement of coupler.
Fluid contaminated ...... B ........ ( 1) Require flushing and
refilling of the system.
Gasket leaking .......... A ... Require repair or replacement
of gasket.
Housing leaking ......... A ............ Require replacement.
Hydraulic fittings
leaking ................ A ... Require repair or replacement
of fittings.
Inadequate power assist . A .......... ( 2) Further inspection
required.
See note below.
Lash exceeds
manufacturer's
specifications .......... B .. Require repair or replacement.
Seal leaking ............ A ... Require repair or replacement

Page 1132 of 1378

JEEP CHEROKEE 1988 Service Repair Manual TIE ROD ENDS (INNER AND OUTER)
TRACK BARS
TRAILING ARMS
WHEEL BEARINGS, RACES AND SEALS
Wheel Alignment
WHEEL ALIGNMENT
Wheels and

TIE ROD ENDS (INNER AND OUTER)
TRACK BARS
TRAILING ARMS
WHEEL BEARINGS, RACES AND SEALS
Wheel Alignment
WHEEL ALIGNMENT
Wheels and Tires
TIRES
VALVE STEMS
WHEEL ATTACHMENT HARDWARE
WHEELS (RIMS)
MOTORIST ASSURANCE PROGRAM (MAP)
OVERVIEW
The Motorist Assurance Program is the consumer outreach
effort of the Automotive Maintenance and Repair Association, Inc.
(AMRA). Participation in the Motorist Assurance Program is drawn from
retailers, suppliers, independent repair facilities, vehicle
manufacturers and industry associations.
Our organization's mission is to strengthen the relationship
between the consumer and the auto repair industry. We produce
materials that give motorists the information and encouragement to
take greater responsibility for their vehicles-through proper,
manufacturer-recommended, maintenance. We encourage participating
service and repair shops (including franchisees and dealers) to adopt
1) a Pledge of Assurance to their Customers and 2) the Motorist
Assurance Program Standards of Service. All participating service
providers have agreed to subscribe to this Pledge and to adhere to the
promulgated Standards of Service demonstrating to their customers that
they are serious about customer satisfaction.
These Standards of Service require that an inspection of the
vehicle's (problem) system be made and the results communicated to the\
customer according to industry standards. Given that the industry did
not have such standards, the Motorist Assurance Program successfully
promulgated industry inspection communication standards in 1994-95 for
the following systems: Exhaust, Brakes, ABS, Steering and Suspension,
Engine Maintenance and Performance, HVAC, and Electrical Systems.
Further, revisions to all of these inspection communication standards
are continually re-published. In addition to these, standards for
Drive Train and Transmissions have recently been promulgated.
Participating shops utilize these Uniform Inspection & Communication
Standards as part of the inspection process and for communicating
their findings to their customers.
The Motorist Assurance Program continues to work
cooperatively and proactively with government agencies and consumer
groups toward solutions that both benefit the customer and are
mutually acceptable to both regulators and industry. We maintain the
belief that industry must retain control over how we conduct our
business, and we must be viewed as part of the solution and not part
of the problem. Meetings with state and other government officials
(and their representatives), concerned with auto repair and/or
consumer protection, are conducted. Feedback from these sessions is
brought back to the association, and the program adjusted as needed.
To assure auto repair customers recourse if they were not
satisfied with a repair transaction, the Motorist Assurance Program
offers mediation and arbitration through MAP/BBB-CARE and other non-

Page 1158 of 1378

Page 1163 of 1378

Page 1268 of 1378

JEEP CHEROKEE 1988 Service Repair Manual In certain conditions, the pitch of the exhaust gases may
sound like gear whine. At other times, it may be mistaken for a wheel
bearing rumble.
Tires, especially radial and snow, can

In certain conditions, the pitch of the exhaust gases may
sound like gear whine. At other times, it may be mistaken for a wheel
bearing rumble.
Tires, especially radial and snow, can have a high-pitched
tread whine or roar, similar to gear noise. Also, some non-standard
tires with an unusual tread construction may emit a roar or whine.
Defective CV/universal joints may cause clicking noises or
excessive driveline play that can be improperly diagnosed as drive
axle problems.
Trim and moldings also can cause a whistling or whining
noise. Ensure none of these components are causing the noise before
disassembling the drive axle.
Gear Noise
A "howling" or "whining" noise from the ring and pinion gear
can be caused by an improper gear pattern, gear damage, or improper
bearing preload. It can occur at various speeds and driving
conditions, or it can be continuous.
Before disassembling axle to diagnose and correct gear
noise, make sure that tires, exhaust, and vehicle trim have been
checked as possible causes.
Chuckle
This is a particular rattling noise that sounds like a stick
against the spokes of a spinning bicycle wheel. It occurs while
decelerating from 40 MPH and usually can be heard until vehicle comes
to a complete stop. The frequency varies with the speed of the
vehicle.
A chuckle that occurs on the driving phase is usually caused
by excessive clearance due to differential gear wear, or by a damaged
tooth on the coast side of the pinion or ring gear. Even a very small
tooth nick or a ridge on the edge of a gear tooth is enough the cause
the noise.
This condition can be corrected simply by cleaning the gear
tooth nick or ridge with a small grinding wheel. If either gear is
damaged or scored badly, the gear set must be replaced. If metal has
broken loose, the carrier and housing must be cleaned to remove
particles that could cause damage.
Knock
This is very similar to a chuckle, though it may be louder,
and occur on acceleration or deceleration. Knock can be caused by a
gear tooth that is damaged on the drive side of the ring and pinion
gears. Ring gear bolts that are hitting the carrier casting can cause
knock. Knock can also be due to excessive end play in the axle shafts.
Clunk
Clunk is a metallic noise heard when an automatic
transmission is engaged in Reverse or Drive, or when throttle is
applied or released. It is caused by backlash somewhere in the
driveline, but not necessarily in the axle. To determine whether
driveline clunk is caused by the axle, check the total axle backlash
as follows:
1) Raise vehicle on a frame or twinpost hoist so that drive
wheels are free. Clamp a bar between axle companion flange and a part
of the frame or body so that flange cannot move.
2) On conventional drive axles, lock the left wheel to keep
it from turning. On all models, turn the right wheel slowly until it
is felt to be in Drive condition. Hold a chalk marker on side of tire
about 12" from center of wheel. Turn wheel in the opposite direction
until it is again felt to be in Drive condition.
3) Measure the length of the chalk mark, which is the total

Page 1319 of 1378

JEEP CHEROKEE 1988 Service Repair Manual full load. The Kent-Moore J-39021 is such a tool, though there are
others. The Kent-Moore costs around $240 at the time of this writing
and works on many different manufacturers systems.
The

full load. The Kent-Moore J-39021 is such a tool, though there are
others. The Kent-Moore costs around $240 at the time of this writing
and works on many different manufacturer's systems.
The second method is to use a lab scope. Remember, a lab
scope allows you to see the regular operation of a circuit in real
time. If an injector is having an short or intermittent short, the lab
scope will show it.
Checking Available Voltage At the Injector
Verifying a fuel injector has the proper voltage to operate
correctly is good diagnostic technique. Finding an open circuit on the
feed circuit like a broken wire or connector is an accurate check with
a DVOM. Unfortunately, finding an intermittent or excessive resistance
problem with a DVOM is unreliable.
Let's explore this drawback. Remember that a voltage drop due
to excessive resistance will only occur when a circuit is operating?
Since the injector circuit is only operating for a few milliseconds at
a time, a DVOM will only see a potential fault for a few milliseconds.
The remaining 90+% of the time the unloaded injector circuit will show
normal battery voltage.
Since DVOMs update their display roughly two to five times a
second, all measurements in between are averaged. Because a potential
voltage drop is visible for such a small amount of time, it gets
"averaged out", causing you to miss it.
Only a DVOM that has a "min-max" function that checks EVERY
MILLISECOND will catch this fault consistently (if used in that mode).\
The Fluke 87 among others has this capability.
A "min-max" DVOM with a lower frequency of checking (100
millisecond) can miss the fault because it will probably check when
the injector is not on. This is especially true with current
controlled driver circuits. The Fluke 88, among others fall into this
category.
Outside of using a Fluke 87 (or equivalent) in the 1 mS "min-\
max" mode, the only way to catch a voltage drop fault is with a lab
scope. You will be able to see a voltage drop as it happens.
One final note. It is important to be aware that an injector
circuit with a solenoid resistor will always show a voltage drop when
the circuit is energized. This is somewhat obvious and normal; it is a
designed-in voltage drop. What can be unexpected is what we already
covered--a voltage drop disappears when the circuit is unloaded. The
unloaded injector circuit will show normal battery voltage at the
injector. Remember this and do not get confused.
Checking Injector On-Time With Built-In Function
Several DVOMs have a feature that allows them to measure
injector on-time (mS pulse width). While they are accurate and fast to\
hookup, they have three limitations you should be aware of:
* They only work on voltage controlled injector drivers (e.g
"Saturated Switch"), NOT on current controlled injector
drivers (e.g. "Peak & Hold").
* A few unusual conditions can cause inaccurate readings.
* Varying engine speeds can result in inaccurate readings.
Regarding the first limitation, DVOMs need a well-defined
injector pulse in order to determine when the injector turns ON and
OFF. Voltage controlled drivers provide this because of their simple
switch-like operation. They completely close the circuit for the
entire duration of the pulse. This is easy for the DVOM to interpret.
The other type of driver, the current controlled type, start
off well by completely closing the circuit (until the injector pintle
opens), but then they throttle back the voltage/current for the
duration of the pulse. The DVOM understands the beginning of the pulse

Page 1321 of 1378

JEEP CHEROKEE 1988 Service Repair Manual severe weakness that we will look at later). If an injector has a
fault where it occasionally skips a pulse, the meter registers it and
the reading changes accordingly.
Lets go back to figur

severe weakness that we will look at later). If an injector has a
fault where it occasionally skips a pulse, the meter registers it and
the reading changes accordingly.
Let's go back to figuring out dwell/duty readings by using
injector on-time specification. This is not generally practical, but
we will cover it for completeness. You NEED to know three things:
* Injector mS on-time specification.
* Engine RPM when specification is valid.
* How many times the injectors fire per crankshaft revolution.
The first two are self-explanatory. The last one may require
some research into whether it is a bank-fire type that injects every
360
of crankshaft rotation, a bank-fire that injects every 720, or
an SFI that injects every 720. Many manufacturers do not release this
data so you may have to figure it out yourself with a frequency meter.
Here are the four complete steps to convert millisecond on-
time:
1) Determine the injector pulse width and RPM it was obtained
at. Let's say the specification is for one millisecond of on-time at a
hot idle of 600 RPM.
2) Determine injector firing method for the complete 4 stroke
cycle. Let's say this is a 360
bank-fired, meaning an injector fires
each and every crankshaft revolution.
3) Determine how many times the injector will fire at the
specified engine speed (600 RPM) in a fixed time period. We will use
100 milliseconds because it is easy to use.
Six hundred crankshaft Revolutions Per Minute (RPM) divided
by 60 seconds equals 10 revolutions per second.
Multiplying 10 times .100 yields one; the crankshaft turns
one time in 100 milliseconds. With exactly one crankshaft rotation in
100 milliseconds, we know that the injector fires exactly one time.
4) Determine the ratio of injector on-time vs. off-time in
the fixed time period, then figure duty cycle and/or dwell. The
injector fires one time for a total of one millisecond in any given
100 millisecond period.
One hundred minus one equals 99. We have a 99% duty cycle. If
we wanted to know the dwell (on 6 cylinder scale), multiple 99% times
.6; this equals 59.4
dwell.
Weaknesses of Dwell/Duty Meter
The weaknesses are significant. First, there is no one-to-one
correspondence to actual mS on-time. No manufacturer releases
dwell/duty data, and it is time-consuming to convert the mS on-time
readings. Besides, there can be a large degree of error because the
conversion forces you to assume that the injector(s) are always firing\
at the same rate for the same period of time. This can be a dangerous
assumption.
Second, all level of detail is lost in the averaging process.
This is the primary weakness. You cannot see the details you need to
make a confident diagnosis.
Here is one example. Imagine a vehicle that has a faulty
injector driver that occasionally skips an injector pulse. Every
skipped pulse means that that cylinder does not fire, thus unburned O2
gets pushed into the exhaust and passes the O2 sensor. The O2 sensor
indicates lean, so the computer fattens up the mixture to compensate
for the supposed "lean" condition.
A connected dwell/duty meter would see the fattened pulse
width but would also see the skipped pulses. It would tally both and
likely come back with a reading that indicated the "pulse width" was
within specification because the rich mixture and missing pulses
offset each other.
This situation is not a far-fetched scenario. Some early GM

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