1988 JEEP CHEROKEE oil change

interchangeable. Inspect all components for wear. Note amount of wear
in lifter body-to-camshaft contact area. Surface must have smooth and
convex contact face. If wear is apparent, carefully inspect cam lobe.
Inspect push rod contact area and lifter body for scoring
or signs of wear. If body is scored, inspect lifter bore for damage
and lack of lubrication. On roller type lifters, inspect roller for
flaking, pitting, loss of needle bearings and roughness during
rotation.
Measure lifter body O.D. in several areas. Measure lifter
bore I.D. of cylinder block. Some models offer oversized lifters.
Replace lifter if damaged.
If lifter check valve is not operating, obstructions may be
preventing it from closing or valve spring may be broken. Clean or
replace components as necessary.
Check plunger operation. Plunger should drop to bottom of the
body by its own weight when assembled dry. If plunger is not free,
soak lifter in solvent to dissolve deposits.
Lifter leak-down test can be performed on lifter. Lifter
must be filled with special test oil. New lifters contain special test
oil. Using lifter leak-down tester, perform leak-down test following
manufacturer's instructions. If leak-down time is not within
specifications, replace lifter assembly.
Lifters should be soaked in clean engine oil several hours
prior to installation. Coat lifter base, roller (if equipped) and
lifter body with ample amount of Molykote or camshaft lubricant. See
Fig. 13. Install lifter in original location. Install remaining
components. Valve lash adjustment is not required on most hydraulic
lifters. Preload of hydraulic lifter is automatic. Some models may
require adjustment.
Mechanical Lifters
Lifter assemblies must be installed in original locations.
Remove rocker arm assembly and push rod. Mark components for location.
Some applications require intake manifold or lifter cover removal.
Remove lifter retainer plate (if used). To remove lifters, use lifter
remover or magnet.
Inspect push rod contact area and lifter body for scoring or
signs of wear. If body is scored, inspect lifter bore for damage and
lack of lubrication. Note amount of wear in lifter body-to-camshaft
contact area. Surface must have smooth and convex contact face. If
wear is apparent, carefully inspect cam lobe.
Coat lifter base, roller (if equipped) and lifter body with
ample amount of Molykote or camshaft lubricant. Install lifter in
original location. Install remaining components. Tighten bolts to
specification. Adjust valves. See VALVE ADJUSTMENT in this article.
PISTONS, CONNECTING RODS & BEARINGS
* PLEASE READ THIS FIRST *
NOTE: Always refer to appropriate engine overhaul article in the
ENGINES section for complete overhaul procedures and
specifications for the vehicle being repaired.
RIDGE REMOVAL
Ridge in cylinder wall must be removed prior to piston
removal. Failure to remove ridge prior to removing pistons will cause
piston damage in piston ring locations.
With the piston at bottom dead center, place a rag in the
bore to trap metal chips. Install ridge reamer in cylinder bore.
Adjust ridge reamer using manufacturer's instructions. Remove ridge

mounted on throttle body and senses angle of throttle blade opening.
A voltage signal of up to 5 volts at wide open throttle is
produced by TPS. Voltage varies with throttle angle changes. This
signal is transmitted to ECU where it is used to adjust air/fuel
ratio during acceleration, deceleration, idle, and wide open throttle
conditions.
A dual TPS is used on models with automatic transmissions.
This dual TPS not only provides ECU with input voltages but also
supplies automatic transmission control unit with input signals
relative to throttle position.
Knock Sensor
Knock sensor (detonation sensor) is located on lower left
side of cylinder block just above oil pan. Knock sensor picks up
detonation vibration from engine and converts it to an electrical
signal for use by ECU.
ECU uses this information to determine when a change in
ignition timing is required. Knock sensor allows for engine operation
on either "premium" unleaded or "regular" unleaded fuel.
When knock occurs, ECU retards ignition timing in one or
more cylinders until detonation is eliminated.
Speed Sensor
Speed sensor is secured by special shouldered bolts to
flywheel/drive plate housing. Speed sensor is nonadjustable and
preset at factory. Speed sensor senses TDC and engine speed by
detecting flywheel teeth as they pass pick-up coil during engine
operation. See Fig. 2.
Flywheel has a large trigger tooth and notch located 12
small teeth before each TDC position. When a small tooth and notch
pass the magnetic core in sensor, concentration and collapse of the
magnetic field created induces a small voltage spike into sensor
pick-up coil windings. These small voltage spikes are sent to ECU,
allowing ECU to count the teeth as they pass sensor.
When a large tooth and notch pass magnetic core in sensor,
increased concentration and collapse of the magnetic field induces a
higher voltage spike than smaller teeth. Higher spike indicates to
ECU that a piston will soon be at TDC position, 12 teeth later.
Ignition timing for cylinder is either advanced or retarded by ECU
based upon "sensor input".
Fig. 2: Speed Sensor Operation
Courtesy of Chrysler Motors.
Engine Switches
Several switches provide operating information to ECU. These

Coolant temperature sensor is installed in intake manifold
water jacket to provide coolant temperature input signal for ECU.
During cold engine operation, ECU will make mixture richer, make up
for fuel condensation in cold intake manifold, increase idle speed
during warm-up period, increase ignition advance and keep EGR system
inoperative until engine warms up.
THROTTLE POSITION SENSOR (TPS)
Throttle position sensor provides ECU with input signal, up
to about 5 volts, to indicate throttle position. This allows ECU to
control air/fuel mixture according to throttle position. TPS is
mounted on throttle body assembly.
WIDE OPEN THROTTLE (WOT) SWITCH
WOT switch provides an input signal to ECU when engine is at
wide open throttle. The ECU enriches air/fuel mixture. The WOT switch
is located on the side of throttle body.
CLOSED THROTTLE (IDLE) SWITCH
Idle switch is integral with ISA motor and provides voltage
signal to ECU. ECU will signal ISA motor to change throttle stop
angle in response to engine operating conditions.
UPSHIFT INDICATOR LIGHT
On vehicles equipped with a manual transmission, ECU
controls upshift indicator light. Indicator light is normally
illuminated when ignition is turned on without engine running.
Indicator light is turned off when engine is started.
Indicator light will be illuminated during engine operation
in response to engine load and speed. If transmission is not shifted,
ECU will turn light off after 3 to 5 seconds. A switch located on
transmission prevents indicator light from being illuminated when
transmission is shifted to highest gear.
ENGINE SPEED SENSOR
Engine speed sensor is attached to bellhousing. It senses
and counts teeth on flywheel gear ring as they pass during engine
operation. Signal from speed sensor provides ECU with engine speed
and crankshaft angle. On flywheel gear ring, large trigger tooth and
notch is located 90 degrees before each TDC point. Each trigger tooth
is followed by 12 smaller teeth and notches before TDC point is
reached.
As each of 12 small teeth and notches pass magnetic core in
speed sensor, concentration and collapse of magnetic field induces
slight voltage (spike) in sensor pick-up coil winding. See Fig. 2.
Larger trigger teeth and notches induce higher voltage (spike) in
sensor pick-up coil winding. These voltage spikes enable ECU to count
teeth as they pass speed sensor.
Higher voltage spike (from larger tooth and notch) indicates
to ECU that piston will be at TDC position after 12 smaller voltage
spikes have been counted. ECU will then either advance or retard
ignition timing depending upon remaining sensor inputs.

Fig. 3: Ignition Control Module Connector Identification
Courtesy of Chrysler Motors.
Terminal "B" of Connector No. 1 is grounded at the engine oil
dipstick bracket along with the ECU ground wire and Oxygen (O2) sensor\
ground.
The tachometer output signal wire of the ICM is connected to
Pin No. 1 of the "D1" Diagnostic connector. The wire is routed to the
diagnostic connector through a short section of the ECU harness, the
engine, and the instrument panel harness. This type of routing
eliminates any potential electrical interference from occurring in the
various ECU circuitry.
Ignition firing signals from ECU terminal "27" are
transmitted through terminal "B" of Connector No. 2 on the ICM. the
ignition signal from the ECU is received by the ICM in the form of a 5
volt square wave. As the leading edge of the wave contacts the
ignition circuitry in the ICM, the ICM charges the coil primary
windings.
When coil saturation occurs, the module circuitry opens the
primary windings to collapse the magnetic field in the windings. This
induces the coil secondary windings which is then transmitted to the
spark plug via the coil wire, distributor cap, and rotor.
MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR
The MAP sensor reacts to absolute pressure in the intake
manifold and provides an input signal to the ECU. As the engine load
changes, manifold pressure varies, which causes the MAP sensor
resistance to change, resulting in a different input voltage to the
ECU. The input voltage level supplies the ECU with information
relating to ambient barometric pressure during engine start-up or
regarding engine load while the engine is running. The ECU calculates
this information and adjusts the air-fuel mixture accordingly.
The MAP sensor is mounted under the hood on the firewall and
is connected to the throttle body with a vacuum hose. See Fig. 4.

Electronic Spark Timing (EST) is used on most computer
controlled systems. The Electronic Control Module (ECM) monitors
information from various engine sensors, computes desired spark
timing, and signals distributor for correct timing change. The HEI
distributor with EST does not have centrifugal advance weights,
springs, or a vacuum advance unit. See Figs. 2 and 3.
HEI & EST WITH ELECTRONIC SPARK CONTROL (ESC)
All fuel injected vehicles are equipped with Electronic Spark
Control (ESC). ESC systems contain a knock sensor mounted in the
engine block. A Blue wire connects the sensor to the ESC module. If
the sensor detects knock, it sends a signal to the module which, in
turn, signals the ECM. The ECM sends a signal to the distributor to
retard spark timing.
Fig. 2: Typical HEI/EST Distributor, Integral coil system shown.
Courtesy of General Motors Corp.
OPERATION

\003
IN STR UM EN T P A N EL - S TA N DAR D

1988 J e ep C hero ke e
1988 Switches & Instrument Panels
JEEP
DESCRIPTION & OPERATION
Instrument panel is composed of speedometer housing,
tachometer and instrument cluster gauges.
FUEL GAUGE
System consists of a fuel gauge, an in-tank sending unit, and
appropriate wiring. Fuel gauge is grounded through variable resistor
of sending unit. A float attached to a slide rheostat follows fuel
level and varying resistance increases or decreases indicator reading.
TEMPERATURE GAUGE
System consists of gauge and sending unit and appropriate
wiring. The gauge is grounded through variable resistor of sending
unit. Changes in coolant temperature vary resistance in sending unit,
increasing or decreasing indication on gauge.
VOLTMETER
The voltmeter indicates regulated voltage to provide an
indication of charging system's ability to maintain battery charge.
OIL PRESSURE GAUGE
The oil pressure gauge system consists of gauge and a
variable resistance sending unit. Gauge needle, attached to bi-
metallic strip, responds to temperature changes.
REMOVAL & INSTALLATION
INSTRUMENT CLUSTER
Removal & Installation
1) Disconnect negative battery cable. On models with cruise
control, reach behind instrument cluster and disconnect speedometer
cable from speed switch. See Fig. 1.
2) On models without cruise control, raise vehicle on hoist.
Disconnect speedometer cable from transfer case (or transmission) and
at frame rail bracket. Move speedometer cable forward and upward to
provide slack. Lower vehicle.
3) On all models, remove instrument panel bezel screws and
bezel. Remove screws attaching cigarette lighter and switch housings
to instrument panel. Move housings aside.
4) Remove screws attaching cluster to instrument panel and
carefully pull cluster and speedometer toward rear of vehicle.
Disconnect wiring harness connectors.
5) Squeeze speedometer cable locking tabs and disconnect
cable from speedometer. See Fig. 1. Remove instrument cluster. To
install, reverse removal procedure.

* Cold Climate Operation
* Towing Or Heavily Loading
* Severe Dust Conditions
* Sustained High Speed Operation
* Off-Road Driving
* Hot Weather, Stop-And-Go Driving
* Extensive Idling Conditions (Taxi Or Delivery Type Service)
Normal Service
* Driven More Than 10 Miles Daily
* No Severe Service Operating Conditions
CAMSHAFT TIMING BELT REPLACEMENT INFORMATION (TURBO-DIESEL)
CAUTION: Failure to replace a faulty camshaft timing belt may result
in serious engine damage.
The condition of camshaft drive belts should always be
checked on vehicles which have more than 50,000 miles. Although some
manufacturers do not recommend belt replacement at a specified
mileage, others require it at 60,000-100,000 miles. A camshaft drive
belt failure may cause extensive damage to internal engine components
on most engines, although some designs do not allow piston-to-valve
contact. These designs are often called "Free Wheeling".
Many manufacturers changed their maintenance and warranty
schedules in the mid-1980's to reflect timing belt inspection and/or
replacement at 50,000-60,000 miles. Most service interval schedules
reflect these changes.
Belts or components should be inspected and replaced if any
of the following conditions exist:
* Cracks Or Tears In Belt Surface
* Missing, Damaged, Cracked Or Rounded Teeth
* Oil Contamination
* Damaged Or Faulty Tensioners
* Incorrect Tension Adjustment
SERVICE LABOR TIMES
SERVICE LABOR TIMES TABLE (HOURS)








\









\









\









\









\









\









\



( 1) 30,000 60,000
Application Mile Service Mile Service
2.1L (Turbo Diesel)
Automatic Transmission ........... 4.3 ................ 4.5
Manual Transmission .............. 3.6 ................ 3.8
2.5L
Automatic Transmission ........... 5.6 ................ 3.5
Manual Transmission .............. 4.9 ................ 3.5
2.8L
Automatic Transmission ........... 5.8 ................ 3.7
Manual Transmission .............. 5.1 ................ 3.7
4.0L
Automatic Transmission ........... 5.7 ................ 3.6
Manual Transmission .............. 5.0 ................ 3.6
( 1) - Add .8 hr. for vehicles equipped with 4WD.









\









\









\









\









\









\









\



Brake Caliper Bushings ....... GE 661 or DOW 111 Silicone Grease
Caliper Slide Pins .......... GE 661 or DOW 111 Silicone Grease
Wheel Bearings ............ Multi-Purpose NLGI Grade 2EP, GC-LB
Drive Shaft U-Joints ...... Multi-Purpose NLGI Grade 2EP, GC-LB
Steering Linkage (4)( 5) ... Multi-Purpose NLGI Grade 2EP, GC-LB
Ball Joints ( 4)( 6) ........ Multi-Purpose NLGI Grade 2EP, GC-LB
Engine Oil Filter (Diesel) ( 7) .... AMC/Jeep (P/N 8983 002 656)
Weatherstrip ......................... Silicone Spray Lubricant
( 1) - SAE 10W-30 SH/CD is preferred.
( 2) - Add 2 Ozs. (59 ml) of Limited-Slip differential lubricant
additive when changing fluid.
( 3) - For vehicles operating under heavy-duty towing conditions,
use SAE 75W-140 Synthetic lube.
NOTE: Before using SAE 75W-140 Synthetic the old fluid must be
DRAINED and FLUSHED with clean mineral based (non-synthetic)
axle lubricant. Then refill with new synthetic lube.
( 4) - Use low pressure grease gun to prevent seal damage.
( 5) - Fill until lubricant squeezes out from the base of seals.
( 6) - Fill ball joint until seal starts to swell.
( 7) - Use of AMC/Jeep Oil Filter is RECOMMENDED.









\









\









\









\









\









\









\



FLUID CAPACITIES
FLUID CAPACITIES TABLE








\









\









\









\









\









\









\



Application Quantity ( 1)
A/C System R-12 Refrigerant Capacity ............... 36-40 Ozs.
Automatic Transmission
1984-86 (904 HD)
Fluid Change .............................. 4.0 Qts. (3.8L)
Overhaul (Dry Fill) ....................... 8.0 Qts. (7.6L)
1987-88
Fluid Change .............................. 4.0 Qts. (3.8L)
Overhaul (Dry Fill) ....................... 8.5 Qts. (8.0L)
Cooling System ( 2)
4-Cylinder ................................. 10.0 Qts. (9.5L)
6-Cylinder ................................ 12.0 Qts. (11.4L)
4-Cylinder Turbo Diesel (1985-87) ........... 9.0 Qts. (8.5L)
Engine Oil
4-Cylinder .................................. 4.0 Qts. (3.8L)
6-Cylinder .................................. 6.0 Qts. (5.7L)
4-Cylinder Turbo Diesel (1985-87) ........... 5.5 Qts. (8.5L)
Fuel Tank
Standard ................................. 13.5 Gals. (51.1L)
Optional ................................... 20 Gals. (75.7L)
Manual Transmission ( 3)
AX4 (AISIN) ................................. 7.4 Pts. (3.5L)
T4 (Borg-Warner) ............................ 3.9 Pts. (1.8L)
AX5 (AISIN) ................................. 7.0 Pts. (3.3L)
T5 (Borg-Warner) ............................ 4.5 Pts. (2.1L)
Transfer Case
1985-86
Selec-Trac (229 Full-Time) ................ 6.0 Pts. (2.8L)
Command-Trac (Part-Time 207) .............. 4.5 Pts. (2.1L)
1987
Selec-Trac ................................ 2.5 Pts. (1.2L)
Command-Trac .............................. 2.2 Pts. (1.0L)
1988
Selec-Trac ................................ 3.0 Pts. (1.4L)