1988 JEEP CHEROKEE 6 cylinder

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* D RIV ETR AIN S YSTE M S U NIF O RM IN SPEC TIO N G UID ELIN ES *
1988 Jeep Cherokee
GENERAL INFORMATION
Drivetrain/Transmission Motorist Assurance Program
Standards For Automotive Repair
All Makes and Models
INTRODUCTION TO MOTORIST ASSURANCE PROGRAM (MAP)
CONTENTS
OVERVIEW OF MOTORIST ASSURANCE PROGRAM
OVERVIEW OF SERVICE REQUIREMENTS & SUGGESTIONS
Drive/Power Train Assemblies
AUTOMATIC TRANSMISSION/TRANSAXLE ASSEMBLIES
DIFFERENTIAL AND FINAL DRIVE ASSEMBLIES
MANUAL TRANSMISSION/TRANSAXLE ASSEMBLIES
TRANSFER CASE ASSEMBLIES
Drive/Power Train Components
ACTUATORS (ELECTRICAL)
ACTUATORS (VACUUM)
AXLES
BEARINGS AND RACES
BELL CRANKS
BELL HOUSINGS
BUSHINGS (EXTERNAL)
CABLES (SPEEDOMETER)
CABLES (TV, DETENT AND SHIFT)
CARRIER BEARINGS
CLUTCH CABLES AND CABLE HOUSINGS
CLUTCH DISCS (MANUAL TRANSMISSION)
CLUTCH FORKS
CLUTCH LINKAGES (MECHANICAL)
CLUTCH MASTER CYLINDERS
CLUTCH PEDALS
CLUTCH PIVOTS
CLUTCH PRESSURE PLATES
CLUTCH RELEASE BEARINGS
CLUTCH SLAVE CYLINDERS (CONCENTRIC)
CLUTCH SLAVE CYLINDERS (CONVENTIONAL OR EXTERNAL)
COMPANION FLANGES
CONNECTORS
COOLER BYPASS VALVES
COOLER LINES
COOLERS
CV JOINTS
DIP STICK TUBES
DIP STICKS (FLUID LEVEL INDICATORS)
DOWEL PINS, GUIDES AND PILOT HOLES
DRIVE SHAFT FLANGES
DRIVE SHAFTS AND HALF SHAFTS
DUST BOOTS
ENGINE MOUNTS
EXCITER RINGS
FILLER TUBES
FILTERS AND SCREENS

CLUTCH LINKAGES (MECHANICAL)
See LINKAGES (EXTERNAL) .
CLUTCH MASTER CYLINDERS
CLUTCH MASTER CYLINDER INSPECTION








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Condition Code Procedure
Cover gasket distorted .. A .... Require replacement of cover
gasket.
Cover gasket gummy ...... A .... Require replacement of cover
gasket.
Cylinder leaking fluid
from rear of bore ...... A .. Require repair or replacement.
Cylinder leaking fluid
internally ............. A ............ Require replacement.
Dust boot missing ....... C ..... Require replacement of dust
boot.
Dust boot punctured ..... A ..... Require replacement of dust
boot.
Dust boot torn .......... A ..... Require replacement of dust
boot.
Fluid level incorrect ... B . Require fluid level adjustment.
Housing damaged, affecting
performance ............ A .. Require repair or replacement.
Master cylinder has
residue in reservoir
(make parallel w/brakes
when they are done) .... 2 .......... ( 1) Further inspection
required.
Threads damaged ......... A ...... Require repair replacement
Threads stripped (threads
missing) ............... A ............ Require replacement.
( 1) - DO NOT replace master cylinder unless it exhibits
conditions listed for replacement. You may suggest fluid
change according to OEM service intervals.









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CLUTCH PEDALS
CLUTCH PEDAL INSPECTION








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Condition Code Procedure
Bent, affecting
performance ............ A .. Require repair or replacement.
Broken .................. A .. Require repair or replacement.
Pedal pad missing ....... C .......... Require replacement of
pedal pad.
Pivot bushings worn,
affecting performance .. A .... Require replacement of pivot
bushings.









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CLUTCH PIVOTS
CLUTCH PIVOT INSPECTION








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Condition Code Procedure
Bent .................... A ............ Require replacement.
Broken .................. A .. Require repair or replacement.
Cracked ................. A .. Require repair or replacement.
Threads damaged ......... A .. Require repair or replacement.
Threads stripped (threads
missing) ............... A ............ Require replacement.
Worn close to the end of
its useful life ........ 1 ............ Suggest replacement.
Worn, affecting
performance ............ A ............ Require replacement.









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CLUTCH PRESSURE PLATES
See PRESSURE PLATES .
CLUTCH RELEASE BEARINGS
CLUTCH RELEASE BEARING INSPECTION








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Condition Code Procedure
Collar broken ........... A ............ Require replacement.
Cracked ................. A ............ Require replacement.
Rough when rotated as an
assembly ............... B ............ Require replacement.
Seized .................. A ............ Require replacement.
Wear exceeds
specifications ......... B ............ Require replacement.
Worn close to the end of
its useful life ........ 1 ............ Suggest replacement.
Worn, affecting
performance ............ A ............ Require replacement.









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CLUTCH SLAVE CYLINDERS (CONCENTRIC)
CLUTCH SLAVE CYLINDER (CONCENTRIC) INSPECTION








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Condition Code Procedure
Bearing rough when rotated
as an assembly ......... B ............ Require replacement.
Bearing seized .......... A ............ Require replacement.
Bleeder pipe leaks ...... A .. Require repair or replacement.
Carrier assembly worn,
affecting performance .. A ........... Require replacement.
Collar broken ........... A ............ Require replacement.
Cracked ................. A ............ Require replacement.
Housing leaks ........... A ............ Require replacement.
Inoperative ............. A ............ Require replacement.
Release binding ......... A ............ Require replacement.
Spring broken ........... A ............ Require replacement.
Threads damaged ......... A .. Require repair or replacement.
Threads stripped (threads
missing) ............... A ............ Require replacement.
Worn, affecting
performance ............ A ............ Require replacement.









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CLUTCH SLAVE CYLINDERS (CONVENTIONAL OR EXTERNAL)
CLUTCH SLAVE CYLINDER (CONVENTIONAL OR EXTERNAL) INSPECTION








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Condition Code Procedure
Binding ................. A .. Require repair or replacement.
Bleeder port damaged (not
repairable) ............ A ........ ( 1) Require replacement.
Bleeder port damaged
(repairable) ........... A ............. ( 1) Require repair.
Bleeder screw broken off
in slave cylinder ...... A ........ ( 1) Require replacement.
Bleeder screw seized .... A ........ ( 2) Require replacement.
Bore corroded (pitted) .. B ............ Require replacement.
Bore grooved ............ A ............ Require replacement.
Threads damaged ......... A .. Require repair or replacement.
Threads stripped (threads
missing) ............... A ............ Require replacement.
( 1) - Only required if the hydraulic system must be opened.
( 2) - Seized is defined as a bleeder screw that cannot be
removed after a practical attempt at removing it has
been made.









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COMPANION FLANGES
See YOKES AND SLIP YOKES .
CONNECTORS
See WIRING HARNESSES AND CONNECTORS .
COOLER BYPASS VALVES
COOLER BYPASS VALVE INSPECTION








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Condition Code Procedure
Inoperative ............. A ............ Require replacement.
Installed incorrectly ... A ................. Require repair.
Leaking ................. A .. Require repair or replacement.
Restricted .............. A .. Require repair or replacement.









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COOLER LINES
COOLER LINE INSPECTION








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Condition Code Procedure
Abrasion damage, affecting
structural integrity ... A .. Require repair or replacement.
Abrasion damage, not
affecting structural
integrity .............. .. ........ No service suggested or
required.
Application incorrect ... B ............ Require replacement.
Attaching hardware
broken ................. A ... Require repair or replacement
of hardware.

performs its intended
function ............... A ............ Require replacement.
Weights missing ......... A ............ Require replacement.









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FLUID LEVEL INDICATORS
See DIP STICKS (FLUID LEVEL INDICATORS) .
FLUIDS AND LUBRICANTS
FLUID AND LUBRICANT INSPECTION








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Condition Code Procedure
Application incorrect ... B ........ ( 1) Require replacement.
At service interval ..... 3 ............ Suggest replacement.
Beyond service interval . 3 ............ Suggest replacement.
Burned .................. .. ......... ( 2) Further inspection
required.
Contaminated, for example,
fluid other than hydraulic
fluid present .......... A or B .... ( 3)( 4) Require service.
Exceeding service
interval ............... 3 ............ Suggest replacement.
Hydraulic fluid
incorrect .............. B ............ ( 5) Require service.
Level incorrect ......... B ..... Require correction of fluid
level.
Near service interval ... 3 ............ Suggest replacement.
Rubber master cylinder
cover gasket distorted
and gummy .............. A ............ ( 3) Require service.
Varnished ............... .. ......... ( 6) Further inspection
required.
( 1) - Determine and correct cause.
( 2) - Fluid that is burned indicates a serious problem.
Determine and correct the cause.
( 3) - If a fluid other than hydraulic fluid is present in the
hydraulic system which DOES affect the rubber parts, the
required service is to: 1) remove all components having
rubber parts from the system, 2) flush lines with
denatured alcohol or hydraulic cleaner, 3) repair or
replace all components having rubber parts, and 4) bleed
and flush with correct hydraulic fluid. (Code A)
( 4) - If a fluid other than hydraulic fluid is present in the
hydraulic system which DOES NOT affect the rubber parts,
the required service is to flush and fill with the
correct hydraulic fluid. (Code B)
( 5) - If a fluid other than specification hydraulic fluid is
present in the hydraulic system, the required service
is to flush and fill with the correct hydraulic fluid.
( 6) - Fluid that is varnished may indicate a serious problem.
Determine and correct the cause.









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FLYWHEELS
NOTE: Clutch disc replacement does not necessitate flywheel
reconditioning, unless other conditions justify the
reason to do so.

EG R F U NCTIO N T E STIN G

1988 J e ep C hero ke e
1983-88 Exhaust Emission Systems
JEEP EXHAUST GAS RECIRCULATION
TESTING
EGR VALVE
Valve Opening Test
1) With engine at normal operating temperature and at idle,
rapidly open and close throttle. Open throttle sufficiently to obtain
at least 1500 RPM. Movement should be noticed in EGR diaphragm.
2) If diaphragm does not move, probable causes are: faulty
vacuum signal to EGR, defective EGR diaphragm or defective
backpressure sensor diaphragm (if equipped), or leaks in vacuum lines
or connections.
Valve Closing Test
1) With engine at normal operating temperature and at idle,
manually depress EGR valve diaphragm. RPM should immediately drop,
indicating that EGR valve is not leaking and had been properly
cutting off exhaust gas flow at idle.
2) If there is no change in RPM and engine is idling
properly, exhaust gases are not reaching combustion chamber. Check
for plugged passage between EGR valve and intake manifold.
3) If engine idles poorly and RPM is not greatly affected by
manually moving diaphragm up, EGR valve is not closing off exhaust
gas flow. Check for carbon between pintle, leaking EGR valve gasket
or bad EGR valve.
COOLANT TEMPERATURE OVERRIDE (CTO) SWITCH
NOTE: Engine coolant temperature must be below 100F (38C) to
perform this test.
1) Check vacuum lines for leaks and correct routing.
Disconnect vacuum line at backpressure sensor (if equipped) or at EGR
valve, and attach this line to vacuum gauge.
2) Operate engine at 1500 RPM. No vacuum should be indicated
on gauge. If vacuum is shown, replace CTO switch.
3) Idle engine until coolant temperature exceeds 100
F
(38C) on 4-cylinder engines, or 115F (46C) on 6-cylinder and V8
engines.
4) Raise engine speed to 1500 RPM. Ported vacuum should be
shown on gauge. If not, replace CTO switch.
DUMP VALVE
1) With engine at normal operating temperature, remove dump
valve vacuum hose from manifold and plug manifold connection.
2) Raise engine speed to 2000 RPM. Vacuum should be present
at exhaust ports on bottom of valve. If not, replace valve.
3) Reconnect vacuum hose to manifold and raise engine speed
to 2000 RPM. No vacuum should be felt at exhaust ports on bottom of
valve. If vacuum is present, replace valve.
THERMAL VACUUM SWITCH (TVS)
1) With the air cleaner temperature below 40F (-4C),
disconnect vacuum hoses from TVS and connect vacuum source to large

EG R S YSTE M

1988 J e ep C hero ke e
1983-88 Exhaust Emission Systems
JEEP EXHAUST GAS RECIRCULATION
DESCRIPTION
Purpose of the Exhaust Gas Recirculation (EGR) system is to
limit formation of oxides of nitrogen (NOx) emissions. This is done by\
reducing high peak combustion temperatures at which NOx is formed. By
reintroducing some exhaust gas back into combustion chamber, high
temperatures are avoided. Thus NOx emissions formation is reduced.
System consists of vacuum-operated EGR valve and coolant
temperature override (CTO) switch. In addition, some models are
equipped with air cleaner-mounted thermal vacuum switch (TVS), and
some are equipped with an EGR vacuum dump valve.
OPERATION
When the EGR valve receives vacuum signal, through the CTO
switch, EGR valve opens and meters gases from exhaust manifold into
intake manifold. Individual component operation is as follows:
EGR VALVE
EGR valve is mounted on intake manifold. Exhaust gas is drawn
from exhaust crossover passage or exhaust manifold. Two types of EGR
valves are used: valve without backpressure sensor and valve with
integral backpressure sensor.
EGR Valve W/O Integral Backpressure Sensor
EGR valves are calibrated by use of different shapes of valve
pintles or orifices. Valve is normally held closed by spring (above
diaphragm). Valve opens by overcoming spring tension when vacuum is
sensed through coolant temperature override switch (CTO) and
backpressure sensor (if equipped).
EGR Valve W/Integral Backpressure Sensor
Calibration is accomplished by use of different diaphragm
spring loads and flow control orifices. This integral type unit
combines EGR valve and backpressure sensor functions into one
component. Restrictor plate is required with some engines.
Exhaust gas exerts backpressure inside exhaust manifold
whenever engine is running. This pressure is conducted through hollow
pintle stem into EGR diaphragm control chamber. If this pressure is
great enough to overcome spring tension against diaphragm, diaphragm
is moved against bleed valve and exhaust gas flow begins.
COOLANT TEMPERATURE OVERRIDE (CTO) SWITCH
Coolant temperature override (CTO) switch is located in
coolant passage at cylinder head or coolant passage at intake
manifold.
Inner port of switch is connected to EGR port on intake
manifold and outer port is connected to EGR valve, or EGR-TVS. Switch
opens at a preset temperature. Below these temperatures, no EGR is
possible.

Fig. 1: Jeep V8 Carbureted Engine EGR System
Courtesy of Chrysler Motors.
THERMAL VACUUM SWITCH (TVS)
Used only on carbureted 6-cylinder and V8 engines, this
switch is located in air cleaner and acts as on-off switch for EGR
system. It is controlled by ambient temperature in air cleaner. Switch
controls vacuum passage between CTO switch and EGR valve. Below preset
temperature, TVS blocks passage of vacuum delaying EGR operation and
improving cold driveability.