JEEP CHEROKEE 1988 Service Repair Manual

performance ............ A .. Require repair or replacement.
Fins damaged, not
affecting performance .. .. ........ No service suggested or
required.
Internal restrictions ... B .. Require repair or replacement.
Leaking ................. A .. Require repair or replacement.
Threads damaged ......... A .. Require repair or replacement.
Threads stripped (threads
missing) ............... A .. Require repair or replacement.
Tubes damaged, affecting
performance ............ A .. Require repair or replacement.
Tubes damaged, not
affecting performance .. .. ........ No service suggested or
required.









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TRANSMISSION MOUNTS
See MOUNTS (ENGINE, TRANSAXLE AND TRANSMISSION) .
TRANSMISSION PANS
TRANSMISSION PAN INSPECTION








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Condition Code Procedure
Bent, interfering with
filter or other internal
components ............. A .. Require repair or replacement.
Leaking ................. A .. Require repair or replacement.









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TRANSMISSION RANGE INDICATORS (PRNDL)
TRANSMISSION RANGE INDICATOR (PRNDL) INSPECTION








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Condition Code Procedure
Binding ................. A .. Require repair or replacement.
Broken .................. A .. Require repair or replacement.
Components missing ...... C .. Require replacement of missing
components.
Loose, affecting
performance ............ A .. Require repair or replacement.
Out of adjustment ....... A ................. Require repair.
Worn, affecting
performance ............ A .. Require repair or replacement.









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TUBES
See HOSES, LINES AND TUBES .
UNIVERSAL JOINTS (CARDON OR CROSS TYPE)
UNIVERSAL JOINT (CARDON OR CROSS TYPE) INSPECTION








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Condition Code Procedure
Attaching hardware
broken ................. A ... Require repair or replacement
of hardware.

Attaching hardware
missing ................ C .......... Require replacement of
hardware.
Attaching hardware not
functioning ............ A ... Require repair or replacement
of hardware.
Bearing cap distorted ... B ............ Require replacement.
Binding ................. A ............ Require replacement.
Cross (trunion) worn,
affecting performance .. A ............ Require replacement.
Double cardon centering
ball damaged ........... A ............ Require replacement.
Double cardon centering
ball worn, affecting
performance ............ A ............ Require replacement.
Double cardon centering
spring broken .......... A ............ Require replacement.
Double cardon centering
spring missing ......... C ............ Require replacement.
Double cardon centering
spring weak ............ A ............ Require replacement.
End cap seal cracked .... 2 ............ Suggest replacement.
End cap seal missing .... C .... Require replacement of seal.
Grease fitting broken ... A ...... (1) Require replacement of
grease fitting.
Grease fitting missing .. C ...... ( 2) Require replacement of
grease fitting.
Rust-colored powder around
end cap seals .......... A ............ Require replacement.
Threads damaged ......... A .. Require repair or replacement.
Threads stripped (threads
missing) ............... A ............ Require replacement.
Worn, affecting
performance ............ A ............ Require replacement.
( 1) - A broken grease fitting does not require replacement
of the U-Joint.
( 2) - A missing grease fitting does not require replacement
of the U-Joint.









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VACUUM CONTROLS
See ACTUATORS (VACUUM) .
VACUUM HOSES
See HOSES, LINES AND TUBES .
VACUUM MOTORS
See ACTUATORS (VACUUM) .
VACUUM-OPERATED SWITCHES
See SWITCHES.
VEHICLE SPEED SENSORS
See SPEED SENSORS (ELECTRONIC WHEEL AND VEHICLE) .
VENTS

VENT INSPECTION








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Condition Code Procedure
Broken .................. A ............ Require replacement.
Missing ................. C ............ Require replacement.
Plugged ................. A ........... (1) Require repair or
replacement.
( 1) - A plugged vent may force fluid past the seal.









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VIBRATION DAMPERS
VIBRATION DAMPER INSPECTION








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Condition Code Procedure
Broken .................. A ............ Require replacement.
Missing ................. C ............ Require replacement.
Out of position ......... B .. Require repair or replacement.
Threads damaged ......... A .. Require repair or replacement.
Threads stripped (threads
missing) ............... A ............ Require replacement.









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WHEEL ATTACHMENT HARDWARE
NOTE: For conditions noted below, also check conditions of
wheel stud holes.
CAUTION: Proper lug nut torque is essential. Follow recommended
torque specifications and tightening sequence. DO NOT
lubricate threads unless specified by the vehicle
manufacturer.
WHEEL ATTACHMENT HARDWARE INSPECTION









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Condition Code Procedure
Bent .................... A ............ Require replacement.
Broken .................. A ........ ( 1) Require replacement.
Loose ................... B ... Require repair or replacement
of affected component.
Lug nut installed
backward ............... B .. Require repair or replacement.
Lug nut mating surface
dished ................. A ..... Require replacement of nut.
Lug nut mating type
incorrect .............. B ..... Require replacement of nut.
Lug nut rounded ......... A . ( 2) Require replacement of nut.
Lug nut seized .......... A . ( 2) Require replacement of nut.
Stud incorrect .......... B .... Require replacement of stud.
Threads damaged ......... A .. Require repair or replacement.
Threads stripped (threads
missing) ............... A ............ Require replacement.
( 1) - Some manufacturers require replacement of all studs on
that wheel if two or more studs or nuts on the same wheel
are broken or missing.
( 2) - Only required if removing wheel.









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WHEEL SPEED SENSORS
See SPEED SENSORS (ELECTRONIC WHEEL AND VEHICLE) .
WIRING HARNESSES AND CONNECTORS
WIRING HARNESS AND CONNECTOR INSPECTION








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Condition Code Procedure
Application incorrect ... B .. Require repair or replacement.
Attaching hardware
broken ................. A ... Require repair or replacement
of hardware.
Attaching hardware
missing ................ C .......... Require replacement of
hardware.
Attaching hardware not
functioning ............ A .. Require repair or replacement
of hardware.
Connector broken ........ A .. Require repair or replacement.
Connector (Weatherpack
type) leaking .......... A .. Require repair or replacement.
Connector melted ........ A ........... ( 1) Require repair or
replacement.
Connector missing ....... C ............ Require replacement.
Insulation damaged,
conductors exposed ..... A .. Require repair or replacement.
Insulation damaged,
conductors not exposed . 1 ............ Suggest replacement.
Open .................... A .. Require repair or replacement.
Protective shield
(conduit) melted ....... 2 ........... ( 1) Suggest repair or
replacement.
Protective shield
(conduit) missing ...... 2 .. Suggest repair or replacement.
Resistance (voltage drop)
out of specification ... A .. Require repair or replacement.
Routed incorrectly ...... B ................. Require repair.
Secured incorrectly ..... B ................. Require repair.
Shorted ................. A .. Require repair or replacement.
Terminal broken ......... A .. Require repair or replacement.
Terminal burned, affecting
performance ............ A ........... ( 1) Require repair or
replacement.
Terminal burned, not
affecting performance .. 2 .. Suggest repair or replacement.
Terminal corroded,
affecting performance .. A .. Require repair or replacement.
Terminal corroded, not
affecting performance .. 2 .. Suggest repair or replacement.
Terminal loose, affecting
performance ............ B .. Require repair or replacement.
Terminal loose, not
affecting performance .. 1 .. Suggest repair or replacement.
Transmission connector
leaking ................ .. ..... See TRANSMISSION ASSEMBLY.
Voltage drop out of
specification .......... A .. Require repair or replacement.
( 1) - Determine cause and correct prior to repair or
replacement of part.

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YOKES AND SLIP YOKES
YOKE AND SLIP YOKE INSPECTION








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Condition Code Procedure
Bearing cap bore
distorted .............. A .. Require repair or replacement.
Bent .................... A ............ Require replacement.
Bolt holes elongated .... A .. Require repair or replacement.
Bushing or seal surface
worn, affecting
performance ............ A .. Require repair or replacement.
Leaking through soft yoke
plug ................... A ... Require repair or replacement
of soft yoke plug.
Retainer strap bent ..... A .......... Require replacement of
retainer strap.
Slip yoke broken ........ A ............ Require replacement.
Splines worn, affecting
performance ............ A ............ Require replacement.
Splines worn close
to the end of their
useful life ............ 1 ............ Suggest replacement.
Threads damaged ......... A .. Require repair or replacement.
Threads stripped (threads
missing) ............... A ............ Require replacement.
U-bolt damaged, affecting
performance ............ A ............. Require replacement
of U-bolts.
Yoke damaged, affecting
performance ............ A .. Require repair or replacement.









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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

outlet.
2) Apply vacuum to TVS. TVS should hold vacuum. If not,
replace TVS.
3) Start engine and warm air cleaner to 55
F (13C), or
greater. TVS should not hold vacuum. If it does, replace TVS.

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.

Fig. 2: Jeep 6-Cylinder Carbureted Engine EGR System
Courtesy of Chrysler Motors.
EGR DUMP VALVE
Used on some models, EGR dump valve is connected in series
with vacuum source and EGR valve. Valve is used to eliminate EGR
function at low vacuum levels. When vacuum drops below predetermined
level, valve "dumps" vacuum rather than allowing it to flow to EGR