1988 JEEP CHEROKEE parking brake
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sluggish See DISC BRAKES or
BRAKE SYSTEM
Master cylinder piston
stuck See MASTER CYLINDERS
or BRAKE SYSTEM
Brake fade due to incorrect
pads for linings Replace pads or linings
Linings or pads glazed Replace pads or linings
Worn drums Reface or replace drums
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Excessive Pedal
Travel Partial brake system failure Check fluid and pipes
Insufficient fluid in
master cylinder See MASTER CYLINDERS or
BRAKE SYSTEM
Air trapped in system See BRAKE BLEEDING or
BRAKE SYSTEM
Rear brakes not adjusted See Adjustments in DRUM
BRAKES or BRAKE SYSTEM
Bent shoe or lining See DRUM BRAKES or
BRAKE SYSTEM
Plugged master cylinder cap See MASTER CYLINDERS
or BRAKE SYSTEM
Improper brake fluid Replace brake fluid
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Pedal Travel
Decreasing Compensating port plugged See MASTER CYLINDERS
or BRAKE SYSTEM
Swollen cup in master
cylinder See MASTER CYLINDERS
or BRAKE SYSTEM
Master cylinder piston
not returning See MASTER CYLINDERS
or BRAKE SYSTEM
Weak shoe retracting springs See DRUM BRAKES
BRAKE SYSTEM
Wheel cylinder piston
sticking See DRUM BRAKES or
BRAKE SYSTEM
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Dragging
Brakes Master cylinder pistons
not returning See MASTER CYLINDERS
BRAKE SYSTEM
Restricted brake lines
or hoses Check line routing
Incorrect parking brake
adjustment See DRUM BRAKES
BRAKE SYSTEM
Page 1234 of 1378
Parking Brake cables frozen See DRUM BRAKES
BRAKE SYSTEM
Incorrect installation of
inboard disc pad Remove and replace
correctly
Power booster output
rod too long See POWER BRAKE UNITS
BRAKE SYSTEM
Brake pedal not returning See DISC, DRUM BRAKES
freely BRAKE SYSTEM
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Brakes Grab or
Uneven Braking
Action Malfunction of combination See CONTROL VALVE or
valve BRAKE SYSTEM
Malfunction of power brake See POWER BRAKE UNITS
unit or BRAKE SYSTEM
Binding brake pedal See DISC, DRUM BRAKES
or BRAKE SYSTEM
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Pulsation or
Roughness Uneven pad wear caused by See DISC BRAKES or
caliper BRAKE SYSTEM
Uneven rotor wear See DISC BRAKES or
BRAKE SYSTEM
Drums out-of-round Reface or replace drums
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ENGINE MECHANICAL
COOLING SYSTEM 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.
COOLING SYSTEM TROUBLE SHOOTING
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CONDITION POSSIBLE CAUSE CORRECTION \
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Overheating Coolant Leak Fill/Pressure Test
System
A/C Condenser Fins Clogged Remove/Clean Condenser
Radiator Fins Clogged Remove/Clean Radiator
Thermostat Stuck Closed Replace Thermostat
Clogged Cooling System
Passages Clean/Flush Cooling
System
Page 1297 of 1378
Fig. 2: 4.0L & 4.2L Timing Marks & Firing Order
Magnetic probe located at 9.5 degrees ATDC on 4.2L.
IGNITION TIMING (4.0L)
Information not available from manufacturer.
IGNITION TIMING (4.2L)
NOTE: Engines are equipped with a receptacle for a magnetic probe
timing light, located 9.5 degrees ATDC. Do not use this
location to check timing with a conventional light, use a
magnetic probe timing light.
Standard Timing Procedure
1) Apply parking brake, and place transmission in Neutral
(Park for automatic transmissions). Operate engine to normal operating\
temperature. Turn ignition off. Install timing light.
2) Connect tachometer. Disconnect and plug vacuum hose at
distributor. Disconnect vacuum switch assembly wire connector, located
on top of valve cover. Start engine and increase engine speed to 1600
RPM.
3) Compare timing to specification. See
IGNITION TIMING SPECIFICATIONS table. To adjust timing, loosen
distributor clamp bolt and turn distributor. Recheck timing after
clamp bolt is tightened.
Alternate Timing Procedure
1) Apply parking brake and place transmission in Neutral
(Drive for automatic transmissions). Operate engine to obtain normal
operating temperature. Turn ignition off. Install timing light.
2) Disconnect and plug vacuum switch hose (Red and Black
Page 1298 of 1378
wires connected to switch). Disconnect distributor vacuum advance hose
and connect hose to vacuum switch. Disconnect wire connector from
knock sensor, located in cylinder head.
3) Using a jumper wire, ground knock sensor wire connector to
engine block. Start engine. With engine at idle speed (solenoid
energized), check timing. Adjust timing to one degree more than
specification (if required). See Emission Control Label.
IGNITION TIMING SPECIFICATIONS (DEGREES BTDC@RPM) - 4.2L
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Application Man. Trans. Auto. Trans.
50 State ............. 9 @ 1600 ............... 9 @ 1600
High Altitude ........ 16 @ 1600 ............. 16 @ 1600
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HOT (SLOW) IDLE RPM
4.0L
1) Apply parking brake and place transmission in Neutral
(Drive for automatic transmissions). Operate engine to normal
operating temperature. Turn ignition off.
2) Ensure all accessories are off. Connect positive
tachometer lead to terminal "D1-1" and negative lead to "D2-7" of
diagnostic connectors. See Fig. 3. Disconnect air stepper motor
connector and TPS wiring connector. See Fig. 4.
Fig. 3: Diagnostic Connector Terminal Identification
Courtesy of Chrysler Motors.
Page 1300 of 1378
Fig. 5: Adjusting Idle RPM
Courtesy of Chrysler Motors.
6) Adjust idle RPM screw to obtain idle speed of 750F50 RPM.
Once correct idle RPM is obtained, seal the welch plug cavity with RTV
sealant. Reconnect air stepper motor and TPS.
4.2L
1) Warm engine to normal operating temperature. Apply parking
brake. Place automatic transmission in Drive (Neutral on manual
transmission). Disconnect and plug vacuum hose from vacuum actuator.
Disconnect solenoid wire connector.
2) Adjust curb idle screw to obtain correct curb idle. See
CURB IDLE SPEED (RPM) table. Apply 10-15 in. Hg vacuum to vacuum
actuator. With throttle positioner fully extended, adjust screw on
throttle lever, to set vacuum actuator RPM to specification. See
VACUUM ACTUATOR & SOLENOID IDLE (RPM) table. Disconnect vacuum pump.
3) Apply battery voltage to solenoid with a jumper wire. Turn
A/C on (if equipped). Open throttle, allowing solenoid to fully
extend. Adjust solenoid adjusting screw to obtain solenoid idle RPM.