1988 JEEP CHEROKEE check engine
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![JEEP CHEROKEE 1988 Service Repair Manual Brakes dragging See BRAKES article \
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\](/manual-img/16/57037/w960_57037-1272.png "JEEP CHEROKEE 1988 Service Repair Manual Brakes dragging See BRAKES article \
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Brakes dragging See BRAKES article \
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Instability Low or uneven tire Inflate to proper
pressure pressure
Loose or worn wheel See FRONT SUSPENSION
bearings article
Loose or worn idler arm See FRONT SUSPENSION
bushing article
Loose or worn strut See FRONT SUSPENSION
bushings article
Incorrect front wheel See WHEEL ALIGNMENT
alignment article
Steering gear not See MANUAL STEERING
centered GEARS article
Springs or shock Check and replace if
necessary
Improper cross shaft See MANUAL STEERING
GEARS article
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POWER STEERING 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.
BASIC POWER STEERING TROUBLE SHOOTING CHART
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CONDITION POSSIBLE CAUSE CORRECTION \
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Rattle or Pressure hoses touching Adjust to proper
Chucking Noise engine parts clearance
Loose Pitman shaft Adjust or replace if
necessary
Tie rods ends or Pitman Tighten and check system
arm loose
Rack and pinion mounts Tighten all mounting
loose bolts
Free play in worm and See POWER STEERING GEAR
article
Loose sector shaft or See POWER STEERING GEAR
thrust bearing adjustment
Free play in pot coupling See STEERING COLUMN
article
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Reaction ring sticking See POWER STEERING GEAR
in housing head article
Steering pump internal See POWER STEERING PUMP
leakage article
Steering gear-to-column See STEERING COLUMN
misalignment article
Lack of lubrication in Service front suspension
linkage
Lack of lubrication in Service front suspension
ball joints
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Increased Effort High internal pump leakage See POWER STEERING PUMP
When Turning article
Wheel Fast Power steering pump belt Adjust or replace if
Foaming, Milky slipping necessary
Power Steering
Fluid, Low Fluid Low fluid level Check and fill to
Level or Low proper level
Pressure
Engine idle speed to low Adjust to correct
setting
Air in pump fluid system See POWER STEERING PUMP
article
Pump output low See POWER STEERING PUMP
article
Steering gear See POWER STEERING GEAR
malfunctioning article
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Wheel Surges Low fluid level Check and fill to proper
or Jerks level
Loose fan belt Adjust or replace if
necessary
Insufficient pump See POWER STEERING PUMP
pressure article
Sticky flow control valve See POWER STEERING PUMP
article
Linkage hitting oil pan Replace bent components
at full turn
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Kick Back or Air in pump fluid system See POWER STEERING PUMP
Free Play article
Worn poppet valve in See POWER STEERING PUMP
steering gear article
Excessive over center See POWER STEERING GEAR
lash article
Thrust bearing out of See POWER STEERING GEAR
adjustment article
Page 1277 of 1378
Free play in pot coupling See POWER STEERING PUMP
article
Steering gear coupling See POWER STEERING PUMP
loose on shaft article
Steering disc mounting Tighten or replace if
bolts loose necessary
Coupling loose on worm Tighten or replace if
shaft necessary
Improper sector shaft See POWER STEERING GEAR
adjustment article
Excessive worm piston See POWER STEERING GEAR
side play article
Damaged valve lever See POWER STEERING GEAR
article
Universal joint loose Tighten or replace if
necessary
Defective rotary valve See POWER STEERING GEAR
article
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No Power When Sticking flow control See POWER STEERING PUMP
Parking valve article
Insufficient pump See POWER STEERING PUMP
pressure output article
Excessive internal pump See POWER STEERING PUMP
leakage article
Excessive internal gear See POWER STEERING PUMP
leakage article
Flange rubs against gear See STEERING COLUMN
adjust plug article
Loose pump belt Adjust or replace if
necessary
Low fluid level Check and add proper
amount of fluid
Engine idle too low Adjust to correct
setting
Steering gear-to-column See STEERING COLUMN
misaligned article
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No Power, Left turn reaction seal See POWER STEERING GEAR
Left Turn "O" ring worn article
Left turn reaction seal See POWER STEERING GEAR
damaged/missing article
Cylinder head "O" ring See POWER STEERING PUMP
damaged article
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Page 1288 of 1378
Fig. 2: TBI Diagnostic Connector & Terminal ID
Courtesy of Chrysler Motors.
2) With plunger extended, disconnect ISC motor electrical
connector. Start engine. Engine idle speed should be 3300-3700 RPM. If
not, turn plunger hex head to obtain 3500 RPM. See Fig. 3.
3) To fully retract ISC motor, hold closed throttle switch
plunger inward while opening throttle. Closed throttle switch plunger
should not touch throttle lever when throttle is closed. If this
occurs, check linkage and/or cable for binding.
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TU NE-U P - 6 -C YL
1988 J e ep C hero ke e
1987-88 TUNE-UP
Jeep 6 Cylinder Tune-Up
Cherokee, Comanche, Wagoneer, Wrangler
IDENTIFICATION
ENGINE IDENTIFICATION
Engine can be identified by the fourth character of engine
Build Date Code number, located on a tag attached to right side of
block between No. 2 and 3 cylinders.
The same code letter is also the fourth character in the
Vehicle Identification Number (VIN), located at top left corner of
dashboard.
ENGINE CODE TABLE
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Engine Code
4.0L (242") MPFI ....................................... M
4.2L (258") 2-Bbl. ..................................... C
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TUNE-UP NOTES
NOTE: When performing tune-up procedures described in this
article, these notes and precautions must be followed.
Due to late changes and corrections, always refer to Emission
Control Label in engine compartment before attempting tune-up. If
manual and label specifications differ, use label specifications.
When performing tune-up on vehicles equipped with a catalytic
converter, do not allow or create an engine misfire in one or more
cylinders for an extended period of time. Damage to converter from
overheating may occur due to loading with unburned fuel.
TESTING
ENGINE COMPRESSION
Check compression pressure with engine at normal operating
temperature, all spark plugs removed, throttle and choke valves wide
open and engine at cranking speed.
COMPRESSION SPECIFICATIONS TABLE
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Application Specification
Compression Ratio .................................. 9.2:1
Compression Pressure ....... 120-150 psi (8.4-10.5 kg/cm
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Maximum Variation Between Cylinders .. 30 psi (2.1 kg/cm) \
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HIGH TENSION WIRE RESISTANCE
Do not puncture spark plug wires with any type of probe.
Remove spark plug wire and check resistance using an ohmmeter.
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inlet line or filter disconnected at carburetor. Disconnect fuel
return line at fuel filter and plug nipple on filter. Make all tests
at idle speed. See FUEL PUMP SPECIFICATIONS TABLE .
FUEL PUMP SPECIFICATIONS TABLE
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Application Pressure Volume
** psi (kg/cm) ( 1) Pts. (L)
4.0L .................... ( 2) 31 (2.1) ............ 1.0 (.47)
4.0L .................... ( 3) 39 (2.6) ............ 1.0 (.47)
4.2L .................. 4.0-5.0 (.28-.35) ......... 1.0 (.47)
( 1) - Volume per 30 seconds.
( 2) - With the vacuum hose connected to the pressure regulator.
( 3) - With the vacuum hose removed from the pressure regulator.
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ADJUSTMENTS
VALVE ARRANGEMENT
* E-I-I-E-I-E-E-I-E-I-I-E (Front-to-rear).
VALVE CLEARANCE
All engines are equipped with hydraulic lifters. Valve
clearance is not adjustable.
IGNITION COIL WIRE
Remove ignition coil wire from coil and distributor cap.
Check terminals for corrosion and clean (if necessary). Check coil
wire resistance. Replace wire if resistance is excessive.
HIGH TENSION WIRE RESISTANCE (OHMS) TABLE
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Wire Length Minimum Maximum
0-15" .................. 3000 ................... 10,000
15-25" ................. 4000 ................... 15,000
25-35" ................. 6000 ................... 20,000
Over 35" ............... 8000 ................... 25,000
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DISTRIBUTOR
4.0L
Information not available from manufacturer.
4.2L
All models are equipped with Motorcraft Solid State Ignition
(SSI) systems. No adjustments are required.
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
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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.