1988 JEEP CHEROKEE oil reset

lubricant to axle flange bearing bore and install axle.
YOKE & PINION OIL SEAL
Removal
1) Raise and support vehicle. Remove wheels and brake drums.
Mark and remove drive shaft. Using an INCH lb. torque wrench, record
torque required to rotate pinion several revolutions.
2) Hold yoke from turning and remove pinion nut. Mark drive
pinion shaft and yoke for reassembly reference. Remove yoke and pinion
oil seal.
Installation
1) Coat new seal with rear axle lubricant and install. Align
marks made at disassembly and install yoke. Install new pinion nut and
tighten just enough to remove end play.
CAUTION: DO NOT overtighten pinion nut. If desired preload is
exceeded, a new collapsible pinion spacer sleeve must be
installed and drive pinion preload reset.
2) Using an INCH lb. torque wrench, check torque required to
turn pinion. Refer to torque reading recorded during disassembly and
add 5 INCH lbs. (.6 N.m) for correct preload. Tighten pinion nut
slightly and recheck preload. Repeat procedure until desired preload
is obtained.
REAR AXLE ASSEMBLY
Removal
1) Raise and support vehicle. Remove wheels and brake drums.
Disconnect brake hose-to-axle connection and plug line.
2) Disconnect parking brake cable at brake equalizer. Mark
and remove drive shaft. Disconnect track bar at axle bracket (if
equipped). Remove axle vent tube at axle. Support axle assembly.
Remove spring "U" bolts and tie plates.
3) Loosen, but do not remove, bolts which attach front of
rear spring to frame brackets. Lift axle to relieve axle weight from
springs and remove bolts retaining springs to shackles. Lower springs
to floor. Lower jack and remove axle assembly.
NOTE: Factory axles are shipped without lubricant. When adding
lubricant, position axle horizontally with yoke end of
pinion housing facing downward. Turn pinion shaft several
times to lubricate bearings.
Installation
1) To install, support axle assembly with jack and slide axle
into place. Raise, align and install spring-to-frame and shackle
bolts. Tighten spring-to-frame and shackle bolts to 111 ft. lbs. (150
N.m). Install brake hose, axle vent tube and parking brake cable.
Align and connect drive shaft.
2) Bleed hydraulic system and adjust parking brake cable.
Ensure axle is filled with 75-90W gear lubricant. Ensure spring
centering bolt heads are seated in axle spring seat before tightening
"U" bolts.
OVERHAUL
DISASSEMBLY
NOTE: It is not necessary to remove axle assembly from vehicle to

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

Incorrect ignition timing Reset ignition timing,
See TUNE-UP
Leaking valves Replace valves, See
ENGINES
Worn fuel pump diaphragm Replace diaphragm or
or piston piston









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Intake Backfire Improper ignition timing Reset ignition timing,
See TUNE-UP
Faulty accelerator pump Replace accelerator
discharge pump
Improper choke operation Check choke and adjust
as required
Defective EGR valve Replace EGR valve
Fuel mixture too lean Reset air/fuel mixture,
See TUNE-UP
Choke valve initial Reset choke valve
clearance too large initial clearance









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Exhaust Backfire Vacuum leak Inspect and repair
vacuum system
Faulty vacuum diverter Replace vacuum diverter
valve valve
Faulty choke operation Check choke and adjust
as required
Exhaust system leak repair exhaust system
leak









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Engine Ignition timing too far Reset ignition timing,
Detonation advanced See TUNE-UP
Faulty ignition system Check ignition timing,
See TUNE-UP
Spark plugs loose or Retighten or replace
faulty plugs
Fuel delivery system Inspect lines, pump and
clogged filter for clog
EGR valve inoperative Replace EGR valve
PCV system inoperative Inspect and/or replace
hoses or valve
Vacuum leaks Check vacuum system and
repair leaks
Excessive combustion
chamber deposits Remove built-up
deposits
Leaking, sticking or Inspect and/or replace
broken valves valves









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External Oil Fuel pump improperly seated Remove pump, replace
Leakage or worn gasket gasket and seat
properly
Oil pan gasket broken or Straighten pan and
pan bent replace gasket
Timing chain cover gasket Replace timing chain
broken cover gasket
Rear main oil seal worn Replace rear main oil
seal
Oil pan drain plug not Remove and reinstall
seated properly drain plug
Camshaft bearing drain Remove restriction
hole blocked
Oil pressure sending Remove and reinstall
switch leaking sending switch









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batteries
Bad starter connections Check connections
or bad starter and/or replace
batteries









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Engine Cranks Bad battery connections Check connections
Slowly, Won't or dead batteries and/or replace
Start batteries
Engine oil too heavy Replace engine oil









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Engine Cranks Glow plugs not functioning Check glow plug system,
Normally, But see FUEL SYSTEMS
Will Not Start Glow plug control not Check controller, see
functioning FUEL SYSTEMS
Fuel not injected into Check fuel injectors,
cylinders see FUEL SYSTEMS
No fuel to injection pump Check fuel delivery
system
Fuel filter blocked Replace fuel filter
Fuel tank filter blocked Replace fuel tank
filter
Fuel pump not operating Check pump operation
and/or replace pump
Fuel return system blocked Inspect system and
remove restriction
No voltage to fuel solenoid Check solenoid and
connections
Incorrect or contaminated Replace fuel
fuel
Incorrect injection pump Re-adjust pump timing,
timing see FUEL SYSTEMS
Low compression Check valves, pistons,
rings, see ENGINES
Injection pump malfunction Inspect and/or replace
injection pump









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Engine Starts, Incorrect slow idle Reset idle adjustment,
Won't Idle adjustment see TUNE-UP
Fast idle solenoid Check solenoid and
malfunctioning connections
Fuel return system blocked Check system and remove
restrictions
Glow plugs go off too soon See glow plug diagnosis
in FUEL SYSTEMS
Injection pump timing Reset pump timing, see
incorrect FUEL SYSTEMS
No fuel to injection pump Check fuel delivery
system
Incorrect or contaminated Replace fuel
fuel
Low compression Check valves, piston,
rings, see ENGINES
Injection pump malfunction Replace injection pump,
see FUEL SYSTEMS
Fuel solenoid closes in RUN Check solenoid and
position connections









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Engines Starts/ Incorrect slow idle Reset slow idle, see
Idles Rough W/out adjustment TUNE-UP
Smoke or Noise Injection line fuel leaks Check lines and
connections
Fuel return system blocked Check lines and
connections

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High Pitched Whine Distance too great Align starter or check
During Cranking between starter that correct starter
Before Engine pinion and flywheel and flywheel are being
Fires but Engine used
Fires and Cranks
Normally









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High Pitched Distance too small between
Whine After Engine starter pinion and flywheel
Fires With Key Flywheel runout contributes
released. Engine to the intermittent nature
Fires and Cranks
Normally









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TUNE-UP TROUBLE SHOOTING - GAS ENGINE VEHICLES
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 SPARK PLUG TROUBLE SHOOTING CHARTS









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CONDITION POSSIBLE CAUSE CORRECTION








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Normal Spark Light Tan or Gray deposits No Action
Plug Condition
Electrode not burned or No Action
fouled
Gap tolerance not changed No Action









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Cold Fouling or Overrich air/fuel mixture Adjust air/fuel
Carbon Deposits mixture, see ENGINE
PERFORMANCE section
Faulty choke Replace choke
assembly, see ENGINE
PERFORMANCE section
Clogged air filter Clean and/or replace
air filter
Incorrect idle speed or Reset idle speed and/
dirty carburetor or clean carburetor
Faulty ignition wires Replace ignition
wiring
Prolonged operation Shut engine off
at idle during long idle
Sticking valves or worn Check valve train
valve guide seals









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Wet Fouling Worn rings and pistons Install new rings and
or Oil Deposits pistons

ignition switch
Open circuit between Repair circuit
ignition switch and
starter solenoid









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Engine Runs Fuel lines leaking or Tighten fitting,
Rough clogged remove restriction
Initial timing incorrect Reset ignition timing
see ENGINE PERFORMANCE
Centrifugal advance Repair distributor
malfunction advance
Defective spark plugs or Replace plugs or plug
wiring wiring









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Component Failure Spark arc-over on cap, Replace cap, rotor or
rotor or coil or coil
Defective pick-up coil Replace pick-up coil
Defective ignition coil Replace ignition coil
Defective vacuum unit Replace vacuum unit
Defective control module Replace control module









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BASIC ELECTRONIC IGNITION TROUBLE SHOOTING
CHARTS - USING OSCILLOSCOPE PATTERNS









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CONDITION POSSIBLE CAUSE CORRECTION








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Firing Voltage Retarded ignition timing Reset ignition
Lines are the Same, timing, see ENGINE
but Abnormally High PERFORMANCE section
Fuel mixture too lean Readjust carburetor,
see ENGINE PERFORMANCE
High resistance in coil Replace coil wire
wire
Corrosion in coil tower Clean and/or replace
terminal coil
Corrosion in distributor Clean and/or replace
coil terminal distributor cap









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Firing Voltage Fuel mixture too rich Readjust carburetor,
Lines are the Same see ENGINE PERFORMANCE
but Abnormally Low
Breaks in coil wire causing Replace coil wire
arcing
Cracked coil tower causing Replace coil
arcing
Low coil output Replace coil
Low engine compression Determine cause and

Worn or dirty needle valve Clean carburetor, see
and seat ENGINE PERFORMANCE
Float sticking Readjust or replace
float see the ENGINE
PERFORMANCE section
Incorrect choke adjustment Reset choke adjustment
see ENGINE PERFORMANCE
Defective coil Replace coil
Improper spark plug gap Regap spark plugs
Incorrect ignition timing Reset ignition timing
see ENGINE PERFORMANCE









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Detonation Over-advanced ignition Reset ignition timing
timing see ENGINE PERFORMANCE
Defective spark plugs Replace spark plugs
Fuel lines clogged Clean fuel lines
EGR system malfunction Check and repair EGR
system
PCV system malfunction Repair PCV system
Vacuum leaks Check and repair
vacuum system
Loose fan belts Tighten or replace
fan belts, see ENGINE
PERFORMANCE
Restricted airflow Remove restriction
Vacuum advance malfunction Check distributor
operation









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Dieseling Binding carburetor linkage Eliminate binding
Binding throttle linkage Eliminate blinding
Binding choke linkage or Eliminate binding
fast idle cam
Defective idle solenoid Replace idle solenoid
see ENGINE PERFORMANCE
Improper base idle speed Reset idle speed, see
see ENGINE PERFORMANCE
Incorrect ignition timing Reset ignition timing
see ENGINE PERFORMANCE
Incorrect idle mixture Reset idle mixture,
setting see ENGINE PERFORMANCE









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Faulty Incorrect ignition timing Reset ignition timing
Acceleration see ENGINE PERFORMANCE

Engine cold and choke too Adjust choke and
lean allow engine to warm-
up
Defective spark plugs Replace spark plugs
Defective coil Replace coil









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Faulty Low Speed Clogged idle transfer slots Clean idle transfer
Operation slots, see FUEL
Restricted idle air bleeds Disassemble and clean
and passages carburetor, see FUEL
Clogged air cleaner Replace air filter
Defective spark plugs Replace spark plugs
Defective ignition wires Replace ignition wire
see ENGINE PERFORMANCE
Defective distributor cap Replace distributor
cap









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Faulty High Speed Incorrect ignition timing Reset ignition timing
Operation see ENGINE PERFORMANCE
Defective distributor Replace advance
centrifugal advance mechanism
Defective distributor Replace advance unit
vacuum advance
Incorrect spark plugs or Check gap and/or
plug gap replace spark plugs
Faulty choke operation Check choke and
repair as required
Clogged vacuum passages Remove restrictions
Improper size or clogged Check jet size and
main jet clean, see FUEL
Restricted air cleaner Check filter and
replace as necessary
Defective distributor cap, Replace cap, rotor or
rotor or coil coil









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Misfire at All Defective spark plugs Replace spark plugs
Speeds
Defective spark plug wires Replace spark plug
wires
Defective distributor cap, Replace cap, rotor,
rotor, or coil or coil
Cracked or broken vacuum Replace vacuum hoses
hoses