1988 JEEP CHEROKEE check engine

Water Pump Malfunction Replace Water Pump
Fan Clutch Malfunction Replace Fan Clutch
Retarded Ignition Timing Reset Ignition Timing
Cooling Fan Malfunction Test Cooling Fan/
Circuit
Cooling Fan Motor
Malfunction Test Fan Motor
Cooling Fan Relay
Malfunction Test Fan Relay
Faulty Radiator Cap Replace Radiator Cap
Broken/Slipping Fan Belt Replace Fan Belt
Restricted Exhaust Repair Exhaust System









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Corrosion Impurities In Coolant Clean/Flush System








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Coolant Leakage Damaged hose Replace Hose
Leaky Water Pump Replace Water Pump
Damaged Radiator Seam Replace/Repair Radiator
Leaky Thermostat Cover Replace Thermostat
Cover
Cylinder Head Problem Check Head/Head Gasket
Leaky Freeze Plugs Replace Freeze Plugs









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Recovery System Inoperative
Loose and/or Defective
Radiator Cap Replace Radiator Cap
Overflow Tube Clogged
and/or Leaking Repair Tube
Recovery Bottle Vent
Restricted Clean Vent









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No Heater Core Flow
Collapsed Heater Hose Replace Heater Hose
Plugged Heater Core Clean/Replace Heater
Core
Faulty Heater Valve Replace Heater Valve









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GASOLINE ENGINE - MECHANICAL 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 GASOLINE ENGINE - MECHANICAL TROUBLE SHOOTING CHART









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CONDITION POSSIBLE CAUSE CORRECTION








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Engine Lopes At Intake manifold-to-head Replace manifold
Idle leaks gasket, See ENGINES
Blown head gasket Replace head gasket,
See ENGINES
Worn timing gears, chain Replace gears, chain or
or sprocket sprocket
Worn camshaft lobes Replace camshaft, See
ENGINES
Overheated engine Check cooling system,
See COOLING
Blocked crankcase vent Remove restriction
valve
Leaking EGR valve Repair leak and/or
replace valve
Faulty fuel pump Replace fuel pump









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Engine Has Low Leaking fuel pump Repair leak and/or
Power replace fuel pump
Excessive piston-to-bore Install larger pistons,
clearance See ENGINES
Sticking valves or weak Check valve train
valve springs components, See ENGINES
Incorrect valve timing Reset valve timing, See
ENGINES
Worn camshaft lobes Replace camshaft, See
ENGINES
Blown head gasket Replace head gasket.
See ENGINES.
Clutch slipping Adjust pedal and/or
replace components, See
ENGINES
Engine overheating Check cooling system,
See COOLING
Auto. Trans. pressure
regulator valve faulty Replace pressure
regulator valve
Auto. Trans. fluid level Add fluid as necessary
too low
Improper vacuum diverter
valve operation Replace vacuum diverter
valve
Vacuum leaks Inspect vacuum system
and repair as required
Leaking piston rings Replace piston rings,
See ENGINES









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Faulty High Low fuel pump volume Replace fuel pump
Speed Operation
Leaking valves or worn Replace valves and/or
springs, See ENGINES
Incorrect valve timing Reset valve timing,See
ENGINES
Intake manifold restricted Remove restriction
Worn distributor shaft Replace distributor









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Faulty Improper fuel pump stroke Remove pump and reset
Acceleration pump stroke

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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ENGINES








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High Oil Improper grade of oil Replace with proper oil
Pressure Oil pressure relief valve Eliminate binding
stuck closed
Oil pressure sender or Replace sender or gauge
gauge faulty









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Noisy Main Inadequate oil supply Check oil delivery to
Bearings main bearings
Excessive main bearing Replace main bearings,
clearance See ENGINES
Excessive crankshaft end Replace crankshaft, See
play ENGINES
Loose flywheel or torque Tighten attaching bolts
converter
Loose or damaged vibration Tighten or replace
damper vibration damper
Crankshaft journals Re-grind crankshaft
out-of-round journals
Excessive belt tension Loosen belt tension









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Noisy Connecting Excessive bearing clearance Replace bearing, See
Rods or missing bearing ENGINES
Crankshaft rod journal Re-grind crankshaft
out-of-round journal
Misaligned connecting rod Remove rod or cap and
or cap realign
Incorrectly tightened rod Remove and re-tighten
bolts rod bolts









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Noisy Pistons Excessive piston-to-bore Install larger pistons,
and Rings clearance See ENGINES
Bore tapered or out-of-round Rebore block
Piston ring broken Replace piston rings,
See ENGINES
Piston pin loose or seized Replace piston pin, See
ENGINES
Connecting rods misaligned Realign connecting rods
Ring side clearance too Replace with larger or
loose or tight smaller rings
Carbon build-up on piston Remove carbon









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Noisy Valve Worn or bent push rods Replace push rods, See
Train ENGINES
Worn rocker arms or bridged Replace push rods, See
pivots ENGINES
Dirt or chips in valve Remove lifters and
lifters remove dirt/chips
Excessive valve lifter Replace valve lifters,
leak-down See ENGINES
Valve lifter face worn Replace valve lifters,
See ENGINES
Broken or cocked valve replace or reposition
springs springs
Too much valve stem-to-guide Replace valve guides,
clearance See ENGINES
Valve bent Replace valve, See
ENGINES
Loose rocker arms Retighten rocker arms,
See ENGINES
Excessive valve seat Reface valve seats, See
run-out ENGINES

Missing valve lock Install new valve lock
Excessively worn camshaft Replace camshaft, See
lobes ENGINES
Plugged valve lifter oil Eliminate restriction
holes or replace lifter
Faulty valve lifter check Replace lifter check
ball ball, See ENGINES
Rocker arm nut installed Remove and reinstall
upside down correctly
Valve lifter incorrect for Remove and replace
engine valve lifters
Faulty push rod seat or Replace plunger or push
lifter plunger rod









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Noisy Valves Improper valve lash Re-adjust valve lash,
See ENGINES
Worn or dirty valve lifters Clean and/or replace
lifters
Worn valve guides Replace valve guides,
See ENGINES
Excessive valve seat or Reface seats or valve
face run-out face
Worn camshaft lobes Replace camshaft, See
ENGINES
Loose rocker arm studs Re-tighten rocker arm
studs, See ENGINES
Bent push rods Replace push rods, See
ENGINES
Broken valve springs Replace valve springs,
See ENGINES









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Burned,Sticking Weak valve springs or Replace valves and/or
or Broken Valves warped valves springs, See ENGINES
Improper lifter clearance Re-adjust clearance or
replace lifters
Worn guides or improper Replace valve guides,
guide clearance See ENGINES
Out-of-round valve seats Re-grind valve seats
or improper seat width
Gum deposits on valve Remove deposits
stems, seats or guides
Improper spark timing Re-adjust spark timing









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Broken Undersize pistons Replace with larger
Pistons/Rings pistons, See ENGINES
Wrong piston rings Replace with correct
rings, See ENGINES
Out-of-round cylinder bore Re-bore cylinder bore
Improper connecting rod Remove and realign
alignment connecting rods
Excessively worn ring Replace pistons, See
grooves ENGINES
Improperly assembled Re-assemble pin-to
piston pins -piston, See ENGINES
Insufficient ring gap Install new rings, See
clearance ENGINES
Engine overheating Check cooling system
Incorrect ignition timing Re-adjust ignition
timing, See TUNE-UP









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Excessive Leaks at manifold to Replace manifold or
Exhaust Noise head, or to pipe pipe gasket
Exhaust manifold Replace exhaust

cracked or broken manifold, See ENGINES








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ENGINE PERFORMANCE
CARBURETOR 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 COLD START SYMPTOMS TROUBLE SHOOTING CHART









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CONDITION POSSIBLE CAUSE CORRECTION








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Engine Won't Choke not closing Check choke
Start operation, see
FUEL SYSTEMS
Choke linkage bent Check linkage, see
FUEL SYSTEM









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Engine Starts, Choke vacuum kick setting Check setting and
Then Dies too wide adjust see, FUEL
SYSTEMS
Fast idle RPM too low Reset RPM to specif-
ication, see TUNE-UP
Fast idle cam index Reset fast idle cam
incorrect index, see FUEL
SYSTEMS
Vacuum leak Inspect vacuum
system for leaks
Low fuel pump outlet Repair or replace
pump, see FUEL
SYSTEMS
Low carburetor fuel level Check float setting
see FUEL SYSTEM









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Engine Quits Choke vacuum kick setting Reset vacuum kick
Under Load incorrect setting,see FUEL
SYSTEMS
Fast idle cam index Reset fast idle cam
incorrect index, see FUEL
SYSTEM
Incorrect hot fast idle Reset fast idle RPM,
speed RPM see TUNE-UP









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Engine Starts, Choke vacuum kick set too Reset vacuum kick,
Runs Up,Then narrow see FUEL SYSTEMS
Idles, Slowly
With Black Smoke Fast idle cam index Reset fast idle cam

CONDITION POSSIBLE CAUSE CORRECTION








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Hesitation With Vacuum leak Inspect vacuum lines
Small Amount of
Gas Pedal Movement
Accelerator pump weak or Replace pump, see
inoperable FUEL SYSTEMS
Float level setting too low Reset float level,
see,FUEL SYSTEMS
Metering rods sticking or Inspect and/or
binding replace rods, see
FUEL SYSTEMS
Carburetor idle or transfer Inspect system and
system plugged remove restriction
Frozen or binding heated air Inspect heated air
inlet door for binding









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Hesitation With Defective accelerator pump Replace pump, see
Heavy Gas Pedal FUEL SYSTEMS
Movement
Metering rod carrier Remove restriction
sticking or binding
Large vacuum leak Inspect vacuum
system and repair
leak
Float level setting too Reset float level,
low see FUEL SYSTEMS
Defective fuel pump, lines Inspect pump, lines
or filter and filter
Air door setting incorrect Adjust air door
setting, see FUEL









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DIESEL ENGINE 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.
NOTE: Diesel engines mechanical diagnosis is the same as gasoline
engines for items such as noisy valves, bearings, pistons,
etc. The following trouble shooting covers only items
pertaining to diesel engines.
BASIC DIESEL ENGINE TROUBLE SHOOTING CHART









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CONDITION POSSIBLE CAUSE CORRECTION








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Engine Won't Bad battery connections Check connections
Crank or dead batteries and/or replace

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