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Online Manual Jeep > Jeep Cherokee XJ > 1984 - 1991 > TROUBLE SHOOTING - BASIC PROCEDURES > ENGINE PERFORMANCE

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


CONDITION POSSIBLE CAUSE CORRECTION


Engine Wont Choke not closing Check choke

Start operation, see

FUEL SYSTEMS

Choke linkage bent Check linkage, see

FUEL SYSTEM


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 specification, 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


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


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


incorrect index, see FUEL

SYSTEMS

Hot fast idle RPM too low Reset fast idle RPM,

see TUNE-UP

BASIC HOT START SYMPTOMS TROUBLE SHOOTING CHART


CONDITION POSSIBLE CAUSE CORRECTION


Engine Wont Engine flooded Allow fuel to

Start evaporate


BASIC COLD ENGINE DRIVEABILITY SYMPTOMS TROUBLE SHOOTING CHART
CONDITION POSSIBLE CAUSE CORRECTION


Engine Stalls in Choke vacuum kick setting Reset choke vacuum
Gear incorrect kick, see FUEL

SYSTEMS

Fast idle RPM incorrect Reset fast idle RPM,

see TUNE-UP

Fast idle cam index Reset fast idle cam

incorrect see FUEL SYSTEMS


Acceleration Sag Defective choke control Replace choke
or Stall switch control switch

Choke vacuum kick setting Reset choke vacuum
incorrect kick see, FUEL

SYSTEMS

Float level incorrect Adjust float level,
(too low) FUEL SYSTEMS

Accelerator pump defective Repair or replace

pump see FUEL SYSTEMS

Secondary throttles not Inspect lockout
closed adjustment,see FUEL

SYSTEMS


Sag or Stall Defective choke control Replace choke
After Warmup switch control switch, see

FUEL SYSTEMS

Defective accelerator pump Replace pump, see

FUEL SYSTEMS

Float level incorrect Adjust float level,
(too low) see FUEL SYSTEMS


Backfiring & Plugged heat crossover Remove restriction Black Smoke system


BASIC WARM ENGINE DRIVEABILITY SYMPTOMS TROUBLE SHOOTING CHART

CONDITION POSSIBLE CAUSE CORRECTION


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


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

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

CONDITION POSSIBLE CAUSE CORRECTION

Engine Wont 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

Engine Cranks Bad battery connections Check connections

Slowly, Wont or dead batteries and/or replace

Start batteries

Engine oil too heavy Replace engine oil

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

Engine Starts, Incorrect slow idle Reset idle adjustment,
Wont 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

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

mnnprf i nns

Air in fuel system Bleed air from system

Incorrect or contaminated Replace fuel fuel

Injector nozzle malfunction Check nozzles, see

FUEL SYSTEMS

Engines Starts Injection pump timing Reset pump timing, see

and Idles Rough incorrect FUEL SYSTEMS

W/out Smoke or Engine not fully broken in Put more miles on

Noise, But Clears engine

After Warm-Up Air in system Bleed air from system

Injector nozzle malfunction Check nozzles, see

FUEL SYSTEMS

Engine Idles Blocked fuel filter Replace fuel filter

Correctly, Injection pump timing Reset pump timing, see

Misfires Above incorrect FUEL SYSTEMS

Idle Incorrect or contaminated Replace fuel

fuel

Engine Wont Fast idle adjustment Reset fast idle, see
Return To Idle incorrect TUNE-UP

Internal injection pump Replace injection pump,
malfunction see FUEL SYSTEMS

External linkage binding Check linkage and

remove binding

Fuel Leaks On Loose or broken fuel line Check lines and

Ground connections

Internal injection pump Replace injection pump,

seal leak see FUEL SYSTEMS

Cylinder Injector nozzles sticking Test injectors, see

Knocking Noise open FUEL SYSTEMS

Very low nozzle opening Test injectors and/or

pressure replace

Loss of Engine Restricted air intake Remove restriction
Power EGR valve malfunction Replace EGR valve

Blocked or damaged exhaust Remove restriction
system and/or replace

components

Blocked fuel tank filter Replace filter Restricted fuel filter Remove restriction

and/or replace filter Block vent in gas cap Remove restriction

and/or replace cap

Tank-to-injection pump fuel Check fuel lines and
supply blocked connections

Blocked fuel return system Remove restriction Incorrect or contaminated Replace fuel fuel Blocked injector nozzles Check nozzle for

blockage, see FUEL

SYSTEMS
Low compression Check valves, rings,

pistons, see ENGINES

Loud Engine Basic timing incorrect Reset timing, see

Noise With Black FUEL SYSTEMS

Smoke EGR valve malfunction Replace EGR valve

Internal injection pump Replace injection pump,

malfunction see FUEL SYSTEMS

Incorrect injector pump Check pressure, see
housing pressure FUEL SYSTEMS

Engine Cooling system leaks Check cooling system

Overheating and repair leaks

Belt slipping or damaged Check tension and/or

replace belt

Thermostat stuck closed Remove and replace

thermostat, see ENGINE COOLING Head gasket leaking Replace head gasket

Oil Light on at Low oil pump pressure Check oil pump

Idle operation, see ENGINES

Oil cooler or line Remove restriction

restricted and/or replace cooler

Engine Wont Injector pump fuel solenoid Remove and check
Shut Off does not return fuel valve solenoid and replace
to OFF position if needed

VACUUM PUMP DIAGNOSIS

Excessive Noise Loose pump-to-drive Tighten screws assembly screws

Loose tube on pump assembly Tighten tube Valves not functioning Replace valves properly

Oil Leakage Loose end plug Tighten end plug

Bad seal crimp Remove and re-crimp

seal

FUEL INJECTION 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 FUEL INJECTION TROUBLE SHOOTING CHART

CONDITION POSSIBLE CAUSE CORRECTION

Engine Wont Cold start valve inoperative Test valve and
Start (Cranks circuit

Normally)

Poor connection;vacuum or Check vacuum and
wiring electrical

connections

Contaminated fuel Test fuel for water

or alcohol

Defective fuel pump relay Test relay and
or circuit wiring

Battery too low Charge and test

battery

Low fuel pressure Test pressure regul-

ator and fuel pump, check for restricted lines and filters

No distributor reference Repair ignition
pulses system as necessary

Open coolant temperature Test sensor and
sensor circuit wiring

Shorted W.O.T. switch in Disconnect W.O.T.
T.P.S. switch, engine

should start

Defective ECM Replace ECM

Fuel tank residual pressure Test for fuel
valve leaks pressure drop after

shut down

Hard Starting Disconnected hot air tube Reconnect tube and

to air cleaner test control valve

Defective Idle Air Control Test valve operation
(IAC) valve and circuit

Shorted, open or misadjusted Test and adjust or
T.P.S. replace T.P.S.

EGR valve open Test EGR valve and

control circuit

Poor Oxygen sensor signal Test for shorted or

circuit

Incorrect mixture from PCV Test PCV for flow,
system check sealing of oil

filter cap

Poor High Speed Low fuel pump volume Faulty pump or

Operation restricted fuel

lines or filters

Poor MAP sensor signal Test MAP sensor,

vacuum hose and wiring

Poor Oxygen sensor signal Test for shorted or

open sensor or circuit

Open coolant temperature Test sensor and
sensor circuit wiring

Faulty ignition operation Check wires for

cracks or poor connections, test secondary voltage with oscilloscope

Contaminated fuel Test fuel for water

or alcohol

Intermittent ECM ground Test ECM ground

connection for resistance

Restricted air cleaner Replace air cleaner

Restricted exhaust system Test for exhaust

manifold back pressure

Poor MAF sensor signal Check leakage

between sensor and manifold

Poor VSS signal If tester for ALCL

hook-up is available check that VSS reading matches speedometer

Ping or Knock on Poor Knock sensor signal Test for shorted or
Acceleration open sensor or

circuit

Poor Baro sensor signal Test for shorted or

open sensor or circuit

Improper ignition timing See VEHICLE EMISSION

CONTROL LABEL (where applicable)

Check for engine Low coolant, loose

overheating problems belts or electric

cooling fan inoperative

NOTE: For additional electronic fuel injection trouble shooting information, see the appropriate article in the ENGINE PERFORMANCE section (not all vehicles have Computer Engine Control articles). Information is provided there for diagnosing fuel system problems on vehicles with electronic fuel injection.

IGNITION 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.

Ignition Secondary Trouble Shooting Chart



STARTER 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 STARTER TROUBLE SHOOTING CHART


CONDITION POSSIBLE CAUSE CORRECTION


Starter Fails Dead battery or bad Check battery charge to Operate connections between and all wires and

starter and battery connections to starter

Ignition switch faulty Adjust or replace

or misadjusted ignition switch

Open circuit between Check and repair wires

starter switch ignition and connections as

terminal on starter relay necessary

Starter relay or starter See Testing in STARTER

defective article

Open solenoid pull-in See Testing in STARTER

wire article


Starter Does Not Weak battery or dead Charge or replace

Operate and cell battery as necessary
Headlights Dim

Loose or corroded battery Check that battery

connections connections are clean

and tight

Internal ground in See Testing in STARTER

starter windings article

Grounded starter fields See Testing in STARTERS

Armature rubbing on pole See STARTER article
shoes


Starter Turns Starter clutch slipping See STARTER article
but Engine
Does Not Rotate

Broken clutch housing See STARTER article

Pinion shaft rusted or See STARTER article
dry

Engine basic timing See Ignition Timing in

incorrect TUNE-UP article

Broken teeth on engine Replace flywheel and

flywheel check for starter pinion

gear damage


Starter Will Not Faulty overrunning See STARTER article
Crank Engine clutch

Broken clutch housing See STARTER article

Broken flywheel teeth Replace flywheel and

check for starter pinion gear damage

Armature shaft sheared See STARTER article

or reduction gear teeth

stripped

Weak battery Charge or replace

battery as necessary

Faulty solenoid See On-Vehicle Tests in

STARTER article

Poor grounds Check all ground

connections for tight and clean connections

Ignition switch faulty Adjust or replace
or misadjusted ignition switch as

necessary

Starter Cranks Battery weak or Charge or replace

Engine Slowly defective battery as necessary

Engine overheated See ENGINE COOLING

SYSTEM article

Engine oil too heavy Check that proper

viscosity oil is used

Poor battery-to-starter Check that all
connections between

battery and starter are clean and tight

Current draw too low or See Bench Tests in
too high STARTER article

Bent armature, loose pole See STARTER article

shoes screws or worn

bearings

Burned solenoid contacts Replace solenoid
Faulty starter Replace starter


Starter Engages Engine timing too far See Ignition Timing in
Engine Only advanced TUNE-UP article

Momentarily

Overrunning clutch not Replace overrunning
engaging properly clutch. See STARTER

article

Broken starter clutch See STARTER article

Broken teeth on engine Replace flywheel and
flywheel check starter pinion

gear for damage

Weak drive assembly See STARTER article thrust spring

Weak hold-in coil See Bench Tests in

STARTER article


Starter Drive Defective point assembly See Testing in STARTER
Will Not Engage article

Poor point assembly ground See Testing in STARTER

article

Defective pull-in coil Replace starter

solenoid

Starter Relay Dead battery Charge or replace

Does Not Close battery as necessary

Faulty wiring Check all wiring and

connections leading to relay

Neutral safety switch Replace neutral safety
faulty switch

Starter relay faulty Replace starter relay


Starter Drive Starter motor loose on Tighten starter

Will Not mountings attach bolts

Disengage

Worn drive end bushing See STARTER article

Damaged engine flywheel Replace flywheel and
teeth starter pinion gear for

damage

Drive yolk return spring Replace return spring broken or missing

Faulty ignition switch Replace ignition switch

Insufficient clearance Replace starter between winding leads to solenoid solenoid terminal and main contact in solenoid

Starter clutch not Replace starter clutch disengaging

Ignition starter switch Replace ignition switch contacts sticking


Starter Relay Faulty solenoid switch, Check all wiring
Operates but switch connections or between relay and
Solenoid Does Not solenoid or replace

relay or solenoid as necessary

Broken lead or loose Repair wire or wire soldered connections connections as

necessary

Solenoid Plunger Weak battery Charge or replace

Vibrates When battery as necessary
Switch is Engaged

Solenoid contacts Clean contacts or

corroded replace solenoid

Faulty wiring Check all wiring

leading to solenoid

Broken connections inside Repair connections or
switch cover replace solenoid

Open hold-in wire Replace solenoid

Replace brushes or brush springs as necessary

Low Current Draw Worn brushes or weak Replace brushes or

brush springs as


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

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

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


CONDITION POSSIBLE CAUSE CORRECTION


Normal Spark Light Tan or Gray deposits No Action Plug Condition

Electrode not burned or No Action

fouled

Gap tolerance not changed No Action


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


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

Excessive cylinder wear Rebore or replace

block

Excessive valve guide Worn or loose bearing clearance


Gap Bridged Deposits in combustion Clean combustion

chamber becoming fused chamber of deposits to electrode


Blistered Engine overheating Check cooling system

Electrode

Wrong type of fuel Replace with correct

fuel

Loose spark plugs Retighten spark plugs

Over-advanced ignition Reset ignition timing
timing see ENGINE PERFORMANCE


Pre-Ignition or Incorrect type of fuel Replace with correct
Melted Electrodes fuel

Incorrect ignition timing Reset ignition timing

see ENGINE PERFORMANCE

Burned valves Replace valves

Engine Overheating Check cooling system

Wrong type of spark plug, Replace with correct
too hot spark plug, see

ENGINE PERFORMANCE


Chipped Severe detonation Check for over-

Insulators advanced timing or

combustion

Improper gapping Re-gap spark plugs

procedure


Rust Colored Additives in unleaded Try different fuel
Deposits fuel brand


Water In Combus- Blown head gasket or Repair or replace
tion Chamber cracked head head or head gasket


NOTE: Before diagnosing an electronic ignition system, ensure that all wiring is connected properly between distributor, wiring connector and spark plugs. Ignition problem will show up either as: Engine Will Not Start or Engine Runs Rough.

BASIC ELECTRONIC IGNITION TROUBLE SHOOTING CHARTS
CONDITION POSSIBLE CAUSE CORRECTION


Engine Wont Open circuit between Repair circuit
Start distributor and bulkhead

connector

Open circuit between Repair circuit bulkhead connector and

ignition switch

Open circuit between Repair circuit
ignition switch and
starter solenoid


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


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


BASIC ELECTRONIC IGNITION TROUBLE SHOOTING CHARTS - USING OSCILLOSCOPE PATTERNS


CONDITION POSSIBLE CAUSE CORRECTION


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


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

repair


One or More, But Carburetor idle mixture Readjust carburetor,

Not All Firing not balanced see ENGINE PERFORMANCE
Voltage Lines are

Higher Than Others EGR valve stuck open Clean and/or replace

valve

High resistance in spark Replace spark plug

plug wires wires

Cracked or broken spark Replace spark plugs
plug insulator

Intake vacuum leak Repair leak

Defective spark plugs Replace spark plugs

Corroded spark plug Replace spark plugs
terminals


One or More, But Curb idle mixture not Readjust carburetor,

Not All Firing balanced see ENGINE PERFORMANCE
Voltage Lines Are

Lower Than Others Breaks in plug wires Replace plug wires

causing arcing

Cracked coil tower causing Replace coil
arcing

Low compression Determine cause and

repair

Defective spark plugs Replace spark plugs

Corroded spark plugs Replace spark plugs


Cylinders Not Cracked distributor cap Replace distributor

Firing terminals cap

Shorted spark plug wire Determine cause and

repair

Mechanical problem in Determine cause and

engine repair

Defective spark plugs Replace spark plugs

Spark plugs fouled Replace spark plugs


BASIC DRIVEABILITY PROBLEMS TROUBLE SHOOTING TABLE


CONDITION POSSIBLE CAUSE CORRECTION


Hard Starting Binding carburetor linkage Eliminate binding

Binding choke linkage Eliminate binding

Binding choke piston Eliminate binding

Restricted choke vacuum Check vacuum lines

for blockage

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


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


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


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


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


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


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

Vacuum leaks Repair vacuum leaks

Fuel lines clogged Remove restriction


Hesitation Cracked or broken vacuum Replace vacuum hoses

hoses

Vacuum leaks Repair Vacuum leaks

Binding carburetor linkage Eliminate binding

Binding throttle linkage Eliminate binding

Binding choke linkage or Eliminate binding
fast idle cam

Improper float setting Readjust float

setting, see FUEL

Cracked or broken ignition Replace ignition

wires wires


Rough idle, Incorrect curb idle or fast Reset idle speed, see

Missing or idle speed see ENGINE PERFORMANCE
Stalling

Incorrect basic timing Reset ignition timing

see ENGINE PERFORMANCE

Improper idle mixture Reset idle mixture,

adjustment see ENGINE PERFORMANCE

Improper feedback system Check feedback system

operation see ENGINE PERFORMANCE

Incorrect spark plug gap Reset spark plug gap,

see ENGINE PERFORMANCE

Moisture in ignition Dry components
components

Loose or broken ignition Replace ignition

wires wires

Damaged distributor cap or Replace distributor

or rotor cap or rotor

Faulty ignition coil Replace ignition coil

Fuel filter clogged or worn Replace fuel filter

Damaged idle mixture screw Replace idle mixture

screw, see FUEL

Improper fast idle cam Reset fast idle cam

adjustment adjustment, see TUNE-

see ENGINE PERFORMANCE

Improper EGR valve operation Replace EGR valve

Faulty PCV valve air flow Replace PCV valve

Choke binding or improper Reset choke or

choke setting eliminate binding

Vacuum leak Repair vacuum leak

Improper float bowl fuel Reset float

level adjustment, see FUEL

Clogged air bleed or idle Clean carburetor

passages passages, see FUEL

Clogged or worn air cleaner Replace air filter
filter

Faulty choke vacuum Replace diaphragm,

diaphragm see ENGINE PERFORMANCE

Exhaust manifold heat valve Replace heat valve
inoperative

Improper distributor spark Check distributor

advance operation

Leaking valves or valve Check and repair

components valvetrain

Improper carburetor Remove and remount

mounting carburetor

Excessive play in Replace distributor
distributor shaft

Loose or corroded wiring Repair or replace as

connections required

Engine Surges Improper PCV valve airflow Replace PCV valve

Vacuum leaks Repair vacuum leaks

Clogged air bleeds Remove restriction

EGR valve malfunction Replace EGR valve

Restricted air cleaner Replace air filter
filter

Cracked or broken vacuum Replace vacuum hoses
hoses

Cracked or broken ignition Replace ignition

wires wires

Vacuum advance malfunction Check unit and

replace as necessary

Defective or fouled spark Replace spark plugs
plugs

Ping or Spark Incorrect ignition timing Reset ignition timing

Knock see ENGINE PERFORMANCE

Distributor centrifugal or Check operation and

vacuum advance malfunction replace as necessary

Carburetor setting too lean Readjust mixture

Carburetor setting too lean Readjust mixture

setting, see ENGINE PERFORMANCE

Vacuum leak Eliminate vacuum leak

EGR valve malfunction Replace EGR valve

Poor Gasoline Cracked or broken vacuum Replace vacuum hoses
Mileage hoses

Vacuum leaks Repair vacuum leaks

Defective ignition wires Replace wires

Incorrect choke setting Readjust setting, see

ENGINE PERFORMANCE

Defective vacuum advance Replace vacuum advance Defective spark plugs Replace spark plugs

Binding carburetor power Eliminate binding piston

Dirt in carburetor jets Clean and/or replace

jets

Incorrect float adjustment Readjust float

setting, see FUEL

Defective power valve Replace power valve,

see ENGINE PERFORMANCE

Incorrect idle speed Readjust idle speed Engine Stalls Improper float level Readjust float level

Leaking needle valve and Replace needle valve
seat and seat

Vacuum leaks Eliminate vacuum

leaks

VACUUM PUMP - DIESEL 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.

VACUUM PUMP (DIESEL) TROUBLE SHOOTING CHART

CONDITION POSSIBLE CAUSE CORRECTION

Excessive Noise Loose pump-to-drive Tighten screws assembly screws

Loose tube on pump assembly Tighten tube Valves not functioning Replace valves properly

Oil Leakage Loose end plug Tighten end plug

Bad seal crimp Remove and re-crimp

seal

MANUAL TRANSMISSION

MANUAL TRANSMISSION 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.

MANUAL TRANSMISSION/TRANSAXLE TROUBLE SHOOTING
Condition Possible Cause

Noisy In Forward Gears .Low gear oil level,

.Loose bell housing bolts, .Worn bearings or gears

Clunk On Deceleration

(FWD Only) .Loose engine mounts,

.Worn inboard CV joints, .Worn differential pinion shaft, .Side gear hub counterbore in case worn oversize

Gear Clash When Shifting

Forward Gears .Clutch Out Of Adjustment,

.Shift linkage damaged or out of adjustment, .Gears or synchronizers damaged, .Low gear oil level

Transmission Noisy When

Moving (RWD Only) Quiet In

Neutral With Clutch Engaged .Worn rear outputshaft bearing

Gear Rattle .Worn bearings,

.Wrong gear oil, .Low gear oil, .Worn gears

Steady Ticking At Idle
(Increases With RPM) .Broken tooth on gear

Gear Clash When Shifting

Forward Gears .Worn or broken synchronizers

Loud Whine In Reverse .Normal condition (1)

Noise When Stepping On Clutch .Bad release bearing,

.Worn pilot bearing

Ticking Or Screeching As

Clutch Is Engaged .Faulty release bearing,

.Uneven pressure plate fingers

Click Or Snap When Clutch

Is Engaged .Worn clutch fork,

.Worn or broken front bearing retainer

Transmission Shifts Hard .Clutch not releasing,

.Shift mechanism binding, .Clutch installed backwards

Will Not Shift Into One Gear, Shifts Into All

Others .Bent shift fork,

.Worn detent balls

Locked Into Gear,

Cannot Shift .Clutch adjustment,

.Worn detent balls

Transmission Jumps Out

Of Gear .Pilot bearing worn,

.Bent shift fork, .Worn gear teeth or face .Excessive gear train end play .Worn synchronizers .Missing detent ball spring .Shift mechanism worn or out of adjustment

.Engine or transmission mount bolts loose or out of adjustment .Transmission not aligned

Shift Lever Rattle .Worn shift lever or detents

.Worn shift forks .Worn synchronizers sleeve

Shift Lever Hops Under

Acceleration .Worn engine or transmission

mounts

(1) - Most units use spur cut gears in reverse and are noisy