spark plugs replace JEEP YJ 1995 Service And Repair Manual

MAINTENANCE SCHEDULES
INTRODUCTION
There are two maintenance schedules that show
proper service intervals for Jeep Cherokee and Jeep
Wrangler vehicles. Use the schedule that best de-
scribes the conditions the vehicle is operated under.
When mileage and time is listed, follow the interval
that occurs first.
ScheduleÐAlists all the scheduled maintenance
to be performed under normal operating conditions.
ScheduleÐBis a schedule for vehicles that are
usually operated under one or more of the following
conditions.
²Frequent short trip driving less than 5 miles (8
km).
²Frequent driving in dusty conditions.
²Trailer towing or heavy load hauling.
²Frequent long periods of engine idling.
²Sustained high speed operation.
²Desert operation.
²Frequent starting and stopping.
²Cold climate operation.
²Off road driving.
²Commercial service.
²Snow plow operation.
²More than half of vehicle operation occurs in
heavy city traffic during hot weather (above 90É F).
AT EACH STOP FOR GASOLINE
²Check engine oil level and add as required.
²Check windshield washer solvent and add as re-
quired.
ONCE A MONTH
²Check tire pressure and look for unusual tire wear
or damage.
²Check fluid levels of coolant reservoir, brake mas-
ter cylinder, power steering and transmission. Add
fluid as required.
²Check all lights and other electrical items for cor-
rect operation.
²Inspect battery and clean and tighten terminals as
required.
²Check rubber seals on each side of the radiator for
proper fit.
AT EACH OIL CHANGE
²Inspect exhaust system.
²Inspect brake hoses.
²Rotate the tires at each oil change interval shown
on ScheduleÐA: (7,500 Miles) or every other interval
shown on ScheduleÐB: (6,000 Miles).
²Check engine coolant level, hoses, and clamps.
²Lubricate 4x4 steering linkage.
²Lubricate propeller shaft universal joints and slip
spline, if equipped.After completion of off-road (4WD) operation, the
underside of the vehicle should be thoroughly in-
spected. Examine threaded fasteners for looseness.
HARSH SURFACE ENVIRONMENTS
After vehicle operation in a harsh surface environ-
ment, the following components should be inspected
and cleaned as soon as possible:
²Brake drums.
²Brake linings.
²Front wheel bearings (2WD vehicles only).
²Axle coupling joints.
This will prevent wear and/or unpredictable brake
action.
EMISSION CONTROL SYSTEM MAINTENANCE
The schedule emission maintenance listed inbold
typeon the following schedules, must be done at the
mileage specified to assure the continued proper
functioning of the emission control system. These,
and all other maintenance services included in this
manual, should be done to provide the best vehicle
performance and reliability. More frequent mainte-
nance may be needed for vehicles in severe operating
conditions such as dusty areas and very short trip
driving.
SCHEDULEÐA
7,500 MILES (12 000 KM) OR AT 6 MONTHS
²Change engine oil.
²Replace engine oil filter.
²Lubricate steering linkage (4x4).
15,000 MILES (24 000 KM) OR AT 12 MONTHS
²Change engine oil.
²Replace engine oil filter.
²Lubricate steering linkage.
22,500 MILES (36 000 KM) OR AT 18 MONTHS
²Change engine oil.
²Replace engine oil filter.
²Lubricate steering linkage (4x4).
²Inspect brake linings.
30,000 MILES (48 000 KM) OR AT 24 MONTHS
²Replace air cleaner element.
²Replace spark plugs.
²Adjust belt tension on non-automatic tensioning
drive belts.
²Change engine oil.
²Replace engine oil filter.
²Lubricate steering linkage.
²Drain and refill automatic transmission.
²Drain and refill transfer case.
0 - 4 LUBRICATION AND MAINTENANCEJ

37,500 MILES (60 000 KM) OR AT 30 MONTHS
²Change engine oil.
²Replace engine oil filter.
²Lubricate steering linkage (4x4).
²Drain and refill manual transmission.
45,000 MILES (72 500 KM) OR AT 36 MONTHS
²Change engine oil.
²Replace engine oil filter.
²Lubricate steering linkage.
²Inspect brake linings.
²Flush and replace engine coolant, regardless of
mileage.
52,500 MILES (84 500 KM) OR AT 42 MONTHS
²Change engine oil.
²Replace engine oil filter.
²Lubricate steering linkage (4x4).
²Flush and replace engine coolant if not done at 36
months.
60,000 MILES (96 500 KM) OR AT 48 MONTHS
²Replace air cleaner element.
²Replace distributor cap and rotor.
²Replace ignition wires.
²Replace spark plugs.
²Adjust or replace drive belts.
²Change engine oil.
²Replace engine oil filter.
²Replace fuel filter. (See Note #1)
²Lubricate steering linkage.
²Drain and refill automatic transmission.
²Drain and refill transfer case.
67,500 MILES (108 500 KM) OR AT 54
MONTHS
²Change engine oil.
²Replace engine oil filter.
²Lubricate steering linkage (4x4).
²Inspect brake linings.
75,000 MILES (120 500 KM) OR AT 60
MONTHS
²Change engine oil.
²Replace engine oil filter.
²Lubricate steering linkage.
²Drain and refill manual transmission.
²Flush and replace engine coolant if it has been
30,000 miles (48 000 km) or 24 months since last
change.
82,500 MILES (133 000 KM) OR AT 66
MONTHS
²Change engine oil.
²Replace engine oil filter.
²Lubricate steering linkage (4x4).²Flush and replace engine coolant if it has been
30,000 miles (48 000 km) or 24 months since last
change.
90,000 MILES (145 000 KM) OR AT 72
MONTHS
²Replace air cleaner element.
²Replace spark plugs.
²Adjust drive belts.
²Change engine oil.
²Replace engine oil filter.
²Lubricate steering linkage.
²Inspect brake linings.
²Drain and refill automatic transmission.
²Drain and refill transfer case.
97,500 MILES (157 000 KM) OR AT 78
MONTHS
²Change engine oil.
²Replace engine oil filter.
²Lubricate steering linkage (4x4).
105,000 MILES (169 000 KM) OR AT 84
MONTHS
²Change engine oil.
²Replace engine oil filter.
²Lubricate steering linkage.
²Flush and replace engine coolant if it has been
30,000 miles (48 000 km) or 24 months since last
change.
112,500 MILES (181 000 KM) OR AT 90
MONTHS
²Change engine oil.
²Replace engine oil filter.
²Lubricate steering linkage (4x4).
²Inspect brake linings.
²Drain and refill manual transmission.
²Flush and replace engine coolant if it has been
30,000 miles (48 000 km) or 24 months since last
change.
120,000 MILES (193 000 KM) OR AT 96
MONTHS
²Replace air cleaner element.
²Replace distributor cap and rotor.
²Lubricate steering linkage.
²Drain and refill automatic transmission.
²Drain and refill transfer case.
²Replace ignition wires.
²Replace spark plugs.
²Adjust or replace drive belts.
²Change engine oil.
²Replace engine oil filter.
²Replace fuel filter. (See note #1)
JLUBRICATION AND MAINTENANCE 0 - 5

SCHEDULEÐB
3,000 MILES (4 800KM)
²Change engine oil.
²Replace engine oil filter.
6,000 MILES (9 600KM)
²Change engine oil.
²Replace engine oil filter.
²Lubricate steering linkage (4x4).
9,000 MILES (14 400KM)
²Change engine oil.
²Replace engine oil filter.
12,000 MILES (19 200KM)
²Change engine oil.
²Replace engine oil filter.
²Drain and refill automatic transmission.
²Change front and rear axle fluid.*
²Lubricate steering linkage (4x4).
²Inspect brake linings.
15,000 MILES (24 000KM)
²Change engine oil.
²Replace engine oil filter.
²Lubricate steering linkage (4x2).
²Inspect air cleaner element, replace as necessary.
18,000 MILES (29 000KM)
²Change engine oil.
²Replace engine oil filter.
²Drain and refill Manual transmission fluid.
²Lubricate steering linkage (4x4).
21,000 MILES (34 000KM)
²Change engine oil.
²Replace engine oil filter.
24,000 MILES (38 000KM)
²Change engine oil.
²Replace engine oil filter.
²Lubricate steering linkage (4x4).
²Drain and refill automatic transmission.
²Change front and rear axle fluid.*
²Inspect brake linings.
²Inspect front wheel bearings, Clean and repack if
required (4x2).
27,000 MILES (43 000KM)
²Change engine oil.
²Replace engine oil filter.
30,000 MILES (48 000KM)
²Change engine oil.
²Replace engine oil filter.
²Lubricate steering linkage joints.
²Replace spark plugs.
²Replace air cleaner element.²Adjust drive belts.
²Drain and refill transfer case fluid.
33,000 MILES (53 000KM)
²Change engine oil.
²Replace engine oil filter.
36,000 MILES (58 000KM)
²Change engine oil.
²Replace engine oil filter.
²Lubricate steering linkage (4x4).
²Drain and refill automatic transmission.
²Drain and refill manual transmission fluid.
²Change front and rear axle fluid.*
²Inspect brake linings.
39,000 MILES (62 000KM)
²Change engine oil.
²Replace engine oil filter.
42,000 MILES (67 000KM)
²Change engine oil.
²Replace engine oil filter.
²Lubricate steering linkage (4x4).
45,000 MILES (72 000KM)
²Change engine oil.
²Replace engine oil filter.
²Lubricate steering linkage (4x2).
²Inspect air cleaner element, replace as necessary.
48,000 MILES (77 000KM)
²Change engine oil.
²Replace engine oil filter.
²Lubricate steering linkage (4x4).
²Drain and refill automatic transmission.
²Change front and rear axle fluid.*
²Inspect brake linings.
51,000 MILES (82 000KM)
²Change engine oil.
²Replace engine oil filter.
²Flush and replace engine coolant.
54,000 MILES (86 400KM)
²Change engine oil.
²Replace engine oil filter.
²Lubricate steering linkage (4x4).
²Drain and refill Manual transmission fluid.
57,000 MILES (91 000KM)
²Change engine oil.
²Replace engine oil filter.
60,000 MILES (96 000KM)
²Change engine oil.
²Replace engine oil filter.
²Lubricate steering linkage joints.
²Replace spark plugs.
0 - 6 LUBRICATION AND MAINTENANCEJ

²Drain and refill automatic transmission fluid.
²Change front and rear axle fluid.*
²Replace air cleaner element.
²Replace distributor cap and rotor.
²Replace ignition wires.
²Adjust or replace drive belts.
²Replace fuel filter. See note #1.
²Inspect brake linings.
²Drain and refill transfer case.
63,000 MILES (102 000KM)
²Change engine oil.
²Replace engine oil filter.
66,000 MILES (105 600KM)
²Change engine oil.
²Replace engine oil filter.
²Lubricate steering linkage (4x4).
69,000 MILES (110 000KM)
²Change engine oil.
²Replace engine oil filter.
72,000 MILES (115 200KM)
²Change engine oil.
²Replace engine oil filter.
²Lubricate steering linkage (4x4).
²Drain and refill Manual transmission fluid.
²Drain and refill automatic transmission.
²Change front and rear axle fluid.*
²Inspect brake linings.
75,000 MILES (120 000KM)
²Change engine oil.
²Replace engine oil filter.
²Lubricate steering linkage (4x2).
²Inspect air cleaner element, replace as necessary.
78,000 MILES (125 000KM)
²Change engine oil.
²Replace engine oil filter.
²Lubricate steering linkage (4x4).
81,000 MILES (130 000KM)
²Change engine oil.
²Replace engine oil filter.
²Flush and replace engine coolant.
84,000 MILES (134 400KM)
²Change engine oil.
²Replace engine oil filter.
²Lubricate steering linkage (4x4).
²Drain and refill automatic transmission fluid.
²Change front and rear axle fluid.*
²Inspect brake linings.
87,000 MILES (140 000KM)
²Change engine oil.
²Replace engine oil filter.
90,000 MILES (144 000KM)
²Change engine oil.
²Replace engine oil filter.
²Lubricate steering linkage.
²Replace spark plugs.
²Drain and refill Manual transmission fluid.
²Replace air cleaner element.
²Adjust drive belts.
²Drain and refill transfer case fluid.
93,000 MILES (149 000KM)
²Change engine oil.
²Replace engine oil filter.
96,000 MILES (154 000KM)
²Change engine oil.
²Replace engine oil filter.
²Lubricate steering linkage (4x4).
²Drain and refill automatic transmission fluid.
²Change front and rear axle fluid.*
²Inspect brake linings.
99,000 MILES (158 400KM)
²Change engine oil.
²Replace engine oil filter.
102,000 MILES (163 000KM)
²Change engine oil.
²Replace engine oil filter.
²Lubricate steering linkage (4x4).
105,000 MILES (168 000KM)
²Change engine oil.
²Replace engine oil filter.
²Inspect air cleaner element, replace as necessary.
²Lubricate steering linkage (4x2).
108,000 MILES (172 800KM)
²Change engine oil.
²Replace engine oil filter.
²Lubricate steering linkage (4x4).
²Drain and refill Manual transmission fluid.
²Drain and refill automatic transmission fluid.
²Change front and rear axle fluid.*
²Inspect brake linings.
111,000 MILES (177 600KM)
²Change engine oil.
²Replace engine oil filter.
²Flush and replace engine coolant.
114,000 MILES (182 400KM)
²Change engine oil.
²Replace engine oil filter.
²Lubricate steering linkage (4x4).
117,000 MILES (187 200KM)
²Change engine oil.
²Replace engine oil filter.
JLUBRICATION AND MAINTENANCE 0 - 7

120,000 MILES (192 000KM)
²Change engine oil.
²Replace engine oil filter.
²Lubricate steering linkage.
²Replace spark plugs.
²Drain and refill automatic transmission fluid.
²Change front and rear axle fluid.*
²Inspect brake linings.
²Replace air cleaner element.
²Replace distributor cap and rotor.
²Replace ignition wires.
²Adjust or replace drive belts.
²Replace fuel filter. See note #1.²Drain and refill transfer case fluid.
NOTE 1:Not required for California vehicles, rec-
ommended for proper vehicle performance.
* Off-highway operation, trailer towing, taxi, limou-
sine, bus, snow plowing, or other types of commercial
service or prolonged operation with heavy loading,
especially in hot weather, require front and rear axle
service indicated witha*inScheduleÐB. Perform
these services if you usually operate your vehicle un-
der these conditions.
Inspection and service should also be performed
anytime a malfunction is observed or suspected.
0 - 8 LUBRICATION AND MAINTENANCEJ

ENGINE MAINTENANCE
INDEX
page page
Accessory Drive Belt....................... 21
Air Cleaner Element....................... 18
Air-Conditioner Compressor.................. 21
Battery................................. 20
Crankcase Ventilation System................ 19
Emission Control System................... 20
Engine Break-In.......................... 15
Engine Cooling System..................... 18
Engine Oil.............................. 15Engine Oil Change and Filter Replacement...... 16
Engine Oil Filter.......................... 17
Engine Supports.......................... 21
Exhaust System.......................... 21
Fuel Filter............................... 19
Fuel Usage StatementÐGas Engines.......... 19
Ignition Cables, Distributor Cap and Rotor....... 20
Rubber and Plastic Component Inspection....... 20
Spark Plugs............................. 20
ENGINE BREAK-IN
CAUTION: Wide open throttle operation in low
gears, before engine break-in period is complete,
can damage engine.
After first starting a new engine, allow it to idle for
15 seconds before shifting into a drive gear. Also:
²Drive the vehicle at varying speeds less than 88
km/h (55 mph) for the first 480 km (300 miles).
²Avoid fast acceleration and sudden stops.
²Do not drive at full-throttle for extended periods of
time.
²Do not drive at constant speeds.
²Do not idle the engine excessively.
A special break-in engine oil is not required. The
original engine oil installed is a high quality, energy
conserving lubricant. Special break-in oils are not
recommended. These oils could interfere with the
normal piston ring seating process.
New engines tend to consume more fuel and oil un-
til after the break-in period has ended.
ENGINE OIL
WARNING: NEW OR USED ENGINE OIL CAN BE IR-
RITATING TO THE SKIN. AVOID PROLONGED OR
REPEATED SKIN CONTACT WITH ENGINE OIL.
CONTAMINANTS IN USED ENGINE OIL, CAUSED BY
INTERNAL COMBUSTION, CAN BE HAZARDOUS TO
YOUR HEALTH. THOROUGHLY WASH EXPOSED
SKIN WITH SOAP AND WATER.
DO NOT WASH SKIN WITH GASOLINE, DIESEL
FUEL, THINNER, OR SOLVENTS, HEALTH PROB-
LEMS CAN RESULT.
DO NOT POLLUTE, DISPOSE OF USED ENGINE
OIL PROPERLY. CONTACT YOUR DEALER OR GOV-
ERNMENT AGENCY FOR LOCATION OF COLLEC-
TION CENTER IN YOUR AREA.
ENGINE OIL SPECIFICATION
CAUTION: Do not use non-detergent or straight
mineral oil when adding or changing crankcase lu-
bricant. Engine failure can result.
API SERVICE GRADE CERTIFIED
Use an engine oil that is API Service Grade Certi-
fied or an oil that conforms to the API Service Grade
SH or SH/CD. MOPAR provides engine oils that con-
form to all of these service grades.
SAE VISCOSITY
An SAE viscosity grade is used to specify the vis-
cosity grade of engine oil. SAE 30 specifies a single
viscosity engine oil. Engine oils also have multiple
viscosities. These are specified with a dual SAE vis-
cosity grade which indicates the cold-to-hot tempera-
ture viscosity range. Select an engine oil that is best
suited to your particular temperature range and vari-
ation (Fig.1).
ENERGY CONSERVING OIL
An Energy Conserving type oil is recommeded for
gasoline engines. They are designated as either EN-
ERGY CONSERVING or ENERGY CONSERVING
II.
Fig. 1 Temperature/Engine Oil Viscosity
JLUBRICATION AND MAINTENANCE 0 - 15

line. You may encounter fuels containing 3 percent or
more methanol along with other alcohols called cosol-
vents.
Problems that are the result of using methanol/gas-
oline blends are not the responsibility of Chrysler
Corporation. They may not be covered by the vehicle
warranty.
MTBE/ETBE
Gasoline and MTBE (Methyl Tertiary Butyl Ether)
blends are a mixture of unleaded gasoline and up to
15 percent MTBE. Gasoline and ETBE (Ethyl Ter-
tiary Butyl Ether) are blends of gasoline and up to
17 percent ETBE. Gasoline blended with MTBE or
ETBE may be used.
CLEAN AIR GASOLINE
Many gasolines are now being blended that con-
tribute to cleaner air, especially in those areas of the
country where air pollution levels are high. These
new blends provide a cleaner burning fuel and some
are referred to asReformulated Gasoline.
In areas of the country where carbon monoxide lev-
els are high, gasolines are being treated with oxygen-
ated materials such as MTBE, ETBE and ethanol.
Chrysler Corporation supports these efforts toward
cleaner air and recommends the use of these gaso-
lines as they become available.
IGNITION CABLES, DISTRIBUTOR CAP AND
ROTOR
Inspect and test ignition cables, distributor cap and
rotor when the spark plugs are replaced. Oil and
grime should be cleaned from the ignition cables and
distributor cap to avoid possible spark plug fouling.
Mopar Foamy Engine Degreaser or equivalent is rec-
ommended for cleaning the engine compartment. For
proper service and diagnostic procedures refer to
Group 8D, Ignition System.
IGNITION TIMING
The ignition timing for 2.5L and 4.0L engines is
not adjustable. Refer to the specifications listed on
the engine Emission Control Information Label. Re-
fer to Group 25, Emission Control Systems for addi-
tional information.
SPARK PLUGS
Ignition spark plugs should be replaced at the
mileage interval described in the Lubrication and
Maintenance Schedules. Refer to the General Infor-
mation section of this group. For proper service pro-
cedures refer to Group 8D, Ignition Systems.
BATTERY
WARNING: WEAR SAFETY GLASSES, RUBBER
GLOVES AND PROTECTIVE CLOTHING WHEN HAN-DLING/SERVICING A BATTERY. THE BATTERY
ELECTROLYTE CONTAINS SULFURIC ACID AND
WILL CAUSE HARM IF IT CONTACTS SKIN, EYES
OR CLOTHING. IT WILL ALSO DAMAGE PAINTED
(AS WELL AS UN-PAINTED) SURFACES OF A VEHI-
CLE. IF SULFURIC ACID CONTACTS ANY OF
THESE, FLUSH IMMEDIATELY WITH LARGE
AMOUNTS OF WATER. IF SULFURIC ACID CON-
TACTS SKIN OR EYES, GET IMMEDIATE MEDICAL
ATTENTION. DO NOT SMOKE IN THE VICINITY OF A
BATTERY. KEEP OPEN FLAMES AND SPARKS
AWAY FROM BATTERY FILLER CAPS BECAUSE
EXPLOSIVE GAS IS ALWAYS PRESENT.
Inspect battery tray, hold down and terminal con-
nections when other under hood service is performed.
For proper diagnostic procedures refer to Group 8A,
Battery/Starting/Charging System Diagnostics. For
service and cleaning procedures refer to Group 8B,
Battery/Starter Service.
Care should be taken when disposing a bat-
tery after removal from a vehicle. Lead-acid
batteries are highly poisonous and, when indis-
criminately disposed, could create a problem
for the environment. Contact the applicable lo-
cal city or county government agency to deter-
mine where automobile (lead-acid) batteries
can be properly disposed in the local area.
RUBBER AND PLASTIC COMPONENT INSPECTION
CAUTION: Plastic hoses or wire harness covers will
melt or deform when exposed to heat from exhaust
system or engine manifolds.
Position plastic or rubber components away from
moving parts in engine compartment or under vehi-
cle, or damage will result.
Do not allow rubber engine mounts or other com-
ponents to become oil contaminated, repair cause
of oil contamination and clean area.
All rubber and plastic components should be in-
spected when engine compartment or under vehicle
service is performed. When evidence of deterioration
exists, replacement is required. To reduce deteriora-
tion of rubber components, Chrysler Corporation rec-
ommends Mopar Foamy Engine Degreaser or
equivalent be used to clean engine compartment of
oil and road grime.
EMISSION CONTROL SYSTEM
Inspect all emission control components and hoses
when other under hood service is performed. Refer to
emission system Vacuum Hose Label located on the
inside of the hood in the engine compartment and
Group 25, Emission Control Systems for proper ser-
vice procedures.
0 - 20 LUBRICATION AND MAINTENANCEJ

CAUTION: Do not operate the engine with a spark
plug shorted for more than a minute. The catalytic
converter may be damaged.
Isolate the compression leak by shorting each
spark plug to the cylinder block. The gauge pointer
should stop or decrease vibration when spark plug
for leaking cylinder is shorted. This happens because
of the absence of combustion pressure.
COMBUSTION LEAKAGE TEST (WITHOUT
PRESSURE TESTER)
DO NOT WASTE reusable coolant. If the solution
is clean, drain the coolant into a clean container for
reuse.
WARNING: DO NOT REMOVE THE CYLINDER
BLOCK DRAIN PLUGS OR LOOSEN THE RADIATOR
DRAINCOCK WITH THE SYSTEM HOT AND UNDER
PRESSURE. SERIOUS BURNS FROM COOLANT
CAN OCCUR.
Drain sufficient coolant to allow for thermostat re-
moval. Refer to Thermostat Replacement. Disconnect
the water pump drive belt.
Disconnect the upper radiator hose from the ther-
mostat housing. Remove the housing and thermostat.
Install the thermostat housing.
Add coolant to the radiator to bring the level to
within 6.3 mm (1/4 in) of the top of the thermostat
housing.
CAUTION: Avoid overheating. Do not operate the
engine for an excessive period of time. Open the
draincock immediately after the test to eliminate
boil over of coolant.
Start the engine and accelerate rapidly three times
(to approximately 3000 rpm) while observing the
coolant. If internal engine combustion gases are leak-
ing into the cooling system, bubbles will appear in
the coolant. If bubbles do not appear, there is no in-
ternal combustion gas leakage.
COOLANT RESERVE/OVERFLOW SYSTEM
The system works along with the radiator pressure
cap. This is done by using thermal expansion and
contraction of the coolant to keep the coolant free of
trapped air. It provides:
²A volume for coolant expansion and contraction.
²A convenient and safe method for checking/adjust-
ing coolant level at atmospheric pressure. This is
done without removing the radiator pressure cap.
²Some reserve coolant to the radiator to cover mi-
nor leaks and evaporation or boiling losses.
As the engine cools, a vacuum is formed in the
cooling system of both the radiator and engine. Cool-ant will then be drawn from the coolant tank and re-
turned to a proper level in the radiator.
The coolant reserve/overflow system consists of a
radiator mounted pressurized cap, a plastic reserve/
overflow tank (Figs. 22, 23 or 24), a tube (hose) con-
necting the radiator and tank, and an overflow tube
on the side of the tank.
Fig. 22 Reserve/Overflow TankÐYJ Models
Fig. 23 Reserve/Overflow TankÐXJ ModelsÐExcept
Right Hand Drive
7 - 24 COOLING SYSTEM SERVICE PROCEDURESJ

For diagnostics, refer to the appropriate Powertrain
Diagnostic Procedures service manual for operation
of the DRB scan tool.
SPARK PLUGS
For spark plug removal, cleaning, gap adjustment
and installation, refer to the Component Removal/In-
stallation section of this group.
Faulty carbon and/or gas fouled plugs generally
cause hard starting, but they will clean up at higher
engine speeds. Faulty plugs can be identified in a
number of ways: poor fuel economy, power loss, de-
crease in engine speed, hard starting and, in general,
poor engine performance.
Remove the spark plugs and examine them for
burned electrodes and fouled, cracked or broken por-
celain insulators. For identification, keep plugs ar-
ranged in the order in which they were removed from
the engine. An isolated plug displaying an abnormal
condition indicates that a problem exists in the cor-
responding cylinder. Replace spark plugs at the inter-
vals recommended in the maintenance chart in
Group 0, Lubrication and Maintenance.
Spark plugs that have low mileage may be cleaned
and reused if not otherwise defective. Refer to the
following Spark Plug Condition section of this group.
CONDITION
NORMAL OPERATING
The few deposits present on the spark plug will
probably be light tan or slightly gray in color. This is
evident with most grades of commercial gasoline
(Fig. 19). There will not be evidence of electrode
burning. Gap growth will not average more than ap-
proximately 0.025 mm (.001 in) per 1600 km (1000
miles) of operation. Spark plugs that have normal
wear can usually be cleaned, have the electrodes
filed, have the gap set and then be installed.Some fuel refiners in several areas of the United
States have introduced a manganese additive (MMT)
for unleaded fuel. During combustion, fuel with MMT
causes the entire tip of the spark plug to be coated
with a rust colored deposit. This rust color can be
misdiagnosed as being caused by coolant in the com-
bustion chamber. Spark plug performance is not af-
fected by MMT deposits.
COLD FOULING/CARBON FOULING
Cold fouling is sometimes referred to as carbon
fouling. The deposits that cause cold fouling are ba-
sically carbon (Fig. 19). A dry, black deposit on one or
two plugs in a set may be caused by sticking valves
or defective spark plug cables. Cold (carbon) fouling
of the entire set of spark plugs may be caused by a
clogged air cleaner element or repeated short operat-
ing times (short trips).
WET FOULING OR GAS FOULING
A spark plug coated with excessive wet fuel or oil is
wet fouled. In older engines, worn piston rings, leak-
ing valve guide seals or excessive cylinder wear can
cause wet fouling. In new or recently overhauled en-
gines, wet fouling may occur before break-in (normal
oil control) is achieved. This condition can usually be
resolved by cleaning and reinstalling the fouled
plugs.
OIL OR ASH ENCRUSTED
If one or more spark plugs are oil or oil ash en-
crusted (Fig. 20), evaluate engine condition for the
cause of oil entry into that particular combustion
chamber.
ELECTRODE GAP BRIDGING
Electrode gap bridging may be traced to loose de-
posits in the combustion chamber. These deposits ac-
cumulate on the spark plugs during continuous stop-
and-go driving. When the engine is suddenly
Fig. 18 PCM LocationÐXJ ModelsFig. 19 Normal Operation and Cold (Carbon) Fouling
8D - 12 IGNITION SYSTEMSJ

subjected to a high torque load, deposits partially liq-
uefy and bridge the gap between electrodes (Fig. 21).
This short circuits the electrodes. Spark plugs with
electrode gap bridging can be cleaned using standard
procedures.
SCAVENGER DEPOSITS
Fuel scavenger deposits may be either white or yel-
low (Fig. 22). They may appear to be harmful, but
this is a normal condition caused by chemical addi-
tives in certain fuels. These additives are designed to
change the chemical nature of deposits and decrease
spark plug misfire tendencies. Notice that accumula-
tion on the ground electrode and shell area may be
heavy, but the deposits are easily removed. Sparkplugs with scavenger deposits can be considered nor-
mal in condition and can be cleaned using standard
procedures.
CHIPPED ELECTRODE INSULATOR
A chipped electrode insulator usually results from
bending the center electrode while adjusting the
spark plug electrode gap. Under certain conditions,
severe detonation can also separate the insulator
from the center electrode (Fig. 23). Spark plugs with
this condition must be replaced.
PREIGNITION DAMAGE
Preignition damage is usually caused by excessive
combustion chamber temperature. The center elec-
trode dissolves first and the ground electrode dis-
solves somewhat latter (Fig. 24). Insulators appear
relatively deposit free. Determine if the spark plug
has the correct heat range rating for the engine. De-
termine if ignition timing is over advanced, or if
other operating conditions are causing engine over-
heating. (The heat range rating refers to the operat-
ing temperature of a particular type spark plug.
Spark plugs are designed to operate within specific
Fig. 20 Oil or Ash Encrusted
Fig. 21 Electrode Gap Bridging
Fig. 22 Scavenger Deposits
Fig. 23 Chipped Electrode Insulator
JIGNITION SYSTEMS 8D - 13