2002 JEEP LIBERTY spark plugs

the pan, it will drain first because it is heavier than
oil. An alternative method is to operate engine for a
short period to churn the oil. After this is done,
remove engine dipstick and inspect for water glob-
ules. Also inspect transmission dipstick for water
globules and transmission fluid cooler for leakage.
WARNING: WITH RADIATOR PRESSURE TESTER
TOOL INSTALLED ON RADIATOR, DO NOT ALLOW
PRESSURE TO EXCEED 124 KPA (18 PSI). PRES-
SURE WILL BUILD UP QUICKLY IF A COMBUSTION
LEAK IS PRESENT. TO RELEASE PRESSURE,
ROCK TESTER FROM SIDE TO SIDE. WHEN
REMOVING TESTER, DO NOT TURN TESTER MORE
THAN 1/2 TURN IF SYSTEM IS UNDER PRESSURE.
Operate engine without pressure cap on radiator
until thermostat opens. Attach a Pressure Tester to
filler neck. If pressure builds up quickly it indicates a
combustion leak exists. This is usually the result of a
cylinder head gasket leak or crack in engine. Repair
as necessary.
If there is not an immediate pressure increase,
pump the Pressure Tester. Do this until indicated
pressure is within system range of 110 kPa (16 psi).
Fluctuation of gauge pointer indicates compression or
combustion leakage into cooling system.
Because the vehicle is equipped with a catalytic
converter,do notremove spark plug cables or short
out cylinders to isolate compression leak.
If the needle on dial of pressure tester does not
fluctuate, race engine a few times to check for an
abnormal amount of coolant or steam. This would be
emitting from exhaust pipe. Coolant or steam from
exhaust pipe may indicate a faulty cylinder head gas-
ket, cracked engine cylinder block or cylinder head.A convenient check for exhaust gas leakage into
cooling system is provided by a commercially avail-
able Block Leak Check tool. Follow manufacturers
instructions when using this product.
COMBUSTION LEAKAGE TEST - WITHOUT
PRESSURE TESTER
DO NOT WASTE reusable coolant. If solution is
clean, drain coolant into a clean container for reuse.
WARNING: DO NOT REMOVE CYLINDER BLOCK
DRAIN PLUGS OR LOOSEN RADIATOR DRAIN-
COCK WITH SYSTEM HOT AND UNDER PRESSURE.
SERIOUS BURNS FROM COOLANT CAN OCCUR.
Drain sufficient coolant to allow thermostat
removal. (Refer to 7 - COOLING/ENGINE/ENGINE
COOLANT THERMOSTAT - REMOVAL). Remove
accessory drive belt (Refer to 7 - COOLING/ACCES-
SORY DRIVE/DRIVE BELTS - REMOVAL).
Add coolant to radiator to bring level to within 6.3
mm (1/4 in) of top of thermostat housing.
CAUTION: Avoid overheating. Do not operate
engine for an excessive period of time. Open drain-
cock immediately after test to eliminate boil over.
Start engine and accelerate rapidly three times, to
approximately 3000 rpm while observing coolant. If
internal engine combustion gases are leaking into
cooling system, bubbles will appear in coolant. If bub-
bles do not appear, internal combustion gas leakage
is not present.
KJCOOLING 7 - 5
COOLING (Continued)

WARNING: WITH RADIATOR PRESSURE TESTER
TOOL INSTALLED ON RADIATOR, DO NOT ALLOW
PRESSURE TO EXCEED 124 KPA (18 PSI). PRES-
SURE WILL BUILD UP QUICKLY IF A COMBUSTION
LEAK IS PRESENT. TO RELEASE PRESSURE,
ROCK TESTER FROM SIDE TO SIDE. WHEN
REMOVING TESTER, DO NOT TURN TESTER MORE
THAN 1/2 TURN IF SYSTEM IS UNDER PRESSURE.
Operate engine without pressure cap on radiator
until thermostat opens. Attach a Pressure Tester to
filler neck. If pressure builds up quickly it indicates a
combustion leak exists. This is usually the result of a
cylinder head gasket leak or crack in engine. Repair
as necessary.
If there is not an immediate pressure increase,
pump the Pressure Tester. Do this until indicated
pressure is within system range of 110 kPa (16 psi).
Fluctuation of gauge pointer indicates compression or
combustion leakage into cooling system.
Because the vehicle is equipped with a catalytic
converter,do notremove spark plug cables or short
out cylinders to isolate compression leak.
If the needle on dial of pressure tester does not
fluctuate, race engine a few times to check for an
abnormal amount of coolant or steam. This would be
emitting from exhaust pipe. Coolant or steam from
exhaust pipe may indicate a faulty cylinder head gas-
ket, cracked engine cylinder block or cylinder head.
A convenient check for exhaust gas leakage into
cooling system is provided by a commercially avail-able Block Leak Check tool. Follow manufacturers
instructions when using this product.
COMBUSTION LEAKAGE TEST - WITHOUT
PRESSURE TESTER
DO NOT WASTE reusable coolant. If solution is
clean, drain coolant into a clean container for reuse.
WARNING: DO NOT REMOVE CYLINDER BLOCK
DRAIN PLUGS OR LOOSEN RADIATOR DRAIN-
COCK WITH SYSTEM HOT AND UNDER PRESSURE.
SERIOUS BURNS FROM COOLANT CAN OCCUR.
Drain sufficient coolant to allow thermostat
removal. (Refer to 7 - COOLING/ENGINE/ENGINE
COOLANT THERMOSTAT - REMOVAL). Remove
accessory drive belt (Refer to 7 - COOLING/ACCES-
SORY DRIVE/DRIVE BELTS - REMOVAL).
Add coolant to radiator to bring level to within 6.3
mm (1/4 in) of top of thermostat housing.
CAUTION: Avoid overheating. Do not operate
engine for an excessive period of time. Open drain-
cock immediately after test to eliminate boil over.
Start engine and accelerate rapidly three times, to
approximately 3000 rpm while observing coolant. If
internal engine combustion gases are leaking into
cooling system, bubbles will appear in coolant. If bub-
bles do not appear, internal combustion gas leakage
is not present.
7s - 4 COOLING - 2.4LKJ
COOLING - 2.4L (Continued)

ness routing and retention, connector pin-out infor-
mation and location views for the various wire
harness connectors, splices and grounds.
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Remove the instrument panel center trim
panel.
(3) Remove the radio mounting screws (Fig. 7).
(4) Disconnect the antenna cable by pulling the
locking antenna connector away from the radio (Fig.
8).
(5) Disconnect the electrical harness connector(s).
(6) Remove radio from instrument panel.
INSTALLATION
(1) Connect the wire harness connector(s).
(2) Connect the antenna cable.
(3) Install the radio to the instrument panel.
(4) Install the radio mounting screws.
(5) Install the instrument panel center trim panel.
(6) Connect the battery negative cable.
RADIO NOISE SUPPRESSION
GROUND STRAP
DESCRIPTION
Radio noise suppression devices are factory-in-
stalled standard equipment on this vehicle. Radio
Frequency Interference (RFI) and ElectroMagnetic
Interference (EMI) can be produced by any on-board
or external source of electromagnetic energy. These
electromagnetic energy sources can radiate electro-
magnetic signals through the air, or conduct them
through the vehicle electrical system.
When the audio system converts RFI or EMI to an
audible acoustic wave form, it is referred to as radio
noise. This undesirable radio noise is generally man-
ifested in the form of ªbuzzing,º ªhissing,º ªpopping,º
ªclicking,º ªcrackling,º and/or ªwhirringº sounds. In
most cases, RFI and EMI radio noise can be sup-
pressed using a combination of vehicle and compo-
nent grounding, filtering and shielding techniques.
This vehicle is equipped with factory-installed radio
noise suppression devices that were designed to min-
imize exposure to typical sources of RFI and EMI;
thereby, minimizing radio noise complaints.
Factory-installed radio noise suppression is accom-
plished primarily through circuitry or devices that
are integral to the factory-installed radios, audio
power amplifiers and other on-board electrical com-
ponents such as generators, wiper motors, blower
motors, and fuel pumps that have been found to be
potential sources of RFI or EMI. External radio noise
suppression devices that are used on this vehicle to
control RFI or EMI, and can be serviced, include the
following:
²Engine-to-body ground strap- This length of
braided ground strap has an eyelet terminal connec-
tor crimped to each end. One end is secured to the
engine cylinder head(s). The other is secured to the
plenum.
²Resistor-type spark plugs- This type of spark
plug has an internal resistor connected in series
between the spark plug terminal and the center elec-
trode to help reduce the production of electromag-
netic radiation that can result in radio noise.
Fig. 7 RADIO
Fig. 8 ANTENNA TO RADIO
1 - RADIO
2 - LOCKING ANTENNA CONNECTOR
3 - INSTRUMENT PANEL ANTENNA CABLE
KJAUDIO 8A - 9
RADIO (Continued)

IGNITION CONTROL
TABLE OF CONTENTS
page page
IGNITION CONTROL
DESCRIPTION..........................1
OPERATION............................1
SPECIFICATIONS
SPECIFICATIONS - IGNITION TIMING.......2
ENGINE FIRING ORDER - 2.4L 4-CYLINDER . 2
ENGINE FIRING ORDER - 3.7L V-6.........2
IGNITION COIL RESISTANCE - 2.4L........2
IGNITION COIL RESISTANCE - 3.7L V-6.....3
SPARK PLUGS........................3
SPARK PLUG CABLE RESISTANCE - 2.4L . . . 3
TORQUE - IGNITION SYSTEM............3
AUTO SHUT DOWN RELAY
DESCRIPTION - PCM OUTPUT.............4
OPERATION
OPERATION - ASD SENSE - PCM INPUT....4
OPERATION - PCM OUTPUT.............4
DIAGNOSIS AND TESTING - ASD AND FUEL
PUMP RELAYS........................4
REMOVAL.............................5
INSTALLATION..........................5
CAMSHAFT POSITION SENSOR
DESCRIPTION
DESCRIPTION - 2.4L....................5
DESCRIPTION-3.7L.....................6
OPERATION
OPERATION - 2.4L.....................6OPERATION - 3.7L.....................6
REMOVAL.............................7
INSTALLATION..........................8
IGNITION COIL
DESCRIPTION..........................9
OPERATION............................9
REMOVAL.............................10
INSTALLATION.........................10
KNOCK SENSOR
DESCRIPTION.........................11
OPERATION...........................11
REMOVAL.............................12
INSTALLATION.........................12
SPARK PLUG
DESCRIPTION.........................12
OPERATION...........................12
DIAGNOSIS AND TESTING - SPARK PLUG
CONDITIONS.........................13
REMOVAL.............................15
CLEANING SPARK PLUGS................15
INSTALLATION.........................15
IGNITION COIL CAPACITOR
DESCRIPTION.........................16
OPERATION...........................16
REMOVAL.............................16
INSTALLATION.........................16
IGNITION CONTROL
DESCRIPTION
The ignition system consists of:
²Spark Plugs
²Ignition Coil(s)
²Powertrain Control Module (PCM)
²Crankshaft Position Sensor
²2 Knock Sensors (3.7L only)
²Camshaft Position Sensor
²The MAP, TPS, IAC and ECT also have an effect
on the control of the ignition system.
OPERATION
2.4L
A common ignition coil divided into 2 halves is
used. Secondary, high-tension spark plug cables are
also used. One half of the coil fires two spark plugs
simultaneously (one plug is the cylinder under com-pression, and the other plug is the cylinder on the
exhaust stroke). Coil half number one fires cylinders
1 and 4. Coil half number two fires cylinders 2 and 3.
The PCM determines which of the coils to charge and
fire at the correct time.
The Auto Shutdown (ASD) relay provides battery
voltage to the ignition coil. The PCM provides a
ground contact (circuit) for energizing the coil. When
the PCM breaks the contact, the energy in the coil
primary transfers to the secondary causing a spark.
The PCM will de-energize the ASD relay if it does
not receive inputs from either the crankshaft or cam-
shaft position sensors.
A distributor is not used with the 2.4L engine.
3.7L
The 3.7L V6 engine uses a separate ignition coil for
each cylinder. The one-piece coil bolts directly to the
cylinder head. Rubber boots seal the secondary ter-
minal ends of the coils to the top of all 6 spark plugs.
A separate electrical connector is used for each coil.
KJIGNITION CONTROL 8I - 1

IGNITION COIL RESISTANCE - 3.7L V-6
PRIMARY RESISTANCE
21-27ÉC (70-80ÉF)SECONDARY
RESISTANCE 21-27ÉC
(70-80ÉF)
0.6 - 0.9 Ohms 6,000 - 9,000 Ohms
SPARK PLUGS
ENGINE PLUG TYPE ELECTRODE GAP
2.4L RE14MCC5 (Champion #) 1.24 to 1.37 mm (0.048 to 0.053 in.)
3.7L V-6 2FR6F - 11G (NGK #) 1.1 mm (0.042 in.)
SPARK PLUG CABLE RESISTANCE - 2.4L
MINIMUM MAXIMUM
250 Ohms Per Inch 1000 Ohms Per Inch
3000 Ohms Per Foot 12,000 Ohms Per Foot
TORQUE - IGNITION SYSTEM
DESCRIPTION N-m Ft. Lbs. In. Lbs.
Camshaft Position Sensor-2.4L 23 21 205
Camshaft Position Sensor±3.7L 12 - 106
Crankshaft Position Sensor Bolt-2.4L 12 - 106
Crankshaft Position Sensor Nut/Bolt-3.7L 23 21 205
* Knock Sensor Bolt - 3.7L * 20 * 15
Ignition Coil Mounting Bolts - 2.4L 11 - 105
Ignition Coil Mounting Nuts - 3.7L 8 - 70
Ignition Coil Capacitor Nuts- 3.7L 8 - 70
** Spark Plugs - 2.4L ** 15 ** 11 -
Spark Plugs - 3.7L 27 20 -
* Do not apply any sealant, thread-locker or adhesive to
bolts. Poor sensor performance may result.
** Torque critical tapered design. Do not exceed 15 ft. lbs.
KJIGNITION CONTROL 8I - 3
IGNITION CONTROL (Continued)

3.7L
The Camshaft Position Sensor (CMP) on the 3.7L
V-6 engine is bolted to the front/top of the right cyl-
inder head.
(1) Clean out machined hole in cylinder head.
(2) Apply a small amount of engine oil to sensor
o-ring.
(3) Install sensor into cylinder head with a slight
rocking and twisting action.
CAUTION: Before tightening sensor mounting bolt,
be sure sensor is completely flush to cylinder head.
If sensor is not flush, damage to sensor mounting
tang may result.
(4) Install mounting bolt and tighten. Refer to
torque specifications.
(5) Connect electrical connector to sensor.
IGNITION COIL
DESCRIPTION
2.4L
The coil assembly consists of 2 different coils
molded together. The assembly is mounted to the top
of the engine (Fig. 14).
3.7L
The 3.7L V-6 engine uses 6 dedicated, and individ-
ually fired coil for each spark plug (Fig. 15). Each
coil is mounted directly into the cylinder head and
onto the top of each spark plug (Fig. 16).
OPERATION
2.4L
The coil fires two spark plugs simultaneously. One
plug is under compression, the other plug fires on the
exhaust stroke (lost spark). Coil number one fires
Fig. 14 IGNITION COIL - 2.4L
1 - IGNITION COIL
2 - MOUNTING BOLTS (4)
Fig. 15 IGNITION COIL - 3.7L
1 - O-RING
2 - IGNITION COIL
3 - ELECTRICAL CONNECTOR
Fig. 16 IGNITION COIL LOCATION - 3.7L
1 - IGNITION COIL
2 - COIL MOUNTING NUT
KJIGNITION CONTROL 8I - 9
CAMSHAFT POSITION SENSOR (Continued)

NOTE: Over or under tightening the sensor mount-
ing bolts will affect knock sensor performance, pos-
sibly causing improper spark control. Always use
the specified torque when installing the knock sen-
sors.
REMOVAL
The 2 knock sensors are bolted into the cylinder
block under the intake manifold (Fig. 20).
NOTE: The left sensor is identified by an identifica-
tion tag (LEFT). It is also identified by a larger bolt
head. The Powertrain Control Module (PCM) must
have and know the correct sensor left/right posi-
tions. Do not mix the sensor locations.
(1) Disconnect knock sensor dual pigtail harness
from engine wiring harness. this connection is made
near rear of left valve cover (Fig. 20).
(2) Remove intake manifold. Refer to Engine sec-
tion.
(3) Remove sensor mounting bolts (Fig. 20). Note
foam strip on bolt threads. This foam is used only to
retain the bolts to sensors for plant assembly. It is
not used as a sealant. Do not apply any adhesive,
sealant or thread locking compound to these bolts.
(4) Remove sensors from engine.
INSTALLATION
NOTE: The left sensor is identified by an identifica-
tion tag (LEFT). It is also identified by a larger bolt
head. The Powertrain Control Module (PCM) must
have and know the correct sensor left/right posi-
tions. Do not mix the sensor locations.
(1) Thoroughly clean knock sensor mounting holes.
(2) Install sensors into cylinder block.
NOTE: Over or under tightening the sensor mount-
ing bolts will affect knock sensor performance, pos-
sibly causing improper spark control. Always use
the specified torque when installing the knock sen-
sors. The torque for the knock senor bolt is rela-
tively light for an 8mm bolt.
NOTE: Note foam strip on bolt threads. This foam is
used only to retain the bolts to sensors for plant
assembly. It is not used as a sealant. Do not apply
any adhesive, sealant or thread locking compound
to these bolts.
(3) Install and tighten mounting bolts. Refer to
torque specification.
(4) Install intake manifold. Refer to Engine sec-
tion.
(5) Connect knock sensor wiring harness to engine
harness at rear of intake manifold.
SPARK PLUG
DESCRIPTION
Resistor type spark plugs are used.
Spark plug resistance values range from 6,000 to
20,000 ohms (when checked with at least a 1000 volt
spark plug tester).Do not use an ohmmeter to
check the resistance values of the spark plugs.
Inaccurate readings will result.
OPERATION
To prevent possible pre-ignition and/or mechanical
engine damage, the correct type/heat range/number
spark plug must be used.
Always use the recommended torque when tighten-
ing spark plugs. This is especially true when plugs
are equipped with tapered seats. Incorrect torque can
distort the spark plug and change plug gap. It can
also pull the plug threads and do possible damage to
both the spark plug and the cylinder head.
Remove the spark plugs and examine them for
burned electrodes and fouled, cracked or broken por-
celain insulators. Keep plugs arranged in the order
in which they were removed from the engine. A sin-
Fig. 20 KNOCK SENSOR LOCATION
1 - KNOCK SENSORS (2)
2 - MOUNTING BOLTS
8I - 12 IGNITION CONTROLKJ
KNOCK SENSOR (Continued)

gle plug displaying an abnormal condition indicates
that a problem exists in the corresponding cylinder.
Replace spark plugs at the intervals recommended in
the Lubrication and Maintenance section.
Spark plugs that have low mileage may be cleaned
and reused if not otherwise defective, carbon or oil
fouled. Also refer to Spark Plug Conditions.
CAUTION: Never use a motorized wire wheel brush
to clean the spark plugs. Metallic deposits will
remain on the spark plug insulator and will cause
plug misfire.
DIAGNOSIS AND TESTING - SPARK PLUG
CONDITIONS
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. 21). There will not be evidence of electrode
burning. Gap growth will not average more than
approximately 0.025 mm (.001 in) per 3200 km (2000
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 may be
affected by MMT deposits.
COLD FOULING/CARBON FOULING
Cold fouling is sometimes referred to as carbon
fouling. The deposits that cause cold fouling are basi-
cally carbon (Fig. 21). 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,
leaking valve guide seals or excessive cylinder wear
can cause wet fouling. In new or recently overhauled
engines, wet fouling may occur before break-in (nor-
mal oil control) is achieved. This condition can usu-
ally be resolved by cleaning and reinstalling the
fouled plugs.
OIL OR ASH ENCRUSTED
If one or more spark plugs are oil or oil ash
encrusted (Fig. 22), 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
deposits in the combustion chamber. These deposits
accumulate on the spark plugs during continuous
stop-and-go driving. When the engine is suddenly
Fig. 21 Normal Operation and Cold (Carbon) Fouling
1 - NORMAL
2 - DRY BLACK DEPOSITS
3 - COLD (CARBON) FOULING
Fig. 22 Oil or Ash Encrusted
KJIGNITION CONTROL 8I - 13
SPARK PLUG (Continued)