Jeep Grand Cherokee WK. Manual - part 402

Short term memory is allowed to retard timing up to a preset amount under all operating conditions (as long as rpm
is above the minimum rpm) except at Wide Open Throttle (WOT). The PCM, using short term memory, can respond
quickly to retard timing when engine knock is detected. Short term memory is lost any time the ignition key is turned
off.

NOTE: Over or under tightening the sensor mounting bolts will affect knock sensor performance, possibly
causing improper spark control. Always use the specified torque when installing the knock sensors.

REMOVAL

3.7L V-6

The 2 knock sensors are bolted into the cylinder block
under the intake manifold (1) and (2).

NOTE: The left sensor is identified by an identifi-
cation 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
positions. Do not mix the sensor locations.

1. Disconnect knock sensor dual pigtail harness from

engine wiring harness. This connection is made
near rear of engine.

2. Remove intake manifold. Refer to Engine section.

3. Remove sensor mounting bolts (2). 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.

4.7L V-8

The two knock sensors (1) are bolted into the cylinder
block under the intake manifold (3).

1. Disconnect knock sensor dual pigtail harness from

engine wiring harness. This connection is made
near rear of engine.

2. Remove intake manifold. Refer to Engine section.

3. Remove sensor mounting bolts (2). 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.

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IGNITION SYSTEM - SERVICE INFORMATION

5.7L V8

Two sensors (1) are used. Each sensor is bolted into
the outside of cylinder block below the exhaust mani-
fold (3).

1. Raise vehicle.

2. Disconnect knock sensor electrical connector (5).

3. Remove sensor mounting bolt (2). 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 sensor from engine.

INSTALLATION

3.7L V-6 / 4.7L V-8

NOTE: The left sensor is identified by an identification 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 positions. Do not
mix the sensor locations.

1. Thoroughly clean knock sensor mounting holes.

2. Install sensors into cylinder block.

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 section.

5. Connect knock sensor wiring harness to engine harness at rear of intake manifold.

5.7L V-8

1. Thoroughly clean knock sensor mounting hole.

2. Install sensor into cylinder block.

IGNITION SYSTEM - SERVICE INFORMATION

8I - 29

3. Install and tighten mounting bolt. Refer to torque specification.

4. Install electrical connector to sensor.

SPARK PLUG

DESCRIPTION

Resistor type spark plugs are used on all engines.

Sixteen spark plugs (2 per cylinder) are used with 5.7L V-8 engines.

REMOVAL

3.7L V-6

Each individual spark plug is located under each ignition coil. Each individual ignition coil must be removed to gain
access to each spark plug. Refer to Ignition Coil Removal/Installation.

1. Remove necessary air filter tubing at throttle body.

2. Prior to removing ignition coil, spray compressed air around coil base at cylinder head.

3. Prior to removing spark plug, spray compressed air into cylinder head opening. This will help prevent foreign

material from entering combustion chamber.

4. Remove spark plug from cylinder head using a quality socket with a rubber or foam insert. Also check condition

of ignition coil o-ring and replace as necessary.

5. Inspect spark plug condition.

4.7L V-8

Each individual spark plug is located under each ignition coil. Each individual ignition coil must be removed to gain
access to each spark plug. Refer to Ignition Coil Removal/Installation.

1. Remove necessary air filter tubing at throttle body.

2. Prior to removing ignition coil, spray compressed air around coil base at cylinder head.

3. Prior to removing spark plug, spray compressed air into cylinder head opening. This will help prevent foreign

material from entering combustion chamber.

4. Remove spark plug from cylinder head using a quality socket with a rubber or foam insert. Also check condition

of ignition coil o-ring and replace as necessary.

5. Inspect spark plug condition..

5.7L V-8

Eight of the 16 spark plugs are located under an ignition coil; the other 8 are not. If spark plug being removed is
under coil, coil must be removed to gain access to spark plug. Refer to Ignition Coil Removal/Installation and
observe all CAUTIONS and WARNINGS.

Before removing or disconnecting any spark plug cables, note their original position. Remove cables one-at-a-time.
To prevent ignition crossfire, spark plug cables MUST be placed in cable tray (routing loom) into their original posi-
tion. Refer to Spark Plug Cable Removal for a graphic.

Before installing spark plug cables to either the spark plugs or coils, apply dielectric grease to inside of boots.

1. Remove necessary air filter tubing at throttle body.

2. Prior to removing ignition coil (if coil removal is necessary), spray compressed air around coil base at cylinder

head cover.

3. Prior to removing spark plug, spray compressed air into cylinder head opening. This will help prevent foreign

material from entering combustion chamber.

4. Remove spark plug from cylinder head using a quality socket with a rubber or foam insert.

5. Inspect spark plug condition.

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IGNITION SYSTEM - SERVICE INFORMATION

CLEANING

CLEANING AND ADJUSTMENT

The plugs may be cleaned using commercially avail-
able spark plug cleaning equipment. After cleaning, file
center electrode flat with a small point file or jewelers
file before adjusting gap.

CAUTION: Never use a motorized wire wheel
brush to clean spark plugs. Metallic deposits will
remain on spark plug insulator and will cause plug
misfire.

Adjust spark plug gap with a gap gauging tool (1).

INSTALLATION

3.7L V-6

Special care should be taken when installing spark plugs into the cylinder head spark plug wells. Be sure the plugs
do not drop into the plug wells as electrodes can be damaged.

Always tighten spark plugs to the specified torque. Over tightening can cause distortion resulting in a change in the
spark plug gap or a cracked porcelain insulator.

1. Start the spark plug into the cylinder head by hand to avoid cross threading.

2. Tighten spark plugs. Refer to torque specifications.

3. Before installing ignition coil(s), check condition of coil o-ring and replace as necessary. To aid in coil installation,

apply silicone to coil o-ring.

4. Install ignition coil(s). Refer to Ignition Coil Removal/Installation.

4.7L V-8

CAUTION: The 4.7L V–8 engine is equipped with copper core ground electrode spark plugs. They must be
replaced with the same type/number spark plug as the original. If another spark plug is substituted, pre-
ignition will result.

Special care should be taken when installing spark plugs into the cylinder head spark plug wells. Be sure the plugs
do not drop into the plug wells as electrodes can be damaged.

Always tighten spark plugs to the specified torque. Over tightening can cause distortion resulting in a change in the
spark plug gap or a cracked porcelain insulator.

1. Start the spark plug into the cylinder head by hand to avoid cross threading.

2. Tighten spark plugs. Refer to torque specifications.

3. Before installing ignition coil(s), check condition of coil o-ring and replace as necessary. To aid in coil installation,

apply silicone to coil o-ring.

4. Install ignition coil(s). Refer to Ignition Coil Removal/Installation.

IGNITION SYSTEM - SERVICE INFORMATION

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