Camshaft Position Sensor - 2.4L Operation

TJ IGNITION CONTROL 8I - 1

IGNITION CONTROL

TABLE OF CONTENTS

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IGNITION CONTROL OPERATION - 4.0L ...... 8 DESCRIPTION ...... 1 REMOVAL - 4.0L ...... 8 OPERATION ...... 1 INSTALLATION - 4.0L ...... 10 SPECIFICATIONS COIL RAIL - 4.0L SPECIFICATIONS - IGNITION TIMING ...... 2 DESCRIPTION - 4.0L ...... 10 ENGINE FIRING ORDER - 2.4L 4-CYLINDER . 2 OPERATION - 4.0L ...... 11 ENGINE FIRING ORDER - 4.0L 6-CYLINDER REMOVAL - 4.0L ...... 11 ENGINE ...... 2 INSTALLATION - 4.0L ...... 12 IGNITION COIL RESISTANCE - 2.4L ...... 2 IGNITION COIL - 2.4L IGNITION COIL RESISTANCE - 4.0L ENGINE . 3 DESCRIPTION - 2.4L ...... 13 SPARK PLUGS ...... 3 OPERATION - 2.4L ...... 13 SPECIFICATIONS - SPARK PLUG CABLE REMOVAL - 2.4L ...... 13 RESISTANCE ...... 3 INSTALLATION - 2.4L ...... 13 SPECIFICATIONS - TORQUE - IGNITION SPARK PLUG SYSTEM ...... 3 DESCRIPTION ...... 13 AUTO SHUT DOWN RELAY OPERATION ...... 13 DESCRIPTION - PCM OUTPUT ...... 4 DIAGNOSIS AND TESTING - SPARK PLUG OPERATION CONDITIONS ...... 14 OPERATION - ASD SENSE - PCM INPUT ....4 REMOVAL ...... 16 OPERATION - PCM OUTPUT ...... 4 CLEANING DIAGNOSIS AND TESTING - ASD AND FUEL CLEANING SPARK PLUGS ...... 16 PUMP RELAYS ...... 4 INSTALLATION ...... 17 REMOVAL ...... 5 SPARK PLUG CABLE INSTALLATION ...... 5 DESCRIPTION ...... 17 CAMSHAFT POSITION SENSOR - 2.4L OPERATION ...... 17 DESCRIPTION - 2.4L ...... 5 DIAGNOSIS AND TESTING ...... 17 OPERATION - 2.4L ...... 5 REMOVAL - 2.4L ...... 18 REMOVAL - 2.4L ...... 6 INSTALLATION ...... 18 INSTALLATION - 2.4L ...... 6 CAMSHAFT POSITION SENSOR - 4.0L DESCRIPTION - 4.0L ...... 7

IGNITION CONTROL OPERATION DESCRIPTION 2.4L The ignition systems used on both the 2.4L 4–cyl- A common ignition coil divided into 2 halves is inder and 4.0L 6–cylinder engines are a distributor- used. Secondary, high-tension spark plug cables are less type. also used. One half of the coil fires two spark plugs The ignition system consists of: simultaneously (one plug is the cylinder under com- • Spark Plugs pression, and the other plug is the cylinder on the • Spark Plug Cables (secondary wires) exhaust stroke). Coil half number one fires cylinders • Ignition Coil(s) 1 and 4. Coil half number two fires cylinders 2 and 3. • Powertrain Control Module (PCM) The PCM determines which of the coils to charge and • Crankshaft Position Sensor fire at the correct time. • Camshaft Position Sensor The Auto Shutdown (ASD) relay provides battery • The MAP, TPS, IAC and ECT also have an effect voltage to the ignition coil. The PCM provides a on the control of the ignition system. ground contact (circuit) for energizing the coil. When the PCM breaks the contact, the energy in the coil 8I - 2 IGNITION CONTROL TJ IGNITION CONTROL (Continued) primary transfers to the secondary causing a spark. ENGINE FIRING ORDER - 4.0L 6-CYLINDER The PCM will de-energize the ASD relay if it does ENGINE not receive inputs from either the crankshaft or camshaft position sensors. A distributor is not used with the 2.4L engine. 4.0L The 4.0L 6-cylinder engine uses a one-piece coil rail containing three independent coils. Although cylinder firing order is the same as 4.0L engines of previous years, spark plug firing is not. The 3 coils dual- fire the spark plugs on cylinders 1-6, 2-5 and/or 3-4. When one cylinder is being fired (on compression stroke), the spark to the opposite cylinder is being wasted (on exhaust stroke). The one-piece coil bolts directly to the cylinder head. Rubber boots seal the secondary terminal ends of the coils to the top of all 6 spark plugs. One electrical connector (located at the rear end of the coil rail) is used for all three coils. Because of coil design, spark plug cables (secondary cables) are not used. A distributor is not used with the 4.0L engine. The ignition system is controlled by the Powertrain Control Module (PCM).

FIRING ORDER - 4.0L SPECIFICATIONS SPECIFICATIONS - IGNITION TIMING Ignition timing is not adjustable on any engine. ENGINE FIRING ORDER - 2.4L 4-CYLINDER 1 - 3-4-2

IGNITION COIL RESISTANCE - 2.4L

Primary Resistance at Secondary Resistance at Engine Coil Manufacture 21°C-27°C (70°F-80°F) 21°C-27°C (70°F-80°F) 2.4L Toyodenso or Diamond 0.51 to 0.61 Ohms 11,500 to 13,500 Ohms TJ IGNITION CONTROL 8I - 3 IGNITION CONTROL (Continued) IGNITION COIL RESISTANCE - 4.0L ENGINE

PRIMARY RESISTANCE 21-27°C (70-80°F) 0.71 - 0.88 Ohms

IGNITION COIL - 2.4L

SPARK PLUGS

ENGINE PLUG TYPE ELECTRODE GAP 2.4L 4-Cylinder RE14MCC5 (Champion #) 1.24 to 1.37 mm (0.048 to 0.053 in.) 4.0L 6-Cylinder ZFR5N (NGK #) 1.00 mm (0.040 in.)

SPECIFICATIONS - SPARK PLUG CABLE RESISTANCE

MINIMUM MAXIMUM 250 Ohms Per Inch 1000 Ohms Per Inch 3000 Ohms Per Foot 12,000 Ohms Per Foot

SPECIFICATIONS - TORQUE - IGNITION SYSTEM

DESCRIPTION N·m Ft. Lbs. In. Lbs. Camshaft Position Sensor Mounting Bolts – 4.0L 2 - 15 Camshaft Position Sensor – 2.4L 12 - 106 Ignition Coil Rail Mounting Bolts – 4.0L 29 - 250 Ignition Coil Mounting Bolts – 2.4L 11 - 105 Oil Pump Drive Hold-down Bolt – 4.0L 23 17 - ** Spark Plugs - 2.4L 4-Cylinder 15 11 - Spark Plugs - 4.0L 6-cylinder 30 22 - ** Torque critical tapered design. Do not exceed 15 ft. lbs. torque. 8I - 4 IGNITION CONTROL TJ

AUTO SHUT DOWN RELAY DESCRIPTION - PCM OUTPUT The 5–pin, 12–volt, Automatic Shutdown (ASD) relay is located in the Power Distribution Center (PDC). Refer to label on PDC cover for relay location.

OPERATION OPERATION - ASD SENSE - PCM INPUT A 12 volt signal at this input indicates to the PCM that the ASD has been activated. The relay is used to connect the oxygen sensor heater element, ignition Fig. 1 ASD and Fuel Pump Relay Terminals—Type 1 coil and fuel injectors to 12 volt + power supply. This input is used only to sense that the ASD relay is energized. If the Powertrain Control Module (PCM) does not see 12 volts at this input when the ASD should be activated, it will set a Diagnostic Trouble Code (DTC). OPERATION - PCM OUTPUT The ASD relay supplies battery voltage (12+ volts) to the fuel injectors and ignition coil(s). With certain emissions packages it also supplies 12–volts to the oxygen sensor heating elements. The ground circuit for the coil within the ASD relay is controlled by the Powertrain Control Module (PCM). The PCM operates the ASD relay by switch- ing its ground circuit on and off. The ASD relay will be shut–down, meaning the Fig. 2 ASD and Fuel Pump Relay Terminals—Type 2 12–volt power supply to the ASD relay will be de-ac- TERMINAL LEGEND tivated by the PCM if: NUMBER IDENTIFICATION • the ignition key is left in the ON position. This is if the engine has not been running for approxi- 30 COMMON FEED 85 COIL GROUND mately 1.8 seconds. 86 COIL BATTERY • there is a crankshaft position sensor signal to 87 NORMALLY OPEN the PCM that is lower than pre-determined values. 87A NORMALLY CLOSED DIAGNOSIS AND TESTING - ASD AND FUEL voltage is not supplied to the rest of the circuit. Ter- minal 87A is the center terminal on the relay. PUMP RELAYS • When the PCM energizes the ASD and fuel The following description of operation and pump relays, terminal 87 connects to terminal 30. tests apply only to the Automatic Shutdown This is the On position. Terminal 87 supplies voltage (ASD) and fuel pump relays. The terminals on the to the rest of the circuit. bottom of each relay are numbered. Two different The following procedure applies to the ASD and types of relays may be used, (Fig. 1) or (Fig. 2). fuel pump relays. • Terminal number 30 is connected to battery volt- (1) Remove relay from connector before testing. age. For both the ASD and fuel pump relays, termi- (2) With the relay removed from the vehicle, use nal 30 is connected to battery voltage at all times. an ohmmeter to check the resistance between termi- • The PCM grounds the coil side of the relay nals 85 and 86. The resistance should be 75 ohms +/- through terminal number 85. 5 ohms. • Terminal number 86 supplies voltage to the coil (3) Connect the ohmmeter between terminals 30 side of the relay. and 87A. The ohmmeter should show continuity • When the PCM de-energizes the ASD and fuel between terminals 30 and 87A. pump relays, terminal number 87A connects to terminal 30. This is the Off position. In the off position, TJ IGNITION CONTROL 8I - 5 AUTO SHUT DOWN RELAY (Continued)

(4) Connect the ohmmeter between terminals 87 (4) Check for pin height (pin height should be the and 30. The ohmmeter should not show continuity at same for all terminals within the PDC connector). this time. Repair if necessary before installing relay. (5) Connect one end of a jumper wire (16 gauge or smaller) to relay terminal 85. Connect the other end INSTALLATION of the jumper wire to the ground side of a 12 volt The ASD relay is located in the Power Distribution power source. Center (PDC) (Fig. 3). Refer to label on PDC cover (6) Connect one end of another jumper wire (16 for relay location. gauge or smaller) to the power side of the 12 volt (1) Install relay to PDC. power source. Do not attach the other end of the (2) Install cover to PDC. jumper wire to the relay at this time.

WARNING: DO NOT ALLOW OHMMETER TO CON- CAMSHAFT POSITION TACT TERMINALS 85 OR 86 DURING THIS TEST. SENSOR - 2.4L DAMAGE TO OHMMETER MAY RESULT.

(7) Attach the other end of the jumper wire to DESCRIPTION - 2.4L relay terminal 86. This activates the relay. The ohm- The Camshaft Position Sensor (CMP) on the 2.4L meter should now show continuity between relay ter- 4–cylinder engine is bolted to the right-front side of minals 87 and 30. The ohmmeter should not show the cylinder head (Fig. 4). continuity between relay terminals 87A and 30. (8) Disconnect jumper wires. (9) Replace the relay if it did not pass the continuity and resistance tests. If the relay passed the tests, it operates properly. Check the remainder of the ASD and fuel pump relay circuits. Refer to 8, Wiring Dia- grams. REMOVAL The ASD relay is located in the Power Distribution Center (PDC) (Fig. 3). Refer to label on PDC cover for relay location.

Fig. 4 CMP LOCATION - 2.4L 1 - CMP SENSOR 2 - ELECTRICAL CONNECTOR 3 - SLOTTED HOLES 4 - MOUNTING BOLTS (2) OPERATION - 2.4L The Camshaft Position Sensor (CMP) sensor contains a hall effect device referred to as a sync signal generator. A rotating target wheel (tonewheel) for the Fig. 3 Power Distribution Center (PDC) CMP is located behind the exhaust valve-camshaft drive gear (Fig. 5). The target wheel is equipped with 1 - BATTERY 2 - POWER DISTRIBUTION CENTER (PDC) a cutout (notch) around 180 degrees of the wheel. The CMP detects this cutout every 180 degrees of (1) Remove PDC cover. camshaft gear rotation. Its signal is used in conjunc- (2) Remove relay from PDC. tion with the Crankshaft Position Sensor (CKP) to (3) Check condition of relay terminals and PDC differentiate between fuel injection and spark events. connector terminals for damage or corrosion. Repair It is also used to synchronize the fuel injectors with if necessary before installing relay. their respective cylinders. 8I - 6 IGNITION CONTROL TJ CAMSHAFT POSITION SENSOR - 2.4L (Continued)

When the leading edge of the target wheel cutout enters the tip of the CMP, the interruption of magnetic field causes the voltage to switch high, resulting in a sync signal of approximately 5 volts. When the trailing edge of the target wheel cutout leaves the tip of the CMP, the change of the magnetic field causes the sync signal voltage to switch low to 0 volts.

Fig. 6 CMP LOCATION - 2.4L 1 - CMP SENSOR 2 - ELECTRICAL CONNECTOR 3 - SLOTTED HOLES 4 - MOUNTING BOLTS (2)

(2) Rotate (bump over) engine until camshaft timing gear and target wheel (tonewheel) are positioned and aligned to face of sensor as shown in (Fig. 8). If Fig. 5 CMP FACE AT TARGET WHEEL-2.4L not positioned as shown in (Fig. 8), damage to 1 - CAMSHAFT DRIVE GEAR both sensor and target wheel will occur when 2 - TARGETWHEEL (TONEWHEEL) attempting to start engine. Face of sensor 3 - FACE OF CMP SENSOR MUST be behind target wheel while adjusting. 4 - CUTOUT (NOTCH) (3) Position sensor to cylinder head and install 2 sensor mounting bolts finger tight. REMOVAL - 2.4L (4) SENSOR AIR GAP: .030” Set air gap between The Camshaft Position Sensor (CMP) on the 2.4L rear of target wheel and face of sensor to .030”. This 4–cylinder engine is bolted to the right-front side of can best be accomplished using an L-shaped, wire- the cylinder head (Fig. 6). Sensor position (depth) is type spark plug gapping gauge (Fig. 9). A piece of adjustable. .030” brass shim stock may also be used. (1) Disconnect electrical connector at CMP sensor. (5) Gently push sensor forward until it contacts (2) Remove 2 sensor mounting bolts. gapping gauge. Do not push hard on sensor. (3) Remove sensor from cylinder head by sliding Tighten 2 sensor mounting bolts. Refer to torque towards rear of engine. specifications.

INSTALLATION - 2.4L CAUTION: After tightening sensor mounting bolts, The Camshaft Position Sensor (CMP) on the 2.4L recheck air gap and adjust as necessary. Retorque 4–cylinder engine is bolted to the right-front side of bolts. the cylinder head. Sensor position (depth) is adjustable. (6) Install upper timing belt cover and 3 bolts. (1) Remove plastic, upper timing belt cover (timing (7) Connect electrical connector to ECT sensor. gear cover) (Fig. 7) by removing 3 bolts. Before (8) Connect electrical connector to CMP sensor. attempting to remove cover, remove electrical connector from Engine Coolant Temperature (ECT) sensor (Fig. 7). This will prevent damage to sensor. TJ IGNITION CONTROL 8I - 7 CAMSHAFT POSITION SENSOR - 2.4L (Continued)

Fig. 7 UPPER TIMING BELT COVER/BOLTS-2.4L Fig. 9 CMP ADJUSTMENT - 2.4L 1 - UPPER TIMING BELT COVER 2 - ELECTRICAL CONNECTOR (ECT) 1 - FACE OF SENSOR 3 - MOUNTING BOLTS (3) 2 - WIRE GAPPING TOOL

Fig. 8 CMP FACE AT TARGET WHEEL-2.4L 1 - CAMSHAFT DRIVE GEAR 2 - TARGETWHEEL (TONEWHEEL) 3 - FACE OF CMP SENSOR 4 - CUTOUT (NOTCH) CAMSHAFT POSITION SENSOR - 4.0L Fig. 10 CMP and Oil Pump Drive Shaft—4.0L Engine 1 - CAMSHAFT POSITION SENSOR DESCRIPTION - 4.0L 2 - MOUNTING BOLTS (2) 3 - PULSE RING The Camshaft Position Sensor (CMP) on the 4.0L 4 - DRIVE GEAR (TO CAMSHAFT) 6–cylinder engine is bolted to the top of the oil pump 5 - OIL PUMP DRIVESHAFT drive shaft assembly (Fig. 10). The sensor and drive 6 - SENSOR BASE (OIL PUMP DRIVESHAFT ASSEMBLY) shaft assembly is located on the right side of the engine near the oil filter (Fig. 11). 8I - 8 IGNITION CONTROL TJ CAMSHAFT POSITION SENSOR - 4.0L (Continued) REMOVAL - 4.0L The Camshaft Position Sensor (CMP) on the 4.0L 6–cylinder engine is bolted to the top of the oil pump drive shaft assembly (Fig. 12). The sensor and drive shaft assembly is located on the right side of the engine near the oil filter (Fig. 13). The rotational position of oil pump drive determines fuel synchronization only. It does not determine ignition timing.

NOTE: Do not attempt to rotate the oil pump drive to modify ignition timing.

Two different procedures are used for removal and installation. The first procedure will detail removal and installation of the sensor only. The second procedure will detail removal and installation of the sensor and oil pump drive shaft assembly. The second procedure is to be used if the engine has been disassembled. An internal oil seal is used in the drive shaft hous- Fig. 11 CMP Location—4.0L Engine ing that prevents engine oil at the bottom of the sensor. The seal is not serviceable. 1 - OIL FILTER 2 - CAMSHAFT POSITION SENSOR 3 - CLAMP BOLT 4 - HOLD-DOWN CLAMP 5 - MOUNTING BOLTS (2) 6 - ELEC. CONNECTOR OPERATION - 4.0L The CMP sensor contains a hall effect device called a sync signal generator to generate a fuel sync signal. This sync signal generator detects a rotating pulse ring (shutter) on the oil pump drive shaft (Fig. 10). The pulse ring rotates 180 degrees through the sync signal generator. Its signal is used in conjunc- tion with the crankshaft position sensor to differentiate between fuel injection and spark events. It is also used to synchronize the fuel injectors with their respective cylinders. When the leading edge of the pulse ring (shutter) enters the sync signal generator, the following occurs: The interruption of magnetic field causes the voltage to switch high resulting in a sync signal of approximately 5 volts. When the trailing edge of the pulse ring (shutter) leaves the sync signal generator, the following occurs: The change of the magnetic field causes the sync signal voltage to switch low to 0 volts.

Fig. 12 CMP and Oil Pump Drive Shaft - 4.0L Engine 1 - CAMSHAFT POSITION SENSOR 2 - MOUNTING BOLTS (2) 3 - PULSE RING 4 - DRIVE GEAR (TO CAMSHAFT) 5 - OIL PUMP DRIVESHAFT 6 - SENSOR BASE (OIL PUMP DRIVESHAFT ASSEMBLY) TJ IGNITION CONTROL 8I - 9 CAMSHAFT POSITION SENSOR - 4.0L (Continued)

Fig. 13 CMP Location - 4.0L Engine Fig. 15 Align Timing Marks - 4.0L Engine 1 - OIL FILTER 1 - CRANKSHAFT VIBRATION DAMPER TIMING MARK 2 - CAMSHAFT POSITION SENSOR 3 - CLAMP BOLT 4 - HOLD-DOWN CLAMP SENSOR ONLY - 4.0L 5 - MOUNTING BOLTS (2) (1) Disconnect electrical connector at CMP sensor 6 - ELEC. CONNECTOR (Fig. 13). (2) Remove 2 sensor mounting bolts (Fig. 12) or (Fig. 13). (3) Remove sensor from oil pump drive. OIL PUMP DRIVE AND SENSOR - 4.0L If the CMP and oil pump drive are to be removed and installed, do not allow engine crankshaft or camshaft to rotate. CMP sensor relationship will be lost. (1) Disconnect electrical connector at CMP sensor (Fig. 13). (2) Remove 2 sensor mounting bolts (Fig. 12) or (Fig. 13). (3) Remove sensor from oil pump drive. (4) Before proceeding to next step, mark and note rotational position of oil pump drive in relationship to engine block. After installation, the CMP sensor should face rear of engine 0°. (5) Remove hold-down bolt and clamp (Fig. 13). (6) While pulling assembly from engine, note direction and position of pulse ring (Fig. 12). After removal, look down into top of oil pump and note direction and position of slot at top of oil pump gear. Fig. 14 CMP Pulse Ring Alignment - 4.0L Engine (7) Remove and discard old oil pump drive-to-en- 1 - PULSE RING (SHUTTER) 2 - TOOTHPICK gine block gasket. 3 - SENSOR BASE (OIL PUMP DRIVESHAFT ASSEMBLY) 8I - 10 IGNITION CONTROL TJ CAMSHAFT POSITION SENSOR - 4.0L (Continued) INSTALLATION - 4.0L (8) Connect electrical connector to CMP sensor. (9) If removed, install spark plug and ignition coil SENSOR ONLY - 4.0L rail. The Camshaft Position Sensor (CMP) on the 4.0L To verify correct rotational position of oil pump 6–cylinder engine is bolted to the top of the oil pump drive, the DRB scan tool must be used. drive shaft assembly (Fig. 12). The sensor and drive shaft assembly is located on the right side of the WARNING: WHEN PERFORMING THE FOLLOWING engine near the oil filter (Fig. 13). TEST, THE ENGINE WILL BE RUNNING. BE CARE- (1) Install sensor to oil pump drive. FUL NOT TO STAND IN LINE WITH THE FAN (2) Install 2 sensor mounting bolts and tighten to BLADES OR FAN BELT. DO NOT WEAR LOOSE 2 N·m (15 in. lbs.) torque. CLOTHING. (3) Connect electrical connector to CMP sensor. (10) Connect DRB scan tool to data link connector. OIL PUMP DRIVE AND SENSOR - 4.0L The data link connector is located in passenger com- partment, below and to left of steering column. (1) Clean oil pump drive mounting hole area of (11) Gain access to SET SYNC screen on DRB. engine block. (12) Follow directions on DRB screen and start (2) Install new oil pump drive-to-engine block gas- engine. Bring to operating temperature (engine must ket. be in “closed loop” mode). (3) Temporarily install a toothpick or similar tool (13) With engine running at idle speed, the words through access hole at side of oil pump drive housing. IN RANGE should appear on screen along with 0°. Align toothpick into mating hole on pulse ring (Fig. This indicates correct position of oil pump drive. 14). (14) If a plus (+) or a minus (-) is displayed next to (4) Install oil pump drive into engine while align- degree number, and/or the degree displayed is not ing into slot on oil pump. Rotate oil pump drive back zero, loosen but do not remove hold-down clamp bolt. to its original position and install hold-down clamp Rotate oil pump drive until IN RANGE appears on and bolt. Finger tighten bolt. Do not do a final tight- screen. Continue to rotate oil pump drive until ening of bolt at this time. achieving as close to 0° as possible. (5) If engine crankshaft or camshaft has been The degree scale on SET SYNC screen of DRB is rotated, such as during engine tear-down, CMP sen- referring to fuel synchronization only. It is not sor relationship must be reestablished. referring to ignition timing. Because of this, do (a) Remove ignition coil rail assembly. Refer to not attempt to adjust ignition timing using this Ignition Coil Removal/Installation. method. Rotating oil pump drive will have no effect (b) Remove cylinder number 1 spark plug. on ignition timing. All ignition timing values are con- (c) Hold a finger over the open spark plug hole. trolled by powertrain control module (PCM). Rotate engine at vibration dampener bolt until (15) Tighten hold-down clamp bolt to 23 N·m (17 compression (pressure) is felt. ft. lbs.) torque. (d) Slowly continue to rotate engine. Do this until timing index mark on vibration damper pul- ley aligns with top dead center (TDC) mark (0 COIL RAIL - 4.0L degree) on timing degree scale (Fig. 15). Always rotate engine in direction of normal rotation. Do DESCRIPTION - 4.0L not rotate engine backward to align timing marks. A one-piece coil rail assembly containing three (e) Install oil pump drive into engine while individual coils is used on the 4.0L 6–cylinder engine aligning into slot on oil pump. If pump drive will (Fig. 16). The coil rail must be replaced as one not drop down flush to engine block, the oil pump assembly. The bottom of the coil is equipped with 6 slot is not aligned. Remove oil pump drive and individual rubber boots (Fig. 16) to seal the 6 spark align slot in oil pump to shaft at bottom of drive. plugs to the coil. Inside each rubber boot is a spring. Install into engine. Rotate oil pump drive back to The spring is used for a mechanical contact between its original position and install hold-down clamp the coil and the top of the spark plug. These rubber and bolt. Finger tighten bolt. Do not do a final boots and springs are a permanent part of the coil tightening of bolt at this time. and are not serviced separately. (f) Remove toothpick from housing. (1) The coil is bolted directly to the cylinder head (6) Install sensor to oil pump drive. After installa- (Fig. 17). One electrical connector (located at rear of tion, the CMP sensor should face rear of engine 0°. coil) is used for all three coils. (7) Install 2 sensor mounting bolts and tighten to 2 N·m (15 in. lbs.) torque. TJ IGNITION CONTROL 8I - 11 COIL RAIL - 4.0L (Continued) OPERATION - 4.0L Although cylinder firing order is the same as 4.0L Jeep engines of previous years, spark plug firing is not. The 3 coils dual-fire the spark plugs on cylinders 1-6, 2-5 and/or 3-4. When one cylinder is being fired (on compression stroke), the spark to the opposite cylinder is being wasted (on exhaust stroke). Battery voltage is supplied to the three ignition coils from the ASD relay. The Powertrain Control Module (PCM) opens and closes the ignition coil ground circuit for ignition coil operation. Base ignition timing is not adjustable. By con- trolling the coil ground circuit, the PCM is able to set the base timing and adjust the ignition timing advance. This is done to meet changing engine operating conditions. The ignition coil is not oil filled. The windings are embedded in an epoxy compound. This provides heat and vibration resistance that allows the ignition coil to be mounted on the engine. Fig. 16 Ignition Coil Assembly—4.0L 6–Cylinder Because of coil design, spark plug cables (second- Engine ary cables) are not used. The cables are integral within the coil rail. 1 - CYL. #6 2 - CYL. #5 3 - CYL. #4 REMOVAL - 4.0L 4 - CYL. #3 5 - CYL. #2 A one-piece coil rail assembly containing three 6 - CYL. #1 individual coils is used on the 4.0L engine (Fig. 18). 7 - COILS (3) The coil rail must be replaced as one assembly. The 8 - MOUNTING BOLTS (4) 9 - BOLT BASES (4) bottom of the coil is equipped with 6 individual rub- 10 - RUBBER BOOTS (6) ber boots (Fig. 18) to seal the 6 spark plugs to the coil. Inside each rubber boot is a spring. The spring is used for an electrical contact between the coil and the top of the spark plug. These rubber boots and springs are a permanent part of the coil and are not serviced separately. (1) Disconnect negative battery cable at battery. (2) The coil is bolted directly to the cylinder head. Remove 4 coil mounting bolts (Fig. 19). (3) Carefully pry up coil assembly from spark plugs. Do this by prying alternately at each end of coil until rubber boots have disengaged from all spark plugs. If boots will not release from spark plugs, use a commercially available spark plug boot removal tool. Twist and loosen a few boots from a few spark plugs to help remove coil. (4) After coil has cleared spark plugs, position coil for access to primary electrical connector. Disconnect Fig. 17 Coil Location—4.0L Engine connector from coil by pushing slide tab outwards to 1 - COIL RAIL right side of vehicle (Fig. 20). After slide tab has been 2 - COIL MOUNTING BOLTS (4) positioned outwards, push in on secondary release 3 - COIL 4 - COIL ELECTRICAL CONNECTION lock (Fig. 20) on side of connector and pull connector from coil. (5) Remove coil from vehicle. 8I - 12 IGNITION CONTROL TJ COIL RAIL - 4.0L (Continued)

Fig. 18 Ignition Coil Assembly—4.0L 6–Cylinder Engine Fig. 20 Ignition Coil Electrical Connector—4.0L 1 - CYL. #6 2 - CYL. #5 6–Cylinder Engine 3 - CYL. #4 1 - REAR OF VALVE COVER 4 - CYL. #3 2 - COIL RAIL 5 - CYL. #2 3 - SLIDE TAB 6 - CYL. #1 4 - RELEASE LOCK 7 - COILS (3) 5 - COIL CONNECTOR 8 - MOUNTING BOLTS (4) 9 - BOLT BASES (4) 10 - RUBBER BOOTS (6) INSTALLATION - 4.0L (1) Connect engine harness connector to coil by snapping into position. Move slide tab towards engine (Fig. 20) for a positive lock. (2) Position ignition coil rubber boots to all spark plugs. Push down on coil assembly until bolt bases have contacted cylinder head (3) Install 4 coil mounting bolts. Loosely tighten 4 bolts just enough to allow bolt bases to contact cylinder head. Do a final tightening of each bolt in steps down to 29 N·m (250 in. lbs.) torque. Do not apply full torque to any bolt first. (4) Connect negative battery cable to battery.

Fig. 19 Ignition Coil Rail Location—4.0L 6–Cylinder Engine 1 - COIL RAIL 2 - COIL MOUNTING BOLTS (4) 3 - COIL 4 - COIL ELECTRICAL CONNECTION TJ IGNITION CONTROL 8I - 13

IGNITION COIL - 2.4L REMOVAL - 2.4L (1) Disconnect electrical connector at rear of coil. DESCRIPTION - 2.4L (2) Remove all secondary cables from coil. The coil assembly consists of 2 different coils (3) Remove 4 coil mounting bolts (Fig. 22). molded together. The assembly is mounted to the top (4) Remove coil from vehicle. of the engine (Fig. 21).

Fig. 22 IGNITION COIL - 2.4L Fig. 21 IGNITION COIL - 2.4L 1 - IGNITION COIL 2 - MOUNTING BOLTS (4) 1 - IGNITION COIL 2 - MOUNTING BOLTS (4) INSTALLATION - 2.4L OPERATION - 2.4L (1) Position coil to engine. The coil fires two spark plugs simultaneously. One (2) Install 4 mounting bolts. Refer to torque speci- plug is under compression, the other plug fires on the fications. exhaust stroke (lost spark). Coil number one fires (3) Install secondary cables. cylinders 1 and 4, and coil number two fires cylinders (4) Install electrical connector at rear of coil. 2 and 3. (5) Install air cleaner tube and housing. The Auto Shutdown (ASD) relay provides battery voltage to the ignition coil. The PCM provides a ground contact (circuit) for energizing the coil(s). The SPARK PLUG PCM will de-energize the ASD relay if it does not receive the crankshaft position sensor and camshaft DESCRIPTION position sensor inputs. Resistor type spark plugs are used. Base ignition timing is not adjustable. By con- Spark plug resistance values range from 6,000 to trolling the coil ground circuit, the PCM is able to set 20,000 ohms (when checked with at least a 1000 volt the base timing and adjust the ignition timing spark plug tester). Do not use an ohmmeter to advance. This is done to meet changing engine oper- check the resistance values of the spark plugs. ating conditions. Inaccurate readings will result. The ignition coil is not oil filled. The windings are embedded in an epoxy compound. This provides heat OPERATION and vibration resistance that allows the ignition coil To prevent possible pre-ignition and/or mechanical to be mounted on the engine. engine damage, the correct type/heat range/number Spark plug cables (secondary wires or cables) are spark plug must be used. used with the 2.4L engine. Always use the recommended torque when tightening spark plugs. 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. 8I - 14 IGNITION CONTROL TJ SPARK PLUG (Continued)

Remove the spark plugs and examine them for with a rust colored deposit. This rust color can be burned electrodes and fouled, cracked or broken por- misdiagnosed as being caused by coolant in the com- celain insulators. Keep plugs arranged in the order bustion chamber. Spark plug performance may be in which they were removed from the engine. A sin- affected by MMT deposits. gle plug displaying an abnormal condition indicates that a problem exists in the corresponding cylinder. COLD FOULING/CARBON FOULING Replace spark plugs at the intervals recommended in Cold fouling is sometimes referred to as carbon Group O, Lubrication and Maintenance fouling. The deposits that cause cold fouling are basi- Spark plugs that have low mileage may be cleaned cally carbon (Fig. 23). A dry, black deposit on one or and reused if not otherwise defective, carbon or oil two plugs in a set may be caused by sticking valves fouled. Also refer to Spark Plug Conditions. or defective spark plug cables. Cold (carbon) fouling of the entire set of spark plugs may be caused by a CAUTION: Never use a motorized wire wheel brush clogged air cleaner element or repeated short operat- to clean the spark plugs. Metallic deposits will ing times (short trips). remain on the spark plug insulator and will cause plug misfire. WET FOULING OR GAS FOULING A spark plug coated with excessive wet fuel or oil is wet fouled. In older engines, worn piston rings, DIAGNOSIS AND TESTING - SPARK PLUG leaking valve guide seals or excessive cylinder wear CONDITIONS can cause wet fouling. In new or recently overhauled engines, wet fouling may occur before break-in (nor- NORMAL OPERATING mal oil control) is achieved. This condition can usu- The few deposits present on the spark plug will ally be resolved by cleaning and reinstalling the probably be light tan or slightly gray in color. This is fouled plugs. evident with most grades of commercial gasoline (Fig. 23). There will not be evidence of electrode OIL OR ASH ENCRUSTED burning. Gap growth will not average more than If one or more spark plugs are oil or oil ash approximately 0.025 mm (.001 in) per 3200 km (2000 encrusted (Fig. 24), evaluate engine condition for the miles) of operation. Spark plugs that have normal cause of oil entry into that particular combustion wear can usually be cleaned, have the electrodes chamber. filed, have the gap set and then be installed.

Fig. 23 Normal Operation and Cold (Carbon) Fouling 1 - NORMAL 2 - DRY BLACK DEPOSITS 3 - COLD (CARBON) FOULING

Some fuel refiners in several areas of the United Fig. 24 Oil or Ash Encrusted 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 TJ IGNITION CONTROL 8I - 15 SPARK PLUG (Continued) 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 subjected to a high torque load, deposits partially liq- uefy and bridge the gap between electrodes (Fig. 25). This short circuits the electrodes. Spark plugs with electrode gap bridging can be cleaned using standard procedures.

Fig. 26 Scavenger Deposits 1 - GROUND ELECTRODE COVERED WITH WHITE OR YELLOW DEPOSITS 2 - CENTER ELECTRODE

Fig. 25 Electrode Gap Bridging 1 - GROUND ELECTRODE 2 - DEPOSITS 3 - CENTER ELECTRODE

SCAVENGER DEPOSITS Fuel scavenger deposits may be either white or yellow (Fig. 26). They may appear to be harmful, but this is a normal condition caused by chemical addi- Fig. 27 Chipped Electrode Insulator tives in certain fuels. These additives are designed to 1 - GROUND ELECTRODE change the chemical nature of deposits and decrease 2 - CENTER ELECTRODE spark plug misfire tendencies. Notice that accumula- 3 - CHIPPED INSULATOR tion on the ground electrode and shell area may be heavy, but the deposits are easily removed. Spark PREIGNITION DAMAGE plugs with scavenger deposits can be considered nor- Preignition damage is usually caused by excessive mal in condition and can be cleaned using standard combustion chamber temperature. The center elec- procedures. trode dissolves first and the ground electrode dissolves somewhat latter (Fig. 28). Insulators appear CHIPPED ELECTRODE INSULATOR relatively deposit free. Determine if the spark plug A chipped electrode insulator usually results from has the correct heat range rating for the engine. bending the center electrode while adjusting the Determine if ignition timing is over advanced or if spark plug electrode gap. Under certain conditions, other operating conditions are causing engine over- severe detonation can also separate the insulator heating. (The heat range rating refers to the operat- from the center electrode (Fig. 27). Spark plugs with ing temperature of a particular type spark plug. this condition must be replaced. Spark plugs are designed to operate within specific temperature ranges. This depends upon the thick- ness and length of the center electrodes porcelain insulator.) 8I - 16 IGNITION CONTROL TJ SPARK PLUG (Continued) REMOVAL

2.4L If spark plug for #2 or #3 cylinder is being removed, throttle body must be removed. Refer to Throttle Body Removal. (1) Remove air cleaner tube and housing. (2) Twist secondary cable at cylinder head to break loose at spark plug. Remove cable from plug. (3) Prior to removing spark plug, spray com- pressed 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. Fig. 28 Preignition Damage (5) Inspect spark plug condition. Refer to Spark 1 - GROUND ELECTRODE STARTING TO DISSOLVE Plug Conditions. 2 - CENTER ELECTRODE DISSOLVED

SPARK PLUG OVERHEATING 4.0L On the 4.0L 6–cylinder engine the spark plugs are Overheating is indicated by a white or gray center located below the coil rail assembly. To gain access to electrode insulator that also appears blistered (Fig. any/all spark plug(s), refer to Ignition Coil-4.0L 29). The increase in electrode gap will be consider- Engine Removal/Installation. ably in excess of 0.001 inch per 2000 miles of opera- (1) Prior to removing the spark plug, spray com- tion. This suggests that a plug with a cooler heat pressed air around the spark plug hole and the area range rating should be used. Over advanced ignition around the spark plug. This will help prevent foreign timing, detonation and cooling system malfunctions material from entering the combustion chamber. can also cause spark plug overheating. (2) Remove the spark plug using a quality socket with a rubber or foam insert. (3) Inspect the spark plug condition. Refer to Spark Plugs Conditions.

CLEANING CLEANING SPARK PLUGS The plugs may be cleaned using commercially available spark plug cleaning equipment. After cleaning, file the center electrode flat with a small point file or jewelers file before adjusting gap.

CAUTION: Never use a motorized wire wheel brush to clean the spark plugs. Metallic deposits will Fig. 29 Spark Plug Overheating remain on the spark plug insulator and will cause plug misfire. 1 - BLISTERED WHITE OR GRAY COLORED INSULATOR TJ IGNITION CONTROL 8I - 17 SPARK PLUG (Continued) INSTALLATION SPARK PLUG CABLE Always tighten spark plugs to the specified torque. Over tightening can cause distortion. This may result DESCRIPTION in a change in the spark plug gap, or a cracked por- Spark plug cables are used only on the 2.4L 4–cyl- celain insulator. inder engine. They are sometimes referred to as sec- When replacing the spark plug and ignition coil ondary ignition wires. cables, route the cables correctly and secure them in the appropriate retainers. Failure to route the cables OPERATION properly can cause the radio to reproduce ignition 2.4L 4–cylinder engine only: The spark plug cables noise. It could cause cross ignition of the spark plugs, transfer electrical current from the ignition coil(s) or short circuit the cables to ground. and/or distributor, to individual spark plugs at each cylinder. The resistive spark plug cables are of non- 2.4L metallic construction. The cables provide suppression of radio frequency emissions from the ignition sys- CAUTION: Spark plug tightening on the 2.4L is tem. torque critical. The plugs are equipped with tapered seats. Do not exceed 15 ft. lbs. torque. DIAGNOSIS AND TESTING Special care should be taken when installing spark TESTING plugs into the cylinder head spark plug wells. Be sure the plugs do not drop into the plug wells as elec- Check the spark plug cable connections for good trodes can be damaged. contact at the coil(s) and spark plugs. Terminals Always tighten spark plugs to the specified torque. should be fully seated. The insulators should be in Over tightening can cause distortion resulting in a good condition and should fit tightly on the coil and change in the spark plug gap or a cracked porcelain spark plugs. Spark plug cables with insulators that insulator. are cracked or torn must be replaced. (1) Start the spark plug into the cylinder head by Clean high voltage ignition cables with a cloth hand to avoid cross threading. moistened with a non-flammable solvent. Wipe the (2) Tighten spark plugs. Refer to torque specifica- cables dry. Check for brittle or cracked insulation. tions. When testing secondary cables for damage with an (3) Install throttle body (if necessary). Refer to oscilloscope, follow the instructions of the equipment Throttle Body Installation. manufacturer. (4) Install air cleaner tube and housing. If an oscilloscope is not available, spark plug cables may be tested as follows: 4.0L CAUTION: Do not leave any one spark plug cable Special care should be taken when installing spark disconnected for longer than necessary during test- plugs into the cylinder head spark plug wells. Be ing. This may cause possible heat damage to the sure the plugs do not drop into the plug wells as elec- catalytic converter. Total test time must not exceed trodes can be damaged. ten minutes. Always tighten spark plugs to the specified torque. Over tightening can cause distortion resulting in a With the engine running, remove spark plug cable change in the spark plug gap or a cracked porcelain from spark plug (one at a time) and hold next to a insulator. good engine ground. If the cable and spark plug are (1) Start the spark plug into the cylinder head by in good condition, the engine rpm should drop and hand to avoid cross threading. the engine will run poorly. If engine rpm does not (2) Tighten spark plugs. Refer to torque specifica- drop, the cable and/or spark plug may not be operat- tions. ing properly and should be replaced. Also check (3) Install coil rail. Refer to Ignition Coil-4.0L engine cylinder compression. Engine Removal/Installation. With the engine not running, connect one end of a test probe to a good ground. Start the engine and run the other end of the test probe along the entire length of all spark plug cables. If cables are cracked or punctured, there will be a noticeable spark jump from the damaged area to the test probe. Cracked, damaged or faulty cables should be replaced with resistance type cable. This can be identified by the 8I - 18 IGNITION CONTROL TJ SPARK PLUG CABLE (Continued) words ELECTRONIC SUPPRESSION printed on the cable jacket. Use an ohmmeter to test for open circuits, excessive resistance or loose terminals. Remove the cable at ignition coil, and from spark plug. Connect ohmmeter to each end of cable. Resistance should be 250 to 1000 Ohms per inch of cable. If resistance is not within specifications as found in the SPARK PLUG CABLE RESISTANCE chart, replace the cable. Test all spark plug cables in this manner. SPARK PLUG CABLE RESISTANCE

MINIMUM MAXIMUM 250 Ohms Per Inch 1000 Ohms Per Inch 3000 Ohms Per Foot 12,000 Ohms Per Foot Fig. 30 CABLE REMOVAL REMOVAL - 2.4L 1 - SPARK PLUG CABLE AND BOOT 2 - SPARK PLUG BOOT PULLER CAUTION: When disconnecting a high voltage cable 3 - TWIST AND PULL 4 - SPARK PLUG from a spark plug or from the distributor cap, twist the rubber boot slightly (1/2 turn) to break it loose INSTALLATION (Fig. 30). (1) Push the cable firmly onto the sparkplug. (1) Grasp the boot (not the cable) and pull it off with a steady, even force.