JEEP CHEROKEE 1988 Service User Guide
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Crankshaft End Play
1) Using dial indicator, check crankshaft end play. Inspect
crankshaft thrust surfaces or thrust bearing for wear if not within
specification. See ENGINE SPECIFICATIONS table.
2) Replace thrust bearing if required. When replacing thrust
bearing, pry crankshaft forward then reward prior to tightening main
bearing cap to specification. Recheck end play. Replace crankshaft if
not within specification.
REAR MAIN BEARING OIL SEAL
Removal
Remove transmission, clutch housing and flywheel or drive
plate. Using screwdriver, pry oil seal from housing. Avoid damage to
surrounding area.
NOTE: Shim must be used when installing old type oil seal Part No.
(324 1669) only. DO NOT use shim when installing new type
oil seal Part. No. (8933 004 143).
Installation
1) Position wing nut on Seal Installer (J-36306) until it
contacts the shaft nut. See Fig. 7. Install shim if old type seal Part
No. (324 1669) is used.
2) Lubricate inner and outer edges of seal. Install seal on
seal installer with seal dust shield toward the wing nut. Install seal
installer on crankshaft so pilot and dowel are positioned on the
crankshaft.
3) Thread the seal installer attaching screws into the
crankshaft and tighten. Rotate wing nut until it bottoms. This will
properly position the seal.
4) Remove seal installer. Ensure dust shield is not curled
under. Reverse removal procedures for remaining components.
Fig. 7: Installing Rear Main Bearing Oil Seal
WATER PUMP
Removal
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1) Drain cooling system. Remove fan shroud and drive belts.
Remove fan assembly.
2) Disconnect heater hoses and lower radiator hose at water
pump. Remove water pump retaining bolts. Remove water pump.
Installation
Clean all gasket surfaces. Install water pump. Tighten bolts
to specification. Ensure pump turns freely. Reverse removal
procedures. Fill and purge air from cooling system.
NOTE: It may be necessary to remove heater hose to remove trapped
air if system cannot be purged using following procedures.
Cooling System Air Purge (Vehicles With Coolant Recovery)
Fill system to proper level. Place heater control to "HEAT"
position and temperature control to "WARM" or "HIGH" position. Install
coolant caps. Operate engine to normal operating temperature. Shut off
engine and allow system to cool. Add coolant to recovery bottle.
Repeat procedure to obtain correct coolant level.
Cooling System Air Purge (Vehicles Without Coolant Recovery)
Fill system to proper level. Place heater control to "HEAT"
position and temperature control to "WARM" or "HIGH" position. Operate
engine to normal operating temperature with radiator cap removed. Add
necessary coolant and install radiator cap.
NOTE: For further information on cooling system capacities and
other cooling system components, see ENGINE COOLING SYSTEMS
article.
ENGINE OILING
CRANKCASE CAPACITY
Crankcase capacity is 4 qts. (3.8 L) with oil filter change.
NORMAL OIL PRESSURE
Normal oil pressure should be 13 psi (.91 kg/cm) at 600 RPM
or 37-75 psi (2.6-5.3 kg/cm) at 1600 RPM.
OIL PRESSURE REGULATOR VALVE
Oil pressure regulator valve is located in oil pump body and
is nonadjustable.
OILING SYSTEM
Engine lubrication is provided by the distributor driven
gear-type oil pump. Oil is supplied through the full-flow oil filter
and into an internal oil passage. Internal passage runs along right
side of block and intersects lifter bores.
Oil is then routed to camshaft and crankshaft bearings. Oil
is supplied to rocker arms from the hydraulic lifters and through the
push rods. By-pass valves are located in oil filter mounting and oil
pump.
OIL PUMP
Removal
Remove oil pan. See OIL PAN REMOVAL article. Remove oil pump
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retaining bolts.
CAUTION: DO NOT move oil pick-up pipe in pump body. If oil pick-up
pipe is moved, pick-up pipe must be replaced to ensure an
airtight seal.
Disassembly & Inspection
Disassemble pump. See Fig. 8. Inspect for wear or damage.
Using straightedge and feeler gauge, measure gear end clearance. See
Fig. 9 . Replace assembly if gear end clearance exceeds specification.
Measure gear-to-body clearance. Replace components as necessary if not
within specification. See OIL PUMP SPECIFICATIONS table.
CAUTION: If relief valve is replaced, ensure replacement valve is
the same diameter as that removed. Different diameter
valves may be used.
Reassembly & Installation
1) Reverse disassembly procedures. Apply Permatex No. 2 to
pick-up pipe prior to installation. Using Pipe Installer (J-21882),
install pick-up pipe. Ensure pick-up pipe support bracket is aligned
with pump cover bolt.
2) Fill pump cavity with petroleum jelly prior to installing
pump cover. Apply Loctite on pump cover area. Install cover and bolts.
Tighten bolts to specification. Check pump gears for freedom of
rotation.
3) Install oil pump and new gasket. Tighten retaining bolts
to specification.
OIL PUMP SPECIFICATIONS
OIL PUMP SPECIFICATIONS TABLE \
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Application In. (mm)
Gear End Clearance ................... .002-.006 (.05-.15)
Gear-to-Body Clearance ............... .002-.004 (.05-.10)
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Fig. 8: Exploded View of Oil Pump Assembly
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Fig. 9: Measuring Oil Pump Gear End Clearance
TORQUE SPECIFICATIONS
TORQUE SPECIFICATIONS TABLE \
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Application Ft. Lbs. (N.m)
Camshaft Sprocket Bolt .......................... 80 (109)
Connecting Rod Cap Nut ........................... 33 (45)
Cylinder Head Bolt
No. 8 ........................................ 100 (136)
All Others ................................... 110 (149)
Drive Plate-to-Converter Bolt .................... 22 (30)
EGR Valve Pipe Nut ............................... 30 (41)
Exhaust Manifold Bolt ............................ 23 (31)
Fan Bolt ......................................... 18 (24)
Flywheel-to-Crankshaft Bolt .................. ( 1) 50 (68)
Intake Manifold Bolt ............................. 23 (31)
Main Bearing Cap Bolt
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Step 1 ........................................ 40 (54)
Step 2 ........................................ 70 (95)
Step 3 ....................................... 80 (109)
Oil Pump Retaining Bolt
Short .......................................... 10 (14)
Long ........................................... 17 (23)
Oxygen Sensor .................................... 35 (47)
Pulley-to-Vibration Damper Bolt .................. 20 (27)
Rocker Arm Bolt .................................. 19 (26)
Throttle Body-to-Intake Bolt ..................... 16 (22)
Torque Converter Drive
Plate-to-Crankshaft Bolt .................... (1) 40 (54)
Vibration Damper Bolt ....................... ( 2) 80 (109)
Water Pump Bolt .................................. 13 (18)
INCH Lbs. (N.m)
Front Cover-to-Block
Bolt ............................................ 60 (7)
Stud .......................................... 192 (22)
Oil Pan Bolt
1/4" X 20 ....................................... 84 (9)
5/16" X 18 .................................... 132 (15)
Oil Pump Cover Bolt ............................... 70 (8)
Valve Cover Bolt .................................. 55 (5)
( 1) - Tighten to specification and an additional 60 degrees.
( 2) - With bolt cleaned and threads lubricated with oil.
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ENGINE SPECIFICATIONS
GENERAL ENGINE SPECIFICATIONS
GENERAL ENGINE SPECIFICATIONS TABLE \
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Application In. (mm)
Displacement
Cu. In. ............................................ 150
Liters ............................................. 2.5
Fuel System .......................................... TBI
HP @ RPM ...................................... 117 @ 5000
Torque Ft. Lbs. @ RPM ......................... 135 @ 3500
Compression Ratio .................................. 9.2:1
Bore ......................................... 3.88 (98.5)
Stroke ....................................... 3.19 (81.0)
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VALVE SPECIFICATIONS
VALVE SPECIFICATIONS TABLE \
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Application In. (mm)
Intake ( 1)
Head Diameter ................ 1.905-1.915 (48.38-48.60)
Face Angle ......................................... 44
Seat Angle ..................................... 44 30'
Seat Width ................... ( 2) .040-.060 (1.02-1.52)
Stem Diameter .................... .311-.312 (7.89-7.98)
Stem Clearance ..................... .001-.003 (.02-.08)
Valve Lift ................................ .424 (10.76)
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Exhaust (1)
Head Diameter ................ 1.495-1.505 (37.97-38.60)
Face Angle ......................................... 44
Seat Angle ..................................... 44 30'
Seat Width ................... ( 2) .040-.060 (1.02-1.52)
Stem Diameter .................... .311-.312 (7.89-7.98)
Stem Clearance ..................... .001-.003 (.02-.08)
Valve Lift ................................ .424 (10.76)
( 1) - Minimum valve margin is 1/32" (.78 mm).
( 2) - Maximum seal runout is .0025" (.084 mm).
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PISTON/PIN/RING SPECIFICATIONS
PISTONS, PINS & RINGS SPECIFICATIONS TABLE \
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Application In. (mm)
Piston Clearance ................. .0009-.0017 (.023-.043)
Pins
Piston Fit ..................... .0003-.0005 (.008-.013)
Rod Fit ...................................... Press Fit
Rings
Ring No. 1 & 2
End Gap .......................... .010-.020 (.25-.51)
Side Clearance ............... .0017-.0032 (.043-.081)
Ring No. 3
End Gap .......................... .010-.025 (.25-.64)
Side Clearance .................. .001-.008 (.03-.020)
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BEARING SPECIFICATIONS
CRANKSHAFT MAIN & CONNECTING ROD BEARINGS SPECS TABLE \
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Application In. (mm)
Main Bearings
Journal Diameter ......... 2.4996-2.5001 (63.489-63.502)
Clearance ....................... .0010-.0025 (.02-.063)
Thrust Bearing ................................... No. 2
Crankshaft End Play ............ .0015-.0065 (.038-.165)
Connecting Rod Bearings
Journal Diameter ......... 2.0934-2.0955 (53.172-53.225)
Clearance .......................... .001-.003 (.02-.08)
Side Play .............................010-.019 (.02-.48)
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VALVE SPRING SPECIFICATIONS
VALVE SPRINGS SPECIFICATIONS TABLE \
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Application In. (mm)
Free Length .................................. 1.82 (46.2)
Pressure ( 1)
Valve Closed ............... 66-74 @ 1.63 (30-34 @ 41.3)
Valve Open .............. 205-220 @ 1.20 (91-100 @ 30.5)
( 1) - Lbs. @ In. (Kg @ mm).
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CAMSHAFT SPECIFICATIONS
CAMSHAFT SPECIFICATIONS TABLE \
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Application In. (mm)
Clearance ............................. .001-003 (.02-.08)
Lobe Lift .................................... .265 (6.73)
No. 1 ........................ 2.029-2.030 (51.54-51.56)
No. 2 ........................ 2.019-2.020 (51.28-51.30)
No. 3 ........................ 2.009-2.010 (51.03-51.05)
No. 4 ........................ 1.999-2.000 (50.77-50.80)
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Page 18 of 1378
\0032.5 L C EC S YSTE M
1988 J e ep C hero ke e
1988 Computerized Engine Controls
JEEP 4-CYLINDER 2.5L TBI COMPUTERIZED EMISSION CONTROL
Cherokee, Comanche
DESCRIPTION
The computerized engine control system, used on 2.5L models
with throttle body fuel injection, is built around an electronic
control unit (ECU). The ECU is a microprocessor-based computer.
The major function of the system is to reduce emissions. It
accomplishes this through a series of 13 sensors or switches that
constantly monitor several engine conditions. See Fig. 16.
Fig. 1: Vacuum Diagram for Jeep 2.5L CEC System
The computer processes input information from the sensors to
get an accurate picture of engine operation. It then provides output
control signals to regulate air/fuel ratio, ignition, idle speed and
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emission control devices. This permits optimum engine performance
with minimum emissions.
OPERATION
The engine control system is divided into 6 sub-systems:
electronic control unit (also called the ECU or computer), sensors and\
switches, fuel control, emission control, idle speed control, and
ignition advance control.
ELECTRONIC CONTROL UNIT (ECU)
The ECU is located under the instrument panel, above the
accelerator pedal. It receives information from the 13 engine sensors
or switches to determine engine operating conditions at any particular
moment. The ECU responds to these signals by sending a control signal
to the fuel injector, fuel pump, ignition control module, idle speed
actuator (ISA) motor, EGR solenoid, and canister purge solenoid. It
also controls the Load Swap relay, and on Man. Trans. models, the up-
shift indicator lamp.
SENSORS & SWITCHES
Exhaust Gas Oxygen (EGO) Sensor
The amount of oxygen in exhaust gases varies according to the
air/fuel ratio of the intake charge. The exhaust gas oxygen sensor,
located in the exhaust pipe, detects this content and transmits a low
voltage signal to the ECU.
The outer surface of the sensor is exposed to exhaust gases,
the inner surface to outside air. The difference in the amount of
oxygen contacting the inner and outer surfaces of the sensor creates a
pressure, which results in a small voltage signal. This signal, which
is a measure of the unburned oxygen in the exhaust gas, is transmitted
to the ECU.
If the amount of oxygen in the exhaust system is low (rich
mixture), the sensor voltage signal will be high. If the mixture is
lean, the oxygen sensor will generate a low voltage signal.
The sensor has a heating element that keeps the sensor at
proper operating temperature during all operating modes.
Manifold Air/Fuel Temperature (MAT) Sensor
The manifold air/fuel temperature sensor is installed in the
intake manifold. This sensor provides a voltage signal to the ECU
representing the temperature of the air/fuel mixture in the intake
manifold. The ECU compensates for air density changes during high
temperature operation.
Coolant Temperature Sensor (CTS)
The coolant temperature sensor is located in the intake
manifold coolant jacket. This sensor provides a voltage signal to the
ECU. The ECU uses this signal to determine engine temperature. During
cold engine operation, the ECU responds by enriching the air/fuel
mixture delivered to the injector, compensating for fuel condensation
in the intake manifold, controlling engine warm-up speed, increasing
ignition advance, and inhibiting operation of the EGR system.
Manifold Absolute Pressure (MAP) Sensor
The MAP sensor detects absolute pressure in the intake
manifold as well as ambient atmospheric pressure. This information is
supplied to the ECU, through voltage signals, as an indication of
engine load. The sensor is attached to the plenum chamber near the
hood latch. A vacuum line from the throttle body supplies the sensor
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with manifold pressure information.
Knock Sensor
The knock (detonation) sensor, located in the cylinder head,
provides an input signal to the ECU whenever detonation occurs. The
ECU then retards ignition advance to eliminate the detonation at the
applicable cylinders.
Speed Sensor
The speed sensor (or crankshaft position sensor) is mounted
at the flywheel/drive plate housing. The sensor detects the flywheel/
drive plate teeth as they pass during engine operation and sends an
electrical signal to the ECU, which calculates engine speed.
The flywheel/drive plate has a large trigger tooth and notch
located 90
and 12 small teeth before each top dead center (TDC)
position. When a small tooth or notch pass the magnetic core in the
sensor, the build-up and collapse of the magnetic field induces a
small voltage signal in the sensor pick-up windings.
The ECU counts these signals representing the number of teeth
as they pass the sensor. When a larger trigger tooth and notch pass
the magnetic core, a higher voltage signal is sent to the ECU. This
indicates to the ECU that a piston will be at the TDC position 12
teeth later. The ECU either advances or retards ignition timing as
necessary according to sensor inputs.
Battery Voltage
Battery voltage input to the ECU ensures that proper voltage
is applied to the injector. The ECU varies voltage to compensate for
battery voltage fluctuations.
Starter Motor Relay
The engine starter motor relay provides an input to the ECU,
indicating the starter motor is engaged.
Wide Open Throttle (WOT) Switch
The WOT switch is mounted on the side of the throttle body.
The switch provides a voltage signal to the ECU under wide open
throttle conditions. The ECU responds to this signal by enriching the
air/fuel mixture delivered to the injector.
Closed Throttle (Idle) Switch
This switch is integral with the idle speed actuator (ISA)
motor. The switch provides a voltage signal to the ECU, which
increases or decreases the throttle stop angle in response to engine
operating conditions.
Transmission Gear Position Indicator
The gear position indicator is mounted on vehicles equipped
with automatic transaxles. It provides a signal to the ECU to
indicate that the transaxle is in a driving mode and not in Park or
Neutral.
Power Steering Pressure Switch
The switch increases the idle speed during periods of high
power steering pump load and low engine RPM.
A/C Switch
The A/C switch sends a signal to the ECU when the air
conditioner is operating and when the compressor clutch must be
engaged to lower the temperature. The ECU, in turn, increases engine
speed to compensate for the added load of the air conditioner.
FUEL CONTROL