1988 JEEP CHEROKEE width
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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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Page 70 of 1378
Cu. In. .......................................... 242
Liters ........................................... 4.0
Fuel System ........................................ MPI
HP@RPM ...................................... 173 @ 2500
Torque Ft. Lbs.@RPM ......................... 220 @ 2500
Compression Ratio ................................ 9.2:1
Bore ....................................... 3.88 (98.4)
Stroke ..................................... 3.44 (87.4)
4.2L
Displacement
Cu. In. .......................................... 258
Liters ........................................... 4.2
Fuel System ..................................... 2-Bbl.
HP@RPM ...................................... 112 @ 3000
Torque Ft. Lbs.@RPM ......................... 210 @ 2000
Compression Ratio ................................ 9.2:1
Bore ....................................... 3.75 (95.3)
Stroke ..................................... 3.90 (98.9)
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VALVE SPECIFICATIONS
VALVES SPECIFICATIONS TABLE \
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Application In. (mm)
4.0L
Intake
Head Diameter ........................... 1.91 (48.51)
Face Angle ....................................... 45
Seat Angle ..................................... 44.5
Seat Width ..................... .040-.060 (1.02-1.52)
Stem Diameter ............................ .312 (7.92)
Stem Clearance ................... .001-.003 (.03-.08)
Valve Lift .............................. .424 (10.76)
Exhaust
Head Diameter ........................... 1.50 (38.10)
Face Angle ....................................... 45
Seat Angle ..................................... 44.5
Seat Width ..................... .040-.060 (1.02-1.52)
Stem Diameter ............................ .312 (7.92)
Stem Clearance .................. .001-.003 (.03-.003)
Valve Lift .............................. .424 (10.76)
Valve Spring Height Installed ............ 1.625 (41.29)
4.2L
Intake
Head Diameter .................. 1.78-1.79 (45.3-45.5)
Face Angle ....................................... 29
Seat Angle ....................................... 30
Seat Width ..................... .040-.060 (1.02-1.52)
Stem Diameter ................ .3715-.3725 (9.44-9.46)
Stem Clearance ................... .001-.003 (.03-.08)
Valve Lift .............................. .405 (10.29)
Exhaust
Head Diameter .................. 1.40-1.41 (35.6-35.8)
Face Angle ....................................... 44
Seat Angle ..................................... 44.5
Seat Width ..................... .040-.060 (1.02-1.52)
Stem Diameter ................ .3715-.3725 (9.44-9.46)
Stem Clearance ................... .001-.003 (.03-.08)
Valve Lift .............................. .405 (10.29)
Valve Spring Height Installed ...................... ( 1)
Page 73 of 1378
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4.0 L C EC S YSTE M
1988 J e ep C hero ke e
1988 COMPUTERIZED ENGINE Controls
ENGINE CONTROL SYSTEM
JEEP 4.0L MPFI 6-CYLINDER
Cherokee, Comanche & Wagoneer
DESCRIPTION
The 4.0L engine control system controls engine operation to
lower exhaust emissions while maintaining good fuel economy and
driveability. The system is designed to maintain a 14.7:1 air/fuel
ratio under all engine operating conditions. When the ideal air/fuel
ratio is maintained, the catalytic converter can control oxides of
nitrogen (NOx), hydrocarbon (HC), and carbon monoxide (CO) emissio\
ns.
The system consists of the following sub-systems: Fuel
Control, Data Sensors and Switches, Electronic Control Unit (ECU),
Diagnostics, Electronic Spark Advance, Idle Speed Control, Exhaust Gas
Recirculation, and Transmission Shift Light.
OPERATION
FUEL CONTROL
The fuel control system delivers fuel to the engine. Fuel
from the in-tank fuel pump flows to the fuel rail, injectors and
pressure regulator. The pressure regulator maintains fuel system
pressure at 31-39 psi (2.l-2.7 kg/cm
). Excess fuel is returned to the
tank by a fuel return line.
The fuel pump is energized through the fuel pump relay that
is located on the right inner fender panel in the engine compartment.
Battery voltage is provided through the ignition switch and is
energized when the ECU completes the ground path.
The fuel injectors are electrically operated solenoid valves.
The ECU determines injector pulse width ("on/off") time based upon
engine operating conditions and delivers the proper pulse width to
maintain an air/fuel ratio of 14.7:l.
The ECU varies the amount of voltage applied to the injectors
to compensate for battery voltage changes. Battery voltage information
is provided to the ECU through the wiring harness. No sensor or switch
is required.
DATA SENSORS & SWITCHES
Each sensor and/or switch furnishes electronic impulses to
the ECM. Based on these input signals, the ECM computes spark timing
and air/fuel mixture for proper engine operation.
Coolant Temperature Sensor (CTS)
The CTS is located on the left side of the block, just below
exhaust manifold. The sensor provides coolant temperature information
to the ECU. Engine coolant temperature is used by the ECU for the
following functions:
* Enrich air/fuel mixture for cold engine starts.
* Control idle speed during warm-up.
* Increase spark advance during cold engine operation.
* Prevent EGR flow during cold engine operation.
Page 192 of 1378
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AN TI- L O CK B RAK E S A FE TY P R EC AU TIO NS
1988 J e ep C hero ke e
GENERAL INFORMATION
Anti-Lock Brake Safety Precautions
* PLEASE READ THIS FIRST *
This article is intended for general information purposes
only. This information may not apply to all makes and models. If
vehicle is equipped with Anti-Lock Brake System (ABS), refer to
appropriate ANTI-LOCK BRAKE SYSTEM article in the BRAKES section for
description, operation, depressurizing, testing, system bleeding,
trouble shooting and servicing of specific system.
WARNING: Failure to depressurize ABS could lead to physical injury.
ANTI-LOCK BRAKE SAFETY PRECAUTIONS
WARNING: Failure to depressurize ABS could lead to physical injury.
* NEVER open a bleeder valve or loosen a hydraulic line
while ABS is pressurized.
* NEVER disconnect or reconnect any electrical connectors
while ignition is on. Damage to ABS control unit may result.
* DO NOT attempt to bleed hyudarulic system without first
referring to the appropriate ANTI-LOCK BRAKE SYSTEM article
in the BRAKES section.
* Only use specially designed brake hoses/lines on ABS equipped
vehicles.
* DO NOT tap on speed sensor components (sensor, sensor rings).
Sensor rings must be pressed into hubs, NOT hammered into
hubs. Striking these components can cause demagnetization or
a loss of polarization, affecting the accuracy of the speed
signal returning to the ABS control unit.
* DO NOT mix tire sizes. Increasing the width, as long as tires
remain close to the original diameter, is acceptable. Rolling
diameter must be identical for all 4 tires. Some
manufacturers recommend tires of the same brand, style and
type. Failure to follow this precaution may cause inaccurate
wheel speed readings.
* DO NOT contaminate speed sensor components with grease. Only
use recommended coating, when system calls for an
anti-corrosion coating.
* When speed sensor components have been removed, ALWAYS check
sensor-to-ring air gaps when applicable. These specifications
can be found in each appropriate article.
* ONLY use rocommended brake fluids. DO NOT use silicone brake
fluids in an ABS equipped vehicle.
* When instlling transmittion devices (CB's, telephones, etc.)
on ABS equipped vehicles, DO NOT locate the antenna near the
ABS control unit (or any control unit).
* Disconnect all on-board computers, when using electric
welding equipment.
* DO NOT expose the ABS control unit to prolonged periods of
high heat (185
F/85 C for 2 hours is generally considered a
maximum limit).
Page 337 of 1378
![JEEP CHEROKEE 1988 Service Repair Manual \
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Application In. (mm)
Cheroke](/manual-img/16/57037/w960_57037-336.png "JEEP CHEROKEE 1988 Service Repair Manual \
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Application In. (mm)
Cheroke")
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Application In. (mm)
Cherokee, Comanche, Wagoneer & Wrangler
Drum Diameter ............................ 10.00 (254.0)
Drum Width ................................. 1.75 (44.5)
Max. Drum Refinish Diam. ................. 10.06 (255.5)
Wheel Cyl. Diameter ........................ .875 (22.2)
Master Cyl. Diameter ....................... .937 (23.8)
Grand Wagoneer
Drum Diameter ............................ 11.00 (279.4)
Drum Width ................................. 2.00 (50.8)
Max. Drum Refinish Diam. ................. 11.06 (280.9)
Wheel Cyl. Diameter ....................... .937 (23.80)
Master Cyl. Diameter ..................... 1.125 (28.58)
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Page 433 of 1378
9) If difficulty is encountered when making these
adjustments, horizontal alignment should be checked. Even though
vertical alignment is correct, horizontal alignment can be badly out
of adjustment. This is often found after major component replacement
or repair of serious accident damage. See Fig. 8.
Fig. 8: Horizontal Alignment of Drive Shaft
Plane of trunnions should be parallel.
10) To make horizontal alignment checks, set straightedges
up. See Fig. 9. Set transmission output flange horizontal and clamp
straightedge to flange in a horizontal plane. Repeat procedure with
drive pinion flange. Ensure that flanges are horizontal by checking
angle of straightedge with spirit level.
Fig. 9: Checking Horizontal Alignment
Measure at 6 points shown using straightedges and framing squares.
11) Using straightedge that is 12" longer than width of rear
wheel track at 90 degrees, clamp to frame side rails. Use large
Page 583 of 1378
remote vacuum regulator. The internal solenoid is normally open, which
causes the vacuum signal to be vented off to the atmosphere when EGR
is not controlled by the Electronic Control Module (ECM). The solenoid\
valve opens and closes the vacuum signal, controlling the amount of
vacuum applied to the diaphragm. See Fig. 12.
The electronic EGR valve contains a voltage regulator, which
converts ECM signal and regulates current to the solenoid. The ECM
controls EGR flow with a pulse width modulated signal based on
airflow, TPS and RPM. This system also contains a pintle position
sensor, which works similarly to a TPS sensor. As EGR flow is
increased, the sensor output increases.
Verify EGR valve is present and not modified or purposely
damaged. Ensure thermal vacuum switches, pressure transducers, speed
switches, etc., (if applicable) are not by-passed or modified. Ensure
electrical connector to EGR valve is not disconnected.
Fig. 12: Cutaway View Of Typical Integrated Electronic EGR Valve
Courtesy of General Motors Corp.
SPARK CONTROLS (SPK)