steering JEEP CHEROKEE 1988 Service Repair Manual
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Page 1 of 1378
![JEEP CHEROKEE 1988 Service Repair Manual \003
2.5 L 4 -C YL - V IN [ H ]
1 988 J e ep C hero ke e
1988 CHRYSLER MOTORS ENGINES
2.5L 4-Cylinder
Jeep: Cherokee, Comanche, Wagoneer, Wrangler
ENGINE](/img/16/57037/w960_57037-0.png "JEEP CHEROKEE 1988 Service Repair Manual \003
2.5 L 4 -C YL - V IN [ H ]
1 988 J e ep C hero ke e
1988 CHRYSLER MOTORS ENGINES
2.5L 4-Cylinder
Jeep: Cherokee, Comanche, Wagoneer, Wrangler
ENGINE")
\003
2.5 L 4 -C YL - V IN [ H ]
1 988 J e ep C hero ke e
1988 CHRYSLER MOTORS ENGINES
2.5L 4-Cylinder
Jeep: Cherokee, Comanche, Wagoneer, Wrangler
ENGINE CODING
ENGINE IDENTIFICATION
NOTE: For engine repair procedures not covered in this article,
see ENGINE OVERHAUL PROCEDURES - GENERAL INFORMATION article
in the GENERAL INFORMATION section.
The Vehicle Identification Number (VIN) is located on the
upper left side of dash, visible through windshield. The fourth
character of the VIN identifies the engine size. The tenth character
identifies the model year.
ENGINE IDENTIFICATION CODES TABLE
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Application VIN Code
2.5L 4-Cylinder TBI .................................... H
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SPECIAL ENGINE MARKS
Some engines are produced at the factory with oversize or
undersize components. These engines are identified by a letter code
stamped between ignition coil and distributor. Letters are decoded as
follows:
* "B" indicates all cylinder bores .010" (.25 mm) oversize.
* "C" indicates all camshaft bearing bores .010" (.25 mm)
oversize.
* "M" indicates all main bearing journals .010" (.25 mm)
undersize.
* "P" indicates all connecting rod journals .010" (.25 mm)
undersize.
REMOVAL & INSTALLATION
ENGINE REMOVAL
See ENGINE REMOVAL article.
INTAKE & EXHAUST MANIFOLDS
NOTE: Throttle body removal is necessary prior to manifold
removal. Throttle body can be separated from the manifold
and secured in a designated area with vacuum hoses attached.
Removal
1) Disconnect negative battery cable. Remove air cleaner, EGR
pipe and PCV hose. Disconnect and mark all vacuum hoses and electrical
connections. Drain cooling system.
2) Remove coolant hoses from intake manifold. Remove A/C
compressor and power steering pump and mounting bracket (if equipped).\
Page 20 of 1378
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
Page 24 of 1378
Fig. 4: Location of ECU-Controlled Relays
Load Swap Relay
The Load Swap Relay is used on models with A/C and power
steering. The relay works in conjunction with the power steering
pressure switch to disengage the A/C compressor clutch.
If the compressor clutch is engaged when the power steering
pressure switch contacts close, the input signal from the switch to
the ECU also activates the load swap relay. The relay contacts open,
cutting off electrical feed to the compressor clutch. The clutch
remains disengaged until the pressure switch contacts reopen and
engine idle returns to normal.
NOTE: The load swap relay does not reengage the compressor clutch
immediately. The relay has a timer that delays energizing
the clutch for .5 second to ensure smooth engagement.
Fuel Pump Control Relay
Battery voltage is applied to the relay through the ignition
switch. The relay is energized when a ground is provided by the ECU.
When energized, voltage is applied to the fuel pump See Fig. 15.
A/C Clutch Relay
Page 56 of 1378
from intake manifold. Disconnect fuel lines at fuel rail. Fuel lines
are removed by squeezing the 2 retaining tabs against the fuel line
and pulling the fuel line from the connector. Use caution as these
fuel lines are under pressure.
3) Loosen drive belt tensioner and remove drive belt. Remove
power steering pump and bracket from intake manifold. Remove fuel rail
retaining bolts. Remove fuel rail and injector assembly.
4) Remove intake manifold heat shield. Disconnect EGR tube
fittings. Disconnect exhaust pipe from manifold. Disconnect oxygen
sensor. Remove retaining bolts and remove manifolds.
Installation
1) Install new gasket. Install exhaust and intake manifolds
and loosely install bolts. Install EGR tube between manifolds. Tighten
manifold bolts in proper sequence see Fig. 1. Tighten to
specifications, see TORQUE SPECIFICATIONS TABLE in this article.
2) Tighten EGR tube bolts. Apply anti-seize to oxygen sensor
threads prior to installation. Reverse removal procedures for
remaining components. Tighten bolts to specification.
3) Install new "O" rings on fuel line connectors prior to
installation. Ensure "CLICK" sound is heard when installing fuel
lines. This indicates that fuel lines are properly seated.
Fig. 1: Manifold Tightening Sequence (4.0L)
Courtesy of Chrysler Motors.
INTAKE & EXHAUST MANIFOLD (4.2L)
Removal
1) Remove air cleaner. Disconnect fuel line at carburetor.
Mark and disconnect all vacuum hoses, ventilation hoses and electrical
connectors at intake manifold.
2) Disconnect throttle cable at bellcrank. On A/T models,
disconnect throttle valve rod. On all models, remove PCV hose from
manifold. Drain cooling system. Remove coolant hoses from intake
Page 57 of 1378
manifold.
3) Remove EGR tube fittings from manifolds. Remove power
steering pump and A/C compressor and mounting brackets (if equipped).
4) Remove intake manifold bolts. Remove intake manifold. If
exhaust manifold requires removal, disconnect exhaust pipe from
manifold. Remove oxygen sensor (if equipped). Remove exhaust manifold.\
Installation
1) Install new gasket. Install exhaust manifold and loosely
install bolts. Install intake manifold. Tighten bolts to specification
in proper sequence. See Fig. 2.
2) Apply anti-seize to oxygen sensor threads prior to
installation. Reverse removal procedure for remaining components.
Tighten bolts to specification. Fill and purge cooling system. See
COOLING SYSTEM AIR PURGE under WATER PUMP in this article.
Fig. 2: Manifold Tightening Sequence (4.2L)
Courtesy of Chrysler Motors.
CYLINDER HEAD
Removal
1) Disconnect negative battery cable. Drain cooling system.
Disconnect hoses at thermostat housing. Remove intake and exhaust
manifolds. See the following:
* INTAKE & EXHAUST MANIFOLD (4.0L) .
* INTAKE & EXHAUST MANIFOLD (4.2L) .
2) Disconnect and mark all hoses and electrical connections
at cylinder head. Disconnect and mark spark plug wires. Remove spark
plugs. Remove valve cover bolts.
3) Remove the rocker arms and the push rods. Remove cylinder
head bolts. Remove cylinder head. See ROCKER ARMS & BRIDGE.
Inspection
Inspect cylinder head for cracks or damage. Using
straightedge, check cylinder head for warpage in several areas. Repair
Page 67 of 1378
Removal
Drain cooling system. Disconnect radiator and heater hoses
from pump. Remove drive belt(s). Remove fan shroud. Remove fan
assembly. Remove electric cooling fan (if equipped). Remove power
steering bracket from water pump. Remove water pump and gasket.
Installation
Ensure gasket surfaces are clean. 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 W/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 W/O 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 systems, see appropriate
article in the ENGINE COOLING section.
LUBRICATION
CRANKCASE CAPACITY
Crankcase capacity for 4.0L is 5 1/2 qts. (5.2L) or 5 qts.
(4.7L) for 4.2L with oil filter change.
NORMAL OIL PRESSURE
Normal oil pressure should be 37-75 psi (2.6-5.3 kg/cm)
maximum above 1600 RPM. Minimum oil pressure should be 13 psi (.9
kg/cm
) at 600 RPM.
OIL PRESSURE REGULATOR VALVE
Oil pressure regulator valve is located in pump body. Valve
is nonadjustable and serviced as an assembly.
ENGINE 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 provides oil to the
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.
OIL PUMP
Removal
Remove oil pan. See OIL PAN REMOVAL in this section. Remove
Page 76 of 1378
These small voltage spikes give the ECU information for calculating
engine speed.
When a large tooth and notch pass the magnetic core of the
sensor, the concentration and collapse of the magnetic field created
induces a higher voltage spike into the sensor pick-up coil windings.
This higher voltage spike indicates to the ECU that a piston will soon
be at TDC (12 teeth later).
The ECU uses speed sensor information for advancing or
retarding ignition timing, dependent upon input from other sensors and
switches.
A/C "ON" Switch
This switch signals the ECU that the A/C system is energized.
This signal is used by the ECU to increase idle speed.
Starter Motor Relay
Although no switch or sensor is used, the ECU requires this
information for fuel enrichment during starting. This information is
passed on the the ECU through the starter motor relay.
Distributor Reference Signal
Although no switch or sensor is used, the ECU requires this
information for ignition timing and fuel supply. This information is
relayed to the ECU through a "synch pulse" provided by the distributor
stator. This allows the ECU to synchronize injector opening with
intake valve opening.
ELECTRONIC CONTROL MODULE (ECM)
The Electronic Control Unit (ECU) is the "brain" of the
engine control system. The ECU is located in the passenger
compartment, under left side of dash to right of steering column.
The ECU senses engine operating conditions, processes input
signals, and controls the various systems that affect vehicle
performance.
DIAGNOSTICS
The engine control system has diagnostic capabilities. Using
System Tester (M.S. 1700), diagnostics can be performed on the system
to more accurately determine faulty components. The diagnostic
connectors are located in the engine compartment at the right shock
tower (or under left side of instrument panel).
NOTE: Information for diagnosing the engine control system using
the System Tester (M.S. 1700) was not available from
manufacturer. Only component testing is provided.
ELECTRONIC SPARK ADVANCE
Based upon engine operating conditions received from the
sensors and switches, the ECU controls spark timing. The ECU triggers
the ignition coil through the ignition control module.
IDLE SPEED CONTROL
Idle speed is controlled by the ECU through the idle speed
stepper motor. A latch relay is used to program the stepper motor for
engine start-up. The relay is located on the right inner fender panel.
See Fig. 1 . The ECU energizes the latch relay when engine is in
cranking mode, and keeps the relay energized for 3-5 seconds after the
engine is stopped. In this way, the stepper motor can provide the
Page 97 of 1378
![JEEP CHEROKEE 1988 Service Repair Manual "P" ABBREVIATION TABLE
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"P" ABBREVIATION TABLE
"P" ABBREVIATION TABLE \
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ABBREVIATION DEFINITION
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"P" Park
P/C Printed Circuit
P/N Park/Neutral
P/S Power Steering
PAV Pulse Air Valve
PC-SOL Purge Control Solenoid
PCM Powertrain Control Module
PCS Purge Control Solenoid
PCSDM Passenger Compartment Sensor/Diagnostic Module
PCV Positive Crankcase Ventilation
PFE Pressure Feedback EGR sensor or circuit
PFI Port Fuel Injection (see MA SEFI)
PGM-CARB Programmed Carburetor
PGM-FI Programmed Fuel Injection
PIP Profile Ignition Pickup
PNK Pink
PPL Purple
PRNDL Park Reverse Neutral Drive Low
PROM Programmable Read-Only Memory
psi Pounds Per Square Inch
PSPS Power Steering Pressure Switch
PTC Positive Temperature Coefficient
PTO Power Take-Off
PWR GND Power Ground circuit
Pkg. Package
Press. Pressure
Prog. Programmed or Programmable
Pts. Pints
Pwr. Power
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"Q" ABBREVIATION TABLE
"Q" ABBREVIATION TABLE \
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ABBREVIATION DEFINITION
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Qts. Quarts
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"R" ABBREVIATION TABLE
"R" ABBREVIATION TABLE \
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ABBREVIATION DEFINITION
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RABS Rear Anti-Lock Brake System
RAC Remote Accessory Control
RAM Random Access Memory
RAP Retained Accessory Power
RECIRC Recirculation
RED Red
RH Right Hand
ROM Read Only Memory
RPM Revolutions Per Minute
Page 98 of 1378
RVB Rear Vacuum Break
RWAL Rear Wheel Anti-Lock Brake
RWD Rear Wheel Drive
Recirc. Recirculate or Recirculation
Reg. Regulator
Rly. Relay
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"S" ABBREVIATION TABLE
"S" ABBREVIATION TABLE \
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ABBREVIATION DEFINITION
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SAW Spark Angle Word
SBC Single Bed Converter
SBEC Single Board Engine Controller
SC Super Charged
SCC Spark Control Computer
SCS Air Suction Control Solenoid
SDM Supplemental Restraint System Diagnostic Module
SDU SRS Diagnostic Unit
SEN Sensor
SES Service Engine Soon
SFI Sequential (Port) Fuel Injection
SIG RTN Signal Return circuit
SIL Shift Indicator Light
SIR Supplemental Inflatable Restraint
SMEC Single Module Engine Controller
SOHC Single Overhead Cam
SOL or Sol. Solenoid
SPFI Sequential Port Fuel Injection
SPK Spark Control
SPOUT Spark Output Signal
SRS Supplemental Restraint System (Air Bag)
SS 3/4-4/3 Shift Solenoid circuit
SSI Solid State Ignition
STAR Self-Test Automatic Readout
STI Self Test Input circuit
STO Self-Test Output
SUB-O2 Sub Oxygen Sensor
Sen. or Sens. Sensor
Sol. Solenoid
Sprchg. Supercharger
Strg. Steering
Susp. Suspension
Sw. Switch
Sys. System
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"T" ABBREVIATION TABLE
"T" ABBREVIATION TABLE \
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ABBREVIATION DEFINITION
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T.V. Throttle Valve
TAB Thermactor Air By-Pass
TAC Thermostatic Air Cleaner
TAD Thermactor Air Diverter
TAN Tan
TBI Throttle Body Injection
Page 99 of 1378
TCC Torque Converter Clutch
TCCS Toyota Computer Control System
TDC Top Dead Center
TDCL Total Diagnostic Communication Link
TFI Thick Film Ignition system
TGS Top Gear Switch (cancels SIL in top gear)
THERMAC Thermostatic Air Cleaner
THS Transmission Hydraulic Switch
TP/TPS Throttle Position Sensor
TPI Tuned Port Injection
TPS Throttle Position Sensor/Switch
TS Temperature Sensor
TSB Technical Service Bulletin
TTS Transmission Temperature Switch
TV Thermovalve
TWC Three-Way Catalyst
Temp. Temperature
Trans. Transaxle/Transmission
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"V" ABBREVIATION TABLE
"V" ABBREVIATION TABLE \
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V Valve
VAF Vane Air Flow sensor or circuit
VAPS Variable Assist Power Steering
VAT Vane Air Temperature
VATS Vehicle Anti-Theft System
VBATT Vehicle Battery Voltage
VCC Viscous Converter Clutch
VIN Vehicle Identification Number
VIO Violet
VLR Volt Loop Reserve
VM Vacuum Modulator
VM Vane Meter
VOM Volt-Ohmmeter (Analog)
VPWR Vehicle Power supply voltage (10-14 volts)
VREF Voltage Reference (ECA supplied reference voltage
VRV Vacuum Regulator Valve
VSC Vehicle Speed Control sensor or signal
VSS Vehicle Speed Sensor or signal
VSV Vacuum Switching Valve
Vac. Vacuum
Volt. Voltage
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"W" ABBREVIATION TABLE
"W" ABBREVIATION TABLE \
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ABBREVIATION DEFINITION
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W/ With
W/O Without
WAC WOT A/C Cut-off switch or circuit
WAC Wide Open Throttle A/C Switch
WHT White
WOT Wide Open Throttle
YEL Yellow