1988 JEEP CHEROKEE power steering

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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).\

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

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

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

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

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

"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 

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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ABBREVIATION DEFINITION 










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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