1988 JEEP CHEROKEE battery

VALVE SPRING
Valve springs can be removed without removing cylinder head.
Valve Spring Installed
For 4.0L the Valve Spring Installed Height Specification is
1.625 inches or 41.29 mm. For the 4.2L the information is not
available from manufacturer.
HYDRAULIC VALVE LIFTER
Removal
Remove cylinder head. See CYLINDER HEAD. Using Lifter
Remover/Installer (J-21884), remove lifter. Mark lifter location for
reassembly reference. Replace lifters as an assembly if damaged.
Internal components cannot be interchanged.
Inspection
Inspect lifter and camshaft mating surfaces for wear. Check
cylinder block lifter bore diameter. Lifter bore diameter should be
within .9055-.9065" (22.999-23.025 mm). Replace parts as necessary.
Installation
Soak lifter assembly in engine oil prior to installation.
Reverse removal procedure for installation. Install lifter in original
location.
ENGINE FRONT COVER
Removal
1) Disconnect negative battery cable. Remove drive belts, fan
and hub assembly. Remove pulley from vibration damper. Remove
vibration damper retaining bolt and washer.
2) Using Puller (J-21719-01), remove vibration damper and
key. Remove alternator and A/C compressor bracket (if equipped).
Remove oil pan-to-front cover bolts. Remove cover-to-block retaining
bolts. Remove front cover.
3) Cut oil pan gasket tabs even with face of cylinder block.
Remove tabs. Remove gasket from oil pan. Pry crankshaft oil seal from
cover.
Installation
1) Ensure all gasket surfaces are clean. Ensure oil slinger
is installed on crankshaft. Apply sealing compound on both sides of
front cover gasket. Install gasket on cylinder block. Replace front
section of oil pan seal with similar section fabricated from new seal.
2) Coat seal with RTV sealant and place in position. Apply
sealant to the joint area of oil pan and cylinder block. Apply engine
oil on seal-to-oil pan contact areas.
3) Place front cover on cylinder block. Place Front Cover
Seal Installer (J-22248) in front cover seal area. Install all
retaining bolts. Tighten bolts to specification.
4) Install front cover oil seal. See FRONT COVER OIL SEAL in
this article. Remove front cover seal installer. Reverse removal
procedure for remaining components. Lubricate vibration damper
retaining bolt with oil prior to installation. Tighten bolts to
specification.
FRONT COVER OIL SEAL
1) Remove vibration damper. Pry seal from front cover. Use

\003
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.

proper increased enrichment for the next engine start. Idle speed is
nonadjustable.
EMISSION CONTROL
The ECU electrically controls Exhaust Gas Recirculation (EGR).\
An ECU-controlled solenoid valve is used to control EGR valve
function. This valve is located on the left inner fender panel and is
operated by the ECU in response to coolant temperature, throttle
position, and manifold pressure.
Under conditions of engine warm-up, engine idle, wide open
throttle, or rapid acceleration/deceleration, the solenoid valve is
energized, blocking vacuum to the EGR valve. At normal operating
temperatures with engine speed above idle, the solenoid valve is de-
energized, allowing normal EGR valve function.
NOTE: If the electrical connector is removed from the EGR solenoid,
EGR flow will be allowed at all times.
A/C CLUTCH CONTROL
The ECU controls the A/C compressor clutch to improve idle
quality. The A/C compressor clutch will be engaged or disengaged as
deemed necessary by the ECU through the A/C clutch relay.
SHIFT LIGHT CONTROL
The shift light system is used on all manual transmission
equipped vehicles. The ECU monitors coolant temperature, throttle
position, vehicle speed, and engine speed to control the shift light.
The ECU calculates what gear position the vehicle should be in and
uses this information to turn on the light. The light indicates the
best shift point to the driver for maximum fuel economy.
The light is tested when the ignition switch is turned on.
When the engine is started, the light should go out. A transmission-
mounted switch prevents the light from illuminating when the
transmission is shifted into high gear. The ECU turns the light off if
the shift to the next higher gear is not performed within 3-5 seconds
after light comes on.
DIAGNOSIS & TESTING
PRELIMINARY CHECKS
Before assuming that the ECU is faulty, the following systems
and components must be in good condition and operating properly:
* Air filter.
* All support systems and wiring.
* Battery connections and specific gravity.
* Compression pressure.
* Electrical and vacuum connections to components, sensors and
switches.
* Emission control devices.
* Ignition system.
* All vacuum and fuel line (hose) connections.
FUEL SYSTEM TEST
Fuel Pressure
1) Remove cap from pressure test port on fuel rail and

If no continuity is shown, repair wiring harness. If
continuity is shown, reconnect voltmeter as in step 2).
5) While observing voltmeter, crank engine. Voltmeter needle
should fluctuate back and forth during engine cranking. This verifies
proper operation of distributor stator. If voltmeter needle does not
fluctuate, replace stator.
EGR Solenoid Valve
1) Make sure vacuum is present at port "C" of the solenoid.
See Fig. 6 . Remove vacuum connector from ports "A" and "B" of
solenoid. Connect vacuum gauge to port "B". Start engine and run at
idle. Vacuum should not be present at port "B".
2) Disconnect electrical connector from solenoid. Vacuum
should now be present at port "B". Stop engine. Reconnect electrical
connector at solenoid. Remove vacuum gauge and reconnect vacuum hoses.
Relays - General Testing
1) The relays used on the 4.0L engine are all of the same
basic construction and design. Terminal No. 30 is usually connected to
battery voltage ("switched" or battery positive at all times).
Terminal No. 87A is connected to terminal No. 30 in de-energized
position.
2) Terminal No. 87 is connected to terminal No. 30 in the
energized position. This connection supplies battery voltage to the
operated device.
3) Terminal No. 86 is connected to the electromagnet of the
operated device; usually through a "switched" power source. Terminal
No. 85 is connected to the electromagnet of the operated device;
usually grounded through a switch or the ECU.
NOTE: Not all relays have battery voltage applied at terminal No.
30. Some may have battery voltage applied at terminal Nos. 87
or 87A. Check design of relay before testing.
4) When testing relays, there should be continuity between
terminal Nos. 87A and 30 when relay is in de-energized position.
Resistance between terminal Nos. 85 and 86 should be 70-80 ohms for
resistor-type relays and 81-91 ohms for diode-type relays.
Fig. 6: Testing EGR Solenoid Valve
Starter Motor Relay
1) Disconnect electrical connectors from terminals "I" and
"G". Using an ohmmeter, measure resistance between the terminals.

Resistance value should be about 22 ohms. Measure resistance between
either terminal and battery negative post. Resistance value should be
infinite. If resistance values are not as specified, replace relay. If
okay, reconnect electrical connectors.
2) Disconnect electrical connector from "SOL" terminal.
Connect voltmeter between terminal and battery negative post. While
observing voltmeter, turn ignition switch to "START" position. If 12
volts is not indicated, check and repair wiring harness, bulkhead
connector, and/or ignition switch. If battery voltage is present, go
to next step.
3) If battery voltage is present, but starter relay does not
work, place transmission in Park (Neutral for man. trans.) and apply
parking brake. Disconnect electrical connector from terminal "I" (Dark
Green wire) and apply battery voltage to terminal. Using a jumper
wire, touch terminal "G" to ground. If relay does not click, replace
relay. If relay does click, repair ground circuit.
Fig. 7: Design & Function of Relays
REMOVAL & INSTALLATION









\









\








\









\









\









\









\






 
ABBREVIATION DEFINITION 










\








\b
\









\









\









\









\









\






B/P Backpressure 

BAC By-Pass Air Control 

BAP Barometric Absolute Pressure Sensor 

BARO Barometric 

BBDC Before Bottom Dead Center 

BCM Body Control Module 

BDC Bottom Dead Center 

BHP Brake Horsepower 

BLK Black 

BLU Blue 

BMAP Barometric & Manifold Absolute Pressure Sensor 

BOO Brake On-Off Switch 

BP Barometric Pressure sensor 

BPS Barometric Pressure Sensor 

BPT Backpressure Transducer 

BRN Brown 

BTDC Before Top Dead Center 

BTU British Thermal Unit 

BVSV Bimetallic Vacuum Switching Valve 

Baro. Barometric 

Batt. Battery 

Bbl. Barrel (Example: 4-Bbl.) 

Blst. Ballast 

Blwr. Blower 

Brkr. Breaker 











\








\









\









\









\









\









\





\f

"C" ABBREVIATION TABLE
"C" ABBREVIATION TABLE







\









\








\









\









\









\









\








ABBREVIATION DEFINITION 










\








\b
\









\









\









\









\









\






C Celsius (Degrees) 

C(3) I Computer Controlled Coil Ignition 

C(4) Computer Controlled Catalytic Converter 

CANP Canister Purge solenoid 

CARB California Air Resources Board 

CAT Catalytic Converter 

CB Circuit Breaker 

CBD Closed Bowl Distributor 

CBVV Carburetor Bowl Vent Valve 

cc Cubic Centimeter 

CCC Computer Command Control 

CCD Computer Controlled Dwell 

CCM Central Control Module 

CCO Converter Clutch Override 

CCOT Cycling Clutch Orifice Tube 

CCW Counterclockwise 

CDI Capacitor Discharge Ignition 

CEC Computerized Engine Control 

CFI Central Fuel Injection 

CID Cubic Inch Displacement 

CID Cylinder Identification sensor 

CIS Continuous Injection System 

CIS-E Continuous Injection System-Electronic 

CKT Circuit 

CLR Clear 

CNG Compressed Natural Gas 

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 











\








\









\









\









\









\









\





\f

"V" ABBREVIATION TABLE
"V" ABBREVIATION TABLE







\









\








\









\









\









\









\






 
ABBREVIATION DEFINITION 










\








\b
\









\









\









\









\









\






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 











\








\









\









\









\









\









\





\f

"W" ABBREVIATION TABLE
"W" ABBREVIATION TABLE







\









\








\









\









\









\









\








ABBREVIATION DEFINITION 










\








\b
\









\









\









\









\









\






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 

Discharge system (slowly to prevent loss of compressor oil)
using approved refrigerant recovery/recycling equipment. Disconnect
evaporator and condenser lines from receiver-drier. Detach mounting
screws from receiver-drier bracket. Remove receiver-drier.
Installation
To install, reverse removal procedure. Evacuate, leak test,
recharge. Check A/C system for proper operation.
Fig. 1: Exploded View of Wrangler Evaporator Housing
Courtesy of Chrysler Motors.
EVAPORATOR-BLOWER HOUSING &
HEATER & EVAPORATOR CORES
NOTE: The following procedures are for vehicles with A/C-heater
systems only. For replacement of heater cores on vehicles
with heater systems only, see HEATER SYSTEMS, JEEP article.
Removal (Cherokee, Comanche & Wagoneer)
1) Disconnect battery ground. Discharge A/C system using
approved refrigerant recovery/recycling equipment. Disconnect A/C
hoses from expansion valve. Drain cooling system. Disconnect heater
hoses at core tubes. Disconnect blower motor wires and vent tube.
2) Remove console (if equipped). Remove lower instrument
panel. Disconnect electrical connectors at A/C relay, blower motor
resistors and A/C thermostat. Disconnect vacuum hose at vacuum motor.
Cut plastic retaining strap holding evaporator-blower housing to
heater core housing.
3) Disconnect blend-air heater control cable. Detach clip at
rear of blower housing flange and remove retaining screws. Remove