1988 JEEP CHEROKEE 6 cylinder

TORQUE SPECIFICATIONS TABLE








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Application Ft. Lbs. (N.m)
Camshaft Sprocket Bolt .......................... 80 (109)
Connecting Rod Cap Nut ........................... 33 (45)
Crankshaft Pulley-to-Damper Bolt ................. 20 (27)
Cylinder Head Bolt
4.0L
No. 11 .................................... 100 (135)
All Others ................................. 110 (149)
4.2L
No. 11 ..................................... 75 (102)
All Others .................................. 85 (115)
Exhaust Pipe-to-Manifold Bolt .................... 20 (27)
Fan & Hub Bolt ................................... 18 (24)
Flywheel-to-Crankshaft Bolt .................... 105 (142)
Fuel Rail Bolt ................................... 20 (27)
Intake & Exhaust Manifold Bolt
4.0L
Exhaust Manifold Bolts 1-5 ................... 23 (31)
Exhaust Manifold Bolts 6-7 .................. 17 (23)
Exhaust Manifold Bolts 8-11 ................. 23 (31)
Exhaust Manifold Bolts 12-13 ................ 30 (41)
4.2L ........................................... 23 (31)
Main Bearing Cap Bolt
Step 1 ......................................... 40 (54)
Step 2 ......................................... 70 (95)
Step 3 ........................................ 80 (109)
Oil Pump Attaching Bolt
Short .......................................... 10 (14)
Long ........................................... 17 (23)
Oxygen Sensor .................................... 35 (47)
Rocker Arm Bolt .................................. 19 (26)
Vibration Damper Bolt ....................... (1) 80 (109)
Water Pump Bolts ................................. 13 (18)
INCH Lbs. (N.m)
Engine Front Cover
Bolt ............................................ 60 (7)
Studs ......................................... 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) - Clean and lubricate with oil prior to tightening.









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ENGINE SPECIFICATIONS
GENERAL ENGINE SPECIFICATIONS
GENERAL SPECIFICATIONS TABLE








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Application In. (mm)
4.0L
Displacement

\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.

COMPONENT TESTING
Throttle Position Sensor
See THROTTLE POSITION SENSOR DIAGNOSTICS chart near the end
of this article. See Fig. 8.
Coolant Temperature Sensor (CTS) &
Manifold Air Temperature (MAT) Sensor
1) Disconnect the electrical connector from the sensor. Using
a high impedance, digital volt/ohmmeter, measure the resistance of the
sensor. If measured resistance is not as specified, replace sensor.
See the CTS & MAT SENSOR TEMPERATURE-TO-RESISTANCE VALUE table.
2) Test electrical harness resistance of both sensors by
testing between ECU harness connector "D-3" and sensor connector. Also
test between sensor connector and ECU harness connector "C-10" ("C-8"
on MAT sensor). Repair wire if open circuit is detected. Repair MAT
sensor wiring harness if resistance is greater than one ohm.
CTS & MAT SENSOR TEMPERATURE-TO-RESISTANCE VALUE









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F(C) Ohms
212 (100) .................................. 185
160 (71) ................................... 450
100 (38) .................................. 1600
70 (21) ................................... 3400
40 (4) .................................... 7500
20 (-7) ................................. 13,500
0 (-18) ................................. 25,000
-40 (-40) .............................. 100,700









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Manifold Absolute Pressure (MAP) Sensor
NOTE: Terminal identification letters are stamped on MAP sensor
body.
1) Disconnect electrical connector from sensor. With ignition
on and engine stopped, measure voltage output of sensor terminal "B".
See Fig. 4 . Ensure wiring harness is okay by also measuring voltage at
ECU terminal "C-t". Output voltage should be 4-6 volts at both points.
Repair or replace wiring harness as required.
2) With ignition on and engine stopped, measure supply
voltage of sensor terminal "C". See Fig. 4. Ensure wiring harness is
okay by also measuring voltage at ECU terminal "C-14". Supply voltage
should be 4.4-5.5 volts at both points. Repair or replace wiring
harness as required.
3) Using an ohmmeter, measure ground circuit resistance at
sensor terminal "A" and ECU connector terminal "D-3". Ensure wiring
harness is okay by also measuring resistance between ECU terminal "D-
3" and "B-11". If ohmmeter indicates an open circuit, check for
defective sensor ground connection at right side of cylinder block.
4) If ground connection is okay, replace ECU. If ECU terminal
"D-3" has short to 12-volts, repair wire before replacing ECU. Repair
or replace wiring harness as required.









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ABBREVIATION DEFINITION 










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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 











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"C" ABBREVIATION TABLE
"C" ABBREVIATION TABLE







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ABBREVIATION DEFINITION 










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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 

CO Carbon Monoxide 

CO2 Carbon Dioxide 

CONV Convertible 

CP Canister Purge 

CPA Connector Position Assurance 

CPS Crank Position Sensor 

CTS Coolant Temperature Sensor 

CV Check Valve or Constant Velocity 

CVC Constant Vacuum Control 

CW Clockwise 

CYL or Cyl. Cylinder 

Calif. California 

Carb. Carburetor 

Chrg. Charging 

Circ. Circuit 

Cntrl. Control 

Comp. Compressor or Compartment 

Conn. Connector 

Cont. Continued 

Conv. Convertible or Converter 

Cu. In. Cubic Inch 

Cyl. Cylinder 











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"D" ABBREVIATION TABLE
"D" ABBREVIATION TABLE







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ABBREVIATION DEFINITION 










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"D" Drive 

DBC Dual Bed Catalyst 

DC Direct Current or Discharge 

DDD Dual Diaphragm Distributor 

DERM Diagnostic Energy Reserve Module 

DFI Digital Fuel Injection 

DIC Driver Information Center 

DIS Direct Ignition System 

DIS Distributorless Ignition System 

DIST Distribution 

DISTR Distributor 

DK BLU Dark Blue 

DK GRN Dark Green 

DME Digital Motor Electronics (Motronic System) 

DOHC Double Overhead Cam 

DOT Department of Transportation 

DP Dashpot 

DRB-II Diagnostic Readout Box 

DVOM Digital Volt/Ohm Meter (see VOM) 

Def. Defogger or Defroster 

Def. Defrost 

Defog. Defogger 

Diag. Diagnostic 

Dist. Distributor or Distribution 

Dr. Door 











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"E" ABBREVIATION TABLE
"E" ABBREVIATION TABLE







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ABBREVIATION DEFINITION 

PLACING SYSTEM IN OPERATION
After component service or replacement has been completed and
all connections have been made, evacuate system throughly with a
vacuum pump. Charge system with proper amount of refrigerant and
perform a leak test. Be sure to check all fittings that have been
opened. After system has been leak tested, make a system performance
check.
SANDEN SD508 5-CYLINDER OIL CHECKING
1) Discharge system using approved refrigerant
recovery/recycling equipment. Remove compressor belt and loosen
mounting bolts. Rotate compressor in brackets until filler plug is at
top. Clean area around filler plug and remove plug slowly. Rotate
front hub plate so notch in lobe is 110 degrees from the bottom. This
rotates ball end of top piston to align with oil fill port and allows
clearance for dipstick. See Fig. 1.
2) Insert compressor dipstick diagonally from right to left
until stop on dipstick contacts filler plug surface. Remove dipstick
and note oil fill level. Each mark on dipstick represents one ounce
of oil. Add oil if necessary to reach 3-4 ounce level.
Fig. 1: Sanden 5-Cylinder Oil Level Checking
YORK - 2-CYLINDER - PURGINE COMPRESSOR

1) Remove gauge set and place caps on service valve ports.
Back-seat the suction service valve to allow refrigerant to enter
compressor.
2) Loosen discharge port valve slightly. Loosen valve port
cap to allow refrigerant to force out air from compressor. Back-seat
the discharge valve and tighten the port cap. Compressor is ready for
service.
YORK - 2-CYLINDER COMPRESSOR OIL CHECKING
1) Operate system for 10 minutes, then stop and isolate
compressor. Loosen filler plug slowly to release any pressure in
crankcase.
2) Use dipstick to check oil level. See Fig. 2. Add oil as
necessary, then install plug with new "O" ring. Purge compressor of
air.
Fig. 2: York A/C Compressor Oil Level Dipstick (Check oil w/ shaft
keyway facing head)
Courtesy of Chrysler Motors.

2) Loosen discharge port valve slightly. Loosen valve port
cap to allow refrigerant to force out air from compressor. Back-seat
the discharge valve and tighten the port cap. Compressor is ready for
service.
REFRIGERATION OIL
Only new, pure, moisture-free refrigeration oil should be
used in the air conditioning system. This oil is highly refined and
dehydrated (moisture content less than 10 parts per million).
Refrigeration oil container must be kept tightly closed at
all times when not in use, or moisture will be absorbed from the air
and introduced into the refrigeration system.
NIPPONDENSO 10-CYLINDER
SHAFT SEAL
NOTE: Check compressor refrigerant oil level when replacing seals.
See COMPRESSOR REFRIGERANT OIL CHECKING article in this
section.
Removal
1) Hold clutch hub stationary and remove center nut. Screw
remover into center of hub. Turn center bolt to remove pressure plate.
2) Remove shims from shaft. Remove snap ring from inside of
pulley. Tap pulley off of shaft with plastic mallet. Be careful not
to distort pulley while removing.
3) Disconnect clutch coil wires from compressor housing.
Remove snap ring inside coil and lift coil off compressor. Pry dust
seal out from around compressor shaft (if equipped).
4) Place shaft key remover on shaft and turn to remove key.
Remove drain plug (if equipped). Remove bolts holding service valves
to body of compressor and remove valves. Discard "O" rings. Drain oil
out of compressor.
5) Remove 6 through bolts from front head of compressor and
discard washers. Tap head loose from compressor, being careful not to
scratch sealing surfaces. Remove snap ring (if equipped) from front
housing. Press seal plate out. Remove seal from shaft. See Fig. 1.
Installation
1) Lubricate shaft seal with clean refrigerant oil. Place on
compressor shaft. Lubricate seal plate (and "O" ring, if equipped) and\
install in front housing. Install snap ring (if equipped).
2) Place front housing on compressor body. Using new
washers, install through bolts. Tighten bolts evenly and alternately
to 18 ft. lbs. (24 N.m). Install shaft key with installer and plastic
mallet. Insert dust seal into front of compressor.
3) Install drain plug using new gasket. Add correct amount
of refrigerant oil to compressor. If service valves were removed,
coat new "O" rings with refrigerant oil and install service valves.
4) Place clutch coil on compressor and install snap ring.
Install shims on shaft to adjust clearance between pressure plate and
rotor to .016-.028" (.41-.71 mm). Tighten shaft nut to 12 ft. lbs. (1\
6
N.m). See REFRIGERANT OIL & R-12 SPECIFICATIONS table for system
capacities.
SANKYO/SANDEN 5-CYLINDER COMPRESSOR SERVICING
NOTE: During the past year, Sankyo International (USA), Inc. has
changed its name to Sanden International (USA), Inc.