ESP JEEP CHEROKEE 1988 Service User Guide

IGNITION SWITCHES
INDICATOR LIGHTS
KEYLESS ENTRY KEYPADS AND TRANSMITTERS
KEYLESS ENTRY TRANSMITTERS
LEDS
LENSES
MICROPHONES
MIRRORS (ELECTROCHROMATIC AND HEATED)
MOTORS
NEUTRAL SAFETY SWITCHES
ODOMETERS
ODOMETERS, SPEEDOMETERS AND TACHOMETERS (CABLE-DRIVEN)
PULLEYS
RECEIVERS, AMPLIFIERS, EQUALIZERS AND SUB-WOOFER VOLUME CONTROLS
RELAY BOXES
RELAYS
SEALED BEAMS
SEAT HEATERS
SECURITY ALARM SENSORS
SIRENS
SOLENOIDS
SPEAKERS AND MICROPHONES
SPEEDOMETER AND TACHOMETER LINKAGES AND CABLES
SPEEDOMETER CABLES
SPEEDOMETERS
STARTERS
SUB-WOOFER VOLUME CONTROLS
SWITCHES
TACHOMETER CABLES
TACHOMETERS
TAPE PLAYERS AND CD PLAYERS
TENSIONERS
TIMERS
TIRE PRESSURE SENSORS
TRANSCEIVERS
TRANSDUCERS
VACUUM ACCUMULATORS (RESERVOIRS)
VACUUM RESERVOIRS
VOLTAGE REGULATORS
WASHER FLUID LEVEL SENDERS
WASHER PUMPS
WIPER ARMS AND BLADES
WIPER BLADES
WIPER HOSES AND NOZZLES
WIPER LINKAGES
WIPER NOZZLES
WIPER PUMP RESERVOIRS
WIRING HARNESSES AND CONNECTORS
INTRODUCTION TO MOTORIST ASSURANCE PROGRAM (MAP)
OVERVIEW OF MOTORIST ASSURANCE PROGRAM
The Motorist Assurance Program is the consumer outreach
effort of the Automotive Maintenance and Repair Association, Inc.
(AMRA). Participation in the Motorist Assurance Program is drawn from
retailers, suppliers, independent repair facilities, vehicle
manufacturers and industry associations.
Our organization's mission is to strengthen the relationship
between the consumer and the auto repair industry. We produce
materials that give motorists the information and encouragement to
take greater responsibility for their vehicles-through proper,

EM IS SIO NS S TA N DAR DS

1988 J e ep C hero ke e
1988 EMISSION & TUNE-UP STANDARDS
MANUFACTURING STANDARDS
Federal and state governments have established air quality
standard during the past 20 years. Automobile manufacturers design
their vehicles to conform to standards where the vehicle will be sold
and operated. These standards cover carbon monoxide (CO), hydrocarbons\
(HC) and oxides of nitrogen (NOx).
Federal and California Standards which must be met by
manufacturers are specified in units easily measured in a testing
laboratory. Since 1970, these standards have been in "grams per mile".
This means no vehicle, whether 2-cylinder or V8, may emit more than a
set weight (in grams) of pollutants for each mile travelled. Since
large engines burn more fuel per mile than do small engines, they must
be "cleaner" per gallon burned if they are to meet these standards.
When manufacturers certify vehicle models prior to sale,
the vehicles are placed on a dynamometer and the exhaust gases are
collected in a bag. After the vehicle runs for a specified time, the
gases are analyzed and weighed. Engines and emission systems are
designed so the weight of emissions will be less than the specified
grams per mile standard.
Infra-red exhaust analyzers are commonly used in vehicle test
stations. The analyzer uses a test probe placed in the exhaust stream
to sample the exhaust gases, and measure the percentage of CO and the
parts per million of HC. These are not the same units used by the
manufacturer when the vehicle is certified. The NOx emissions cannot
be measured by an infra-red exhaust analyzer. Laboratory equipment
must be used to determine NOx emissions.
TUNE-UP STANDARDS
The technician must use the proper specifications when
adjusting the vehicle during a tune-up. The first few years of
emission-regulated vehicles were adjusted using an exhaust gas
analyzer which measured CO and HC.
In the past few years, manufacturers have produced much
cleaner running vehicles. The CO (percentage) and HC (ppm) have beco\
me
very low, especially when measured downstream of catalytic converter.
It has become difficult to measure the effect of fuel and ignition
adjustments.
One solution to this problem for vehicles using carburetors
requires the use of artificially-enriched propane adjustments. The
added propane increases or decreases engine RPM for evaluation of
carburetor rich/lean setting. This allows the technician to check
carburetor setting quickly and accurately.
As computer-controlled systems were developed, it became
possible for the vehicles to adjust the air/fuel ratio, ignition
timing and emission control device operation throughout the entire
driving range. These computer control systems use a variety of sensors
that provide the electronic control unit with information on vehicle
speed, altitude of vehicle operation and transmission gear position,
along with engine operating conditions.
Fuel delivery to achieve a lean air/fuel ratio is controlled
by the computer. The computer controls the on/off (duty cycle) time of\
the fuel injector(s) or carburetor mixture control solenoid to achieve\
leanest possible air/fuel ratio while maintaining good driveability.
Although most repair shops have exhaust gas analyzers,
computer-controlled vehicles normally do not have a CO and HC

NOTE: Always refer to appropriate engine overhaul article in the
ENGINES section for complete overhaul procedures and
specifications for the vehicle being repaired.
REMOVAL
Remove intake and exhaust manifolds and valve cover. Cylinder
head and camshaft carrier bolts (if equipped), should be removed only
when the engine is cold. On many aluminum cylinder heads, removal
while hot will cause cylinder head warpage. Mark rocker arm or
overhead cam components for location.
Remove rocker arm components or overhead cam components.
Components must be installed in original location. Individual design
rocker arms may utilize shafts, ball-type pedestal mounts or no rocker
arms. For all design types, wire components together and identify
according to the corresponding valve. Remove cylinder head bolts.
Note length and location. Some applications require cylinder head
bolts be removed in proper sequence to prevent cylinder head damage.
See Fig. 1 . Remove cylinder head.
Fig. 1: Typical Cylinder Head Tightening or Loosening Sequence
This Graphic For General Information Only
INSTALLATION
Ensure all surfaces and head bolts are clean. Check that head
bolt holes of cylinder block are clean and dry to prevent block damage
when bolts are tightened. Clean threads with tap to ensure accurate
bolt torque.
Install head gasket on cylinder block. Some manufacturer's
may recommend sealant be applied to head gasket prior to installation.
Note that all holes are aligned. Some gasket applications may be
marked so certain area faces upward. Install cylinder head using care
not to damage head gasket. Ensure cylinder head is fully seated on
cylinder block.
Some applications require head bolts be coated with sealant
prior to installation. This is done if head bolts are exposed to water
passages. Some applications require head bolts be coated with light
coat of engine oil.

Ensure cylinder is checked for taper, out-of-round and
properly honed prior to checking piston and cylinder bore fit. See
CYLINDER BLOCK in this article. Using dial bore gauge, measure
cylinder bore. Measure piston at right angle to piston pin in center
of piston skirt area. Subtract piston diameter from cylinder bore
diameter. The difference is piston-to-cylinder clearance. Clearance
must be within specification. Mark piston for proper cylinder
location.
ASSEMBLING PISTON & CONNECTING ROD
Install proper fitted piston on connecting rod for proper
cylinder. Ensure piston marking on top of piston marked is in
correspondence with connecting rod and cap number. See Fig. 14.
Fig. 14: Piston Pin Installation - Typical
This Graphic For General Information Only
Lubricate piston pin and install in connecting rod. Ensure
piston pin retainers are fully seated (if equipped). On pressed type
piston pins, follow manufacturer's recommended procedure to avoid
distortion or breakage.
CHECKING PISTON RING CLEARANCES

Fig. 19: Measuring Bearing Clearance - Typical
This Graphic For General Information Only
Micrometer & Telescopic Gauge Method
A micrometer is used to determine journal diameter, taper and
out-of-round dimensions of the crankshaft. See CLEANING & INSPECTION
under CRANKSHAFT & MAIN BEARINGS in this article.
With crankshaft removed, install bearings and caps in
original location on cylinder block. Tighten bolts to specification.
On connecting rods, install bearings and caps on connecting rods.
Install proper connecting rod cap on corresponding rod. Ensure bearing
cap is installed in original location. Tighten bolts to specification.
Using a telescopic gauge and micrometer or inside micrometer
measure inside diameter of connecting rod and main bearings bores.
Subtract each crankshaft journal diameter from the corresponding
inside bore diameter. This is the bearing clearance.

SUPER CHARGERS
SWITCHES
THERMAL VACUUM VALVES
THERMOSTATIC AIR DOOR ASSEMBLIES
THERMOSTATS AND HOUSINGS
THROTTLE BODIES
THROTTLE CABLES
THROTTLE LINKAGES AND CABLES
THROTTLE POSITION SENSORS
THROTTLE POSITION SWITCHES
TIMING BELT SPROCKETS
TIMING BELTS
TORQUE STRUTS
TRANSMISSION RANGE SWITCHES
TUBE CLAMPS
TUBE CONNECTORS
TUBE COUPLERS
TUBES
TURBO CHARGERS
VACUUM CONNECTIONS
VACUUM HOSES, TUBES AND CONNECTIONS (NON-METALLIC)
VACUUM REGULATOR SOLENOIDS
VACUUM TUBES
VEHICLE SPEED SENSORS
VOLUME AIR FLOW SENSORS
WASTE GATE CONTROL SOLENOIDS
WASTE GATES AND BOOST CONTROL MECHANISMS
WATER PUMPS (ELECTRIC)
WATER PUMPS (NON-ELECTRIC)
WIRING HARNESSES AND CONNECTORS
INTRODUCTION TO MOTORIST ASSURANCE PROGRAM (MAP)
OVERVIEW OF MOTORIST ASSURANCE PROGRAM
The Motorist Assurance Program is the consumer outreach
effort of the Automotive Maintenance and Repair Association, Inc.
(AMRA). Participation in the Motorist Assurance Program is drawn from
retailers, suppliers, independent repair facilities, vehicle
manufacturers and industry associations.
Our organization's mission is to strengthen the relationship
between the consumer and the auto repair industry. We produce
materials that give motorists the information and encouragement to
take greater responsibility for their vehicles-through proper,
manufacturer-recommended, maintenance. We encourage participating
service and repair shops (including franchisees and dealers) to adopt
(1) a Pledge of Assurance to their Customers and (2) the Motorist
Assurance Program Standards of Service. All participating service
providers have agreed to subscribe to this Pledge and to adhere to the
promulgated Standards of Service demonstrating to their customers that
they are serious about customer satisfaction.
These Standards of Service require that an inspection of the
vehicle's (problem) system be made and the results communicated to the\
customer according to industry standards. Given that the industry did
not have such standards, the Motorist Assurance Program successfully
promulgated industry inspection communication standards in 1994-95 for
the following systems: Exhaust, Brakes, ABS, Steering and Suspension,
Engine Maintenance and Performance, HVAC, and Electrical Systems.
Further, revisions to all of these inspection communication standards
are continually re-published. In addition to these, standards for
Drive Train and Transmissions have recently been promulgated.
Participating shops utilize these Uniform Inspection & Communication

\003
* E XH AU ST S YSTE M U NIF O RM IN SPEC TIO N G UID ELIN ES *

1 988 J e ep C hero ke e
GENERAL INFORMATION
Exhaust Systems Motorist Assurance Program
Standards For Automotive Repair
All Makes and Models
INTRODUCTION TO MOTORIST ASSURANCE PROGRAM (MAP)
CONTENTS
Motorist Assurance Program (MAP)
OVERVIEW OF MOTORIST ASSURANCE PROGRAM
OVERVIEW OF SERVICE REQUIREMENTS AND SUGGESTIONS
Exhaust
CATALYTIC CONVERTERS
EXHAUST AND TAIL PIPES
EXHAUST CONNECTIONS
HANGERS
HEAT RISERS (MECHANICAL EFE DEVICES)
HEAT SHIELDS
MANIFOLDS (CAST AND TUBE TYPE)
MECHANICAL EFE DEVICES
MUFFLERS AND RESONATORS
INTRODUCTION TO MOTORIST ASSURANCE PROGRAM (MAP)
OVERVIEW OF MOTORIST ASSURANCE PROGRAM
The Motorist Assurance Program is the consumer outreach
effort of the Automotive Maintenance and Repair Association, Inc.
(AMRA). Participation in the Motorist Assurance Program is drawn from
retailers, suppliers, independent repair facilities, vehicle
manufacturers and industry associations.
Our organization's mission is to strengthen the relationship
between the consumer and the auto repair industry. We produce
materials that give motorists the information and encouragement to
take greater responsibility for their vehicles-through proper,
manufacturer-recommended, maintenance. We encourage participating
service and repair shops (including franchisees and dealers) to adopt
(1) a Pledge of Assurance to their Customers and (2) the Motorist
Assurance Program Standards of Service. All participating service
providers have agreed to subscribe to this Pledge and to adhere to the
promulgated Standards of Service demonstrating to their customers that
they are serious about customer satisfaction.
These Standards of Service require that an inspection of the
vehicle's (problem) system be made and the results communicated to the\
customer according to industry standards. Given that the industry did
not have such standards, the Motorist Assurance Program successfully
promulgated industry inspection communication standards in 1994-95 for
the following systems: Exhaust, Brakes, ABS, Steering and Suspension,
Engine Maintenance and Performance, HVAC, and Electrical Systems.
Further, revisions to all of these inspection communication standards
are continually re-published. In addition to these, standards for
Drive Train and Transmissions have recently been promulgated.
Participating shops utilize these Uniform Inspection & Communication

ECU is a digital microprocessor computer. Data sensors
provide the ECU with engine operating information in varying
electrical signals. ECU calculates this information and corrects
air/fuel ratio, ignition timing, and emission control as needed to
maintain efficient engine operation. Other ECU output signals control
upshift indicator light (manual transmission only), ignition module
dwell and A/C clutch operation.
UPSHIFT INDICATOR
On vehicles equipped with a manual transmission, ECU
controls upshift indicator light. Indicator light is normally
illuminated when ignition is turned on without engine running.
Indicator light is turned off when engine is started.
Indicator light will be illuminated during engine operation
in response to engine load and speed. If transmission is not shifted,
ECU will turn light off after 3 to 5 seconds. A switch located on
transmission prevents indicator light from being illuminated when
transmission is shifted to highest gear.
DATA SENSORS & SWITCHES
Manifold Absolute Pressure (MAP) Sensor
MAP sensor is located in engine compartment on firewall,
behind engine. MAP sensor monitors manifold vacuum via a vacuum line
from intake manifold to sensor.
MAP sensor supplies an electrical signal which keeps ECU
informed of manifold vacuum and barometric pressure conditions. This
information is combined with data supplied by other sensors to
determine correct air/fuel ratio.
Oxygen Sensor
Oxygen (O2) sensor is mounted in exhaust manifold where it
is exposed to exhaust gas flow. Its function is to monitor oxygen
content of exhaust gases and to supply ECU with a voltage signal
directly proportional to this content.
If oxygen content of exhaust gases is high (lean air/fuel
mixture), voltage signal to ECU is low. As oxygen content decreases
(mixture becomes richer), signal voltage increases.
In this way, ECU is kept constantly informed of air/fuel
ratio. ECU can then alter fuel injector "on" time, in response to
these signals, to obtain best air/fuel ratio of 14.7:1 under any
given operating conditions.
O2 sensor is equipped with a heating element that keeps
sensor at proper operating temperatures. Maintaining correct sensor
temperatures at all times guarantees a more accurate signal to ECU.
By using an O2 heater, fuel control system may also enter "closed
loop" operating mode sooner and maintain this mode, even during
periods of extended idle.
Temperature Sensors
There are 2 temperature sensors used on this system.
Manifold Air Temperature (MAT) sensor, mounted in intake manifold,
measures temperature of incoming air/fuel mixture and Coolant
Temperature Sensor (CTS), located on left side of cylinder block just
below the exhaust manifold, measures temperature of engine coolant.
Information provided by these 2 sensors to ECU allows ECU to
demand slightly richer air/fuel mixtures and higher idle speeds
during cold engine operation.
Throttle Position Sensor (TPS)
TPS is regulated by movement of throttle shaft. It is

Coolant temperature sensor is installed in intake manifold
water jacket to provide coolant temperature input signal for ECU.
During cold engine operation, ECU will make mixture richer, make up
for fuel condensation in cold intake manifold, increase idle speed
during warm-up period, increase ignition advance and keep EGR system
inoperative until engine warms up.
THROTTLE POSITION SENSOR (TPS)
Throttle position sensor provides ECU with input signal, up
to about 5 volts, to indicate throttle position. This allows ECU to
control air/fuel mixture according to throttle position. TPS is
mounted on throttle body assembly.
WIDE OPEN THROTTLE (WOT) SWITCH
WOT switch provides an input signal to ECU when engine is at
wide open throttle. The ECU enriches air/fuel mixture. The WOT switch
is located on the side of throttle body.
CLOSED THROTTLE (IDLE) SWITCH
Idle switch is integral with ISA motor and provides voltage
signal to ECU. ECU will signal ISA motor to change throttle stop
angle in response to engine operating conditions.
UPSHIFT INDICATOR LIGHT
On vehicles equipped with a manual transmission, ECU
controls upshift indicator light. Indicator light is normally
illuminated when ignition is turned on without engine running.
Indicator light is turned off when engine is started.
Indicator light will be illuminated during engine operation
in response to engine load and speed. If transmission is not shifted,
ECU will turn light off after 3 to 5 seconds. A switch located on
transmission prevents indicator light from being illuminated when
transmission is shifted to highest gear.
ENGINE SPEED SENSOR
Engine speed sensor is attached to bellhousing. It senses
and counts teeth on flywheel gear ring as they pass during engine
operation. Signal from speed sensor provides ECU with engine speed
and crankshaft angle. On flywheel gear ring, large trigger tooth and
notch is located 90 degrees before each TDC point. Each trigger tooth
is followed by 12 smaller teeth and notches before TDC point is
reached.
As each of 12 small teeth and notches pass magnetic core in
speed sensor, concentration and collapse of magnetic field induces
slight voltage (spike) in sensor pick-up coil winding. See Fig. 2.
Larger trigger teeth and notches induce higher voltage (spike) in
sensor pick-up coil winding. These voltage spikes enable ECU to count
teeth as they pass speed sensor.
Higher voltage spike (from larger tooth and notch) indicates
to ECU that piston will be at TDC position after 12 smaller voltage
spikes have been counted. ECU will then either advance or retard
ignition timing depending upon remaining sensor inputs.

position. The engine speed sensor senses TDC, BDC, and engine speed by
detecting the flywheel teeth as they pass by the sensor during engine
operation. The engine speed sensor is non-adjustable.
The flywheel has three trigger notches, 120
apart. See
Fig. 7 . There are 20 small teeth between each trigger notch. Each
large trigger notch is located 12 small teeth before each Top Dead
Center (TDC) position of the corresponding pistons.
Fig. 7: Location of Engine Speed Sensor
Courtesy of Chrysler Motors.
When a small tooth and notch pass the magnet core in the
sensor, the concentration, followed by the collapse of the magnetic