1988 JEEP CHEROKEE check engine
[x] Cancel search: check enginePage 82 of 1378
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.
Page 84 of 1378
ELECTRONIC CONTROL UNIT (ECU)
Removal & Installation
Information not available from manufacturer.
COOLANT TEMPERATURE SENSOR (CTS)
Removal & Installation
Drain cooling system. Remove air cleaner assembly. Disconnect
electrical connector and remove sensor from block. To install, reverse
removal procedure. Refill cooling system.
OXYGEN (O2) SENSOR
Removal & Installation
Raise and support vehicle. Disconnect electrical connector
from sensor. Remove sensor from exhaust manifold. Install and tighten
sensor to 35 ft. lbs. (47 N.m). Reconnect electrical connector. Lower
vehicle.
THROTTLE POSITION SENSOR (TPS)
Removal
Disconnect electrical connector from TPS. Bend lock tabs away
from retaining screws and remove screws. Remove TPS.
Installation
With throttle valve in normal closed position, install TPS.
Install TPS retaining screws. Perform OUTPUT CHECK.
NOTE: Throttle position sensor is nonadjustable. Only output
voltage can be monitored.
Output Check (Manual Transmission Only)
1) Connect negative lead of digital voltmeter to terminal "B"
and positive lead to terminal "A" of TPS connector. Do not disconnect
electrical connector. Insert leads through back of connector. It may
be necessary to remove throttle body from vehicle to gain access to
connector.
2) Turn ignition on, engine off. With throttle closed and
resting against idle stop, input voltage should be about 5 volts. Move
positive lead from terminal "B" to terminal "C" and read voltage
output. Output voltage should be about 0.8 volt with throttle closed
and resting against idle stop.
3) If voltage is not as specified, loosen lower retaining
screw and pivot sensor for large adjustments. Loosen upper retaining
screw and pivot sensor for small adjustments. Adjust sensor so output
voltage reading equals 16 percent of input voltage. If voltage
specifications cannot be obtained, replace sensor. Remove voltmeter.
Tighten screws and bend retaining tabs into position.
ALL OTHER SENSORS, SOLENOIDS & SWITCHES
Removal & Installation
Removal of sensors, switches, and solenoids is accomplished
by disconnecting the electrical and/or vacuum connectors and removing
or detaching the component. To install, reverse removal procedure.
TESTING
NOTE: Refer to Figs. 8-10 for Testing information.
Page 101 of 1378
\003
A/C C O M PR ESSO R O IL C HEC KIN G
1988 J e ep C hero ke e
A/C General Servicing
COMPRESSOR OIL CHECK
* PLEASE READ THIS FIRST *
CAUTION: When discharging air conditioning system, use only approved
refrigerant recovery/recycling equipment. Make every attempt
to avoid discharging refrigerant into the atmosphere.
ISOLATING COMPRESSOR - GRAND WAGONEER ONLY
1) Connect service gauge set to the compressor service valves
and open compressor valves slightly (turn clockwise). Start engine and\
operate air conditioning. Slowly turn compressor suction valve
clockwise toward closed (front-seated) position.
2) When suction pressure is reduced to zero or less, turn off
engine and compressor and quickly turn suction valve stem in to full
front-seated position. Suction pressure should be slightly above zero.
Turn discharge valve into front-seated position.
3) To check oil lever, slowly open crankcase plug to relieve
any remaining pressure. After oil level is correct, cap service gauge
parts on both valves. Back-seat suction service valve to allow
refrigerant to enter compressor. Open discharge valve halfway.
4) Loosen discharge service valve cap, allowing refrigerant
pressure to force air out of compressor. Back-seat service valve and
tighten cap. Compressor is now ready for operation.
REFRIGERANT OIL
Only new, pure, moisture-free refrigerant oil should be used
in the air conditioning system. This oil is highly refined and
dehydrated to a point where moisture content is less than 10 parts per
million. The oil container must be tightly closed at all times when
not in use, or moisture will be absorbed from the air and introduced
into the refrigeration system.
DISCHARGING SYSTEM
CAUTION: When discharging air conditioning system, use only approved
refrigerant recovery/recycling equipment. Make every attempt
to avoid discharging refrigerant into the atmosphere.
If compressor has stem-type service valves, it can be
isolated and removed without discharging entire system. Otherwise,
discharge system completely using approved refrigerant
recovery/recycling equipment before loosening any fittings.
DISCONNECTING LINES & FITTINGS
After system is discharged, carefully clean area around all
fittings to be opened. Always use 2 wrenches when tightening or
loosening fittings to avoid twisting or distorting lines. Cap or plug
all openings as soon as lines are removed. Do not remove caps until
immediately before connections are made. This will keep entry of air
and moisture to a minimum, reducing the chance of damage to
components.
Page 105 of 1378
of the scale, a symbol for defroster indicates defrost position. In
"BI-LEVEL" position, a mixture of floor heat and defroster air is
obtained.
The lower temperature control lever operates blend-air door
in heater core housing. At full right position, all air is directed
through heater core, providing maximum heat flow. At full left
position, all air is directed around heater core providing fresh air.
Control can be set in any intermediate position to provide a blend of
heated and unheated air. Heater must be in heat or defrost mode before
any air can enter vehicle.
TROUBLE SHOOTING
See JEEP TROUBLE SHOOTING at the end of this article.
REMOVAL & INSTALLATION
CONDENSER
Removal (Cherokee, Comanche & Wagoneer) NOTE: On these
models, condenser and receiver-drier are replaced
as a unit.
1) Drain radiator. Disconnect fan shroud and radiator hoses.
Disconnect automatic transmission cooler lines (if equipped).
Discharge A/C system using approved refrigerant recovery/recycling
equipment.
2) Disconnect A/C hoses from condenser. Unplug low pressure
switch. Remove radiator and condenser as an assembly. Detach condenser
retaining bolts. Separate condenser from radiator. Remove receiver-
drier from condenser.
NOTE: Plug receiver-drier openings whenever unit is removed from
condenser. Add 1 oz. of refrigerant oil (AMC No. 8132400) to
system when replacing condenser.
Installation
To install, reverse removal procedure. Fill radiator.
Evacuate, leak test, recharge and check A/C system operation.
Removal (Wrangler)
1) Discharge system (slowly to prevent loss of compressor
oil) using approved refrigerant recovery/recycling equipment. Drain
coolant. Remove fan shroud and radiator. Disconnect pressure line at
condenser. Remove condenser mounting screws. Tilt bottom of condenser
toward engine.
2) From underside of vehicle, disconnect hose attaching
receiver-drier to evaporator. Plug all openings to prevent entry of
dirt or moisture. Remove receiver-drier and condenser assembly. Remove
receiver-drier from condenser.
Installation
To install, reverse removal procedure. Fill radiator.
Evacuate, leak test, recharge and check A/C system operation.
RECEIVER-DRIER
NOTE: On Cherokee, Comanche and Wagoneer, receiver-drier is
removed with condenser and radiator as an assembly.
Removal (Wrangler)
Page 107 of 1378
housing attaching nuts from studs on engine compartment side of dash
panel. Remove evaporator drain tube.
4) Remove right kick panel. Detach instrument panel support
bolt. Gently pull on right side of dash, then rotate housing downward
and toward rear of vehicle to disengage housing studs from dash panel.
Remove evaporator-blower housing.
5) To remove heater core, detach retaining screws. Remove
heater core by pulling straight out of housing. To remove evaporator
core, detach top housing retaining screws, then remove top of
evaporator housing.
6) Remove thermostatic switch and capillary tube. Detach 2
evaporator retaining screws and lift evaporator core from housing.
Remove expansion valve from evaporator.
Installation
1) To install components, reverse removal procedure. When
installing evaporator core, install thermostatic switch and capillary
tube before installing top of housing.
2) When installing heater core, ensure seal is properly
cemented in place to prevent it from moving when blower assembly is
installed. Evacuate, leak test, recharge and check A/C system
operation.
NOTE: The evaporator housing mounting location is similar to
Wrangler, except blower motor is mounted horizontally to
firewall.
Removal (Wrangler)
1) Discharge system using approved refrigerant
recovery/recycling equipment. Disconnect inlet line at compressor.
Disconnect hose, at quick-disconnect coupling, between receiver-drier
and evaporator. Remove hose clamps and dash grommet retaining screws.
See Fig. 2 .
Fig. 2: Wrangler Evaporator Housing Mounting Screw Locations
Courtesy of Chrysler Motors.
NOTE: It is not necessary to discharge system to service blower
motor. Evaporator housing may be lowered from instrument
Page 115 of 1378
System Charge Test
1) To check system refrigerant level, a sight glass has been
incorporated into the receiver-to-evaporator hose at the receiver end.
A continuous stream of bubbles will appear in the sight glass of a
system that is not properly charged. However, both properly charged
systems and discharged systems will appear the same because of a lack
of bubbles.
2) To test for discharge condition, cycle the clutch off and
on with engine at 1500 RPM. When clutch is off, bubbles will appear if
there is refrigerant in the system. If no bubbles appear, system is
discharged. If discharged, leak test, repair and recharge system.
A/C SYSTEM OPERATION CHART & VACUUM DIAGRAM
A/C SYSTEM OPERATION TABLE \
\
\
\
\
\
\
MODE
LEVER BLOWER PANEL FLOOR DEFROST WATER
POSITION AIR DISCHARGE SPEEDS DOOR DOOR DOOR VALVE
\
\f\
\f\
\f\
\f\
\f\
\f\
Off(
1)( 2) Closed None Open ( 3) Closed Closed
\
\f\
\f\
\f\
\f\
\f\
\f\
Max A/C Panel Regis- 4
(
1)( 4) ters With Open Bleed Closed Open( 5)
Floor Bleed
\
\f\
\f\
\f\
\f\
\f\
\f\
Norm A/C Panel Regis- 4(
6) Open Bleed Closed Open( 5)
(
7)( 4) ters With
Floor Bleed
\
\f\
\f\
\f\
\f\
\f\
\f\
Bi-Level Panel 4(
6) Open Open Bleed Open( 1)
(
7)( 4) Registers
and Floor
With Def.
Bleed
\
\f\
\f\
\f\
\f\
\f\
\f\
Vent Panel 4 Open Bleed Closed Closed
(
7)( 2) Registers
With Floor
Bleed
\
\f\
\f\
\f\
\f\
\f\
\f\
Heat Floor With 4 Closed Open Bleed Open(
1)
(
7)( 2) Def. Bleed
\
\f\
\f\
\f\
\f\
\f\
\f\
Def. Defroster 4 Closed Bleed Open Open(
1)
(
7)( 2) With Floor
Bleed
\
\
\
\
\
\
\
(
1) - Recirculating Door is in Recirc. position.
(
2) - Indeterminate
(
3) - A/C Compressor is OFF
(
4) - A/C Compressor is ON
(
5) - Water valve closes in full "COOL" temperature lever position.
(
6) - Speeds are reduced by approximately 2.0 Volts.
(
7) - Recirculating Door is in Outside position.
\
\
\
\
\
\
\
\b
Page 136 of 1378
Threads damaged ......... A .. Require repair or replacement.
Threads stripped (threads
missing) ............... A ............ Require replacement.
Wire lead conductors
exposed ................ B .. Require repair or replacement.
Wire lead corroded ...... A .. Require repair or replacement.
Wire lead open .......... A .. Require repair or replacement.
Wire lead shorted ....... A .. Require repair or replacement.
(1) - Refer to manufacturer's diagnostic trouble code
procedure and require repair or replacement of
affected component(s).
( 2) - Determine cause and correct prior to repair or
replacement of part.
( 3) - Determine source of contamination, such as engine coolant,
fuel, metal particles, or water. Require repair or
replacement. Check for accepted cleaning procedure.
( 4) - Inoperative includes intermittent operation or out of
OEM specification. Some components may be serviceable.
\
\
\
\
\
\
\
COOLANT
COOLANT INSPECTION \
\
\
\
\
\
\
Condition Code Procedure
Acidity (pH) incorrect .. 1 ........... Suggest correction or
replacement.
Contaminated ............ B ...... ( 1) Require replacement or
recycling. Further
inspection required.
Level incorrect ......... B .......... ( 2) Require filling to
proper level.
Maintenance intervals ... 3 ........ ( 3) Suggest replacement.
Mixture incorrect ....... B ........... Require correction or
replacement.
Type incorrect .......... B ............ Require replacement.
( 1) - Determine source of contamination and require correction
prior to coolant replacement.
( 2) - Determine source of incorrect level and suggest repair.
( 3) - The system should be drained and/or flushed and
refilled with correct coolant according to OEM
recommended service interval and procedures.
\
\
\
\
\
\
\
COOLING FAN BLADES
COOLING FAN BLADE INSPECTION \
\
\
\
\
\
\
Condition Code Procedure
Application incorrect ... B ............ Require replacement.
Attaching hardware
broken ................. A ... Require repair or replacement
of hardware.
Attaching hardware
missing ................ C .......... Require replacement of
hardware.
Attaching hardware not
functioning ............ A ... Require repair or replacement
of hardware.
Page 157 of 1378
\003
A/C S YSTE M D IA G NO SIS
1988 J e ep C hero ke e
1988 AIR CONDITIONING & HEAT
A/C General Servicing
Diagnostic Procedures
Jeep; All Models
DIAGNOSTIC PROCEDURES
Diagnosis is an important first step in A/C system servicing.
To save time and effort, systems should be carefully checked to
identify the causes of poor performance. By using the following
diagnostic charts, defective components or system damage can be
quickly located. To identify problems that are specific to one system,
refer to the repair section of this manual. The charts in this section
apply to all systems.
PREPARATION FOR TESTING
1) Attach Low and High side gauges.
2) Start engine and allow it to warm up.
3) Set system to COOL and blower to HIGH.
4) Open car doors and hood.
5) Run at fast idle for 2-3 minutes.
ALTITUDE PRESSURE VARIATIONS TABLE
ALTITUDE PRESSURE VARIATIONS TABLE \
\
\
\
\
\
\
Altitude Absolute Gauge Altitude
(Ft.Above Pressure Of Correction
Sea Level) Atmosphere (psi) (1) (psi)
0 .......................... 14.7 .............................. 0
1000 ....................... 14.2 ............................ 0.5
2000 ....................... 13.7 ............................ 1.0
3000 ....................... 13.2 ............................ 1.5
4000 ....................... 12.7 ............................ 2.0
5000 ....................... 12.2 ............................ 2.5
6000 ....................... 11.7 ............................ 3.0
7000 ....................... 11.3 ............................ 3.4
8000 ....................... 10.9 ............................ 3.8
9000 ....................... 10.5 ............................ 4.2
10,000 ..................... 10.1 ............................ 4.6
( 1) - Add correction shown from gauge readings
\
\
\
\
\
\
\
ALTITUDE VACUUM VARIATIONS TABLE
ALTITUDE VACUUM VARIATIONS TABLE \
\
\
\
\
\
\
Altitude Complete Gauge Altitude
(Ft.Above Vacuum Correction
Sea Level) (In. Hg) (1) (In. Hg)
0 .......................... 29.92 ............................. 0
1000 ....................... 28.92 ........................... 1.0