check engine MITSUBISHI MONTERO 1991 Service Manual

intake hoses and EGR pipe. Disconnect oxygen sensor electrical
connector.
2) Remove oil pipe and EGR valve. Disconnect exhaust fitting
and remove rear heat protector. Remove oil return pipe. Remove
turbocharger assembly. See Fig. 11.
Fig. 11: Removing Rear Turbocharger (Stealth & 3000GT)
Courtesy of Mitsubishi Motor Sales of America.
Inspection
Check turbine and compressor wheels for cracking and other
damage. Make sure turbine and compressor wheels turn smoothly. Check
for oil leakage from turbocharger assembly. Check for proper wastegate
valve operation. See SYSTEM & COMPONENT TESTING article.
Installation
1) To install, reverse removal procedure. Before oil pipe
flare nut (above turbocharger) is installed, pour clean engine oil
into turbocharger. Ensure oil and air hoses are properly installed and
securely clamped.
2) Use new gaskets. Adjust accelerator cable (if necessary).\
Refill engine oil and coolant. Check for oil and coolant leaks.
Tighten all bolts to specification. See TORQUE SPECIFICATIONS table.
TORQUE SPECIFICATIONS
TORQUE SPECIFICATIONS TABLE








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Applications Ft. Lbs. (N.m)
Fuel Tank Nuts ............................. 15-22 (20-30)

CAMSHAFT TIMING BELT REPLACEMENT INFORMATION
CAUTION: Failure to replace a faulty camshaft timing belt may result
in serious engine damage.
The condition of camshaft drive belts should always be
checked on vehicles which have more than 50,000 miles. Although some
manufacturers do not recommend belt replacement at a specified
mileage, others require it at 60,000-100,000 miles. A camshaft drive
belt failure may cause extensive damage to internal engine components
on most engines, although some designs do not allow piston-to-valve
contact. These designs are often called "Free Wheeling".
Many manufacturers changed their maintenance and warranty
schedules in the mid-1980's to reflect timing belt inspection and/or
replacement at 50,000-60,000 miles. Most service interval schedules in
this manual reflect these changes.
Belts or components should be inspected and replaced if any
of the following conditions exist:
* Cracks Or Tears In Belt Surface
* Missing, Damaged, Cracked Or Rounded Teeth
* Oil Contamination
* Damaged Or Faulty Tensioners
* Incorrect Tension Adjustment
Replace camshaft timing belt at 60,000 mile intervals.
SEVERE & NORMAL SERVICE DEFINITIONS
NOTE: Use the Severe Service schedule if the vehicle to be serviced
is operated under ANY (one or more) of these conditions:
Service is recommended at mileage intervals based on vehicle
operation. Service schedules are based on the following primary
operating conditions.
Normal Service
* Driven More Than 10 Miles Daily
* No Operating Conditions From Severe Service Schedule
Severe Service (Unique Driving Conditions)
* Short Trips In Freezing Temperatures
* Towing Or Commercial Use
* Driving Off-Road Or In Salty Or Sandy Areas
* Severe Dust Conditions
* Hot Weather, Stop-And-Go Driving
* Extensive Idling
SEVERE SERVICE REQUIREMENTS (PERFORM W/SERVICE SCHEDULES)
NOTE: The following services are to be performed on vehicles
subjected to severe service. See SEVERE & NORMAL SERVICE
DEFINITIONS. This service is to be performed in addition
to the normal services listed in the NORMAL MAINTENANCE
SERVICE SCHEDULES.
SEVERE SERVICE CONDITIONS/ACTIONS TABLE








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Condition  Action  Item  Perform Every (1) 

Light comes on with the ignition switch in the "ON" position
as a bulb check, but should go out shortly after engine is started. If
light remains on or comes on while driving, it indicates low oil
pressure and possible system malfunction. Have the system checked and
serviced immediately. Do not operate vehicle until cause is located
and corrected.
ALTERNATOR WARNING LIGHT
Light comes on with the ignition switch in the "ON" position
as a bulb check and goes out after engine is started. If light remains
on or comes on while driving, it indicates possible fault in the
electrical charging system. The alternator belt may be loose or
broken. Have the system checked and serviced promptly. Do not drive
vehicle if alternator belt is loose or broken.
"BRAKE" WARNING LIGHT
Light comes on with the ignition switch in the "ON" position
as a bulb check and goes out after engine is started. Light will also
come on with the parking brake fully or partially engaged. If light
remains on or comes on at any other time, it indicates low brake fluid
level in the master cylinder reservoir or the parking brake switch may
be damaged. Have the system checked and serviced immediately if brake
fluid level is low. Do not continue driving if further trouble is
experienced.
"CHECK ENGINE" WARNING LIGHT (IF EQUIPPED)
Light is designed to come on briefly with the ignition switch
in the "ON" position as a bulb check. If light remains on or comes on
while driving, it indicates fault in an exhaust gas related component
and the system is not functioning properly. Have the system checked
and serviced as soon as possible.
"MAINTENANCE REQUIRED" WARNING LIGHT (IF EQUIPPED)
Light comes on at 50,000 miles, 80,000 miles, 100,000 miles
and 120,000 miles (150,000 miles on 1990-91 models) as a service
reminder that it is time for the periodic maintenance of the emission
control system. Have the system inspected and serviced as necessary
when light comes on. Continued operation of vehicle without having
system serviced after warning light comes on may adversely affect
proper performance of the emission control system. Reset warning
light, after the system has been checked, by pushing the reset switch
in front of the combination meter. Remove the warning light bulb after
the last maintenance service at 120,000 miles (150,000 miles on 1990-
91 models).
"A/T TEMPERATURE" WARNING LIGHT (IF EQUIPPED)
Light comes on when the automatic transmission fluid
temperature becomes abnormally high. If light comes on, reduce engine
speed, stop car and put it in "P" (Park) position. Leave engine
running until light goes out. Normal vehicle operation may be resumed
after light has gone out. If light does not go out, have the system
checked and serviced as necessary.
WHEEL LOCK INDICATOR LIGHT (IF EQUIPPED)
Light comes on when automatic free-wheeling hubs are locked.
If ignition is turned off, indicator light will not come on when

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MECHANICAL CHECKS
ENGINE COMPRESSION
Check engine compression with engine at normal operating
temperature at specified cranking speed, all spark plugs removed and
throttle wide open.
COMPRESSION SPECIFICATIONS









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Application (1) Specification
Compression Ratio
1.5L (VIN A) ...................... 9.4:1
1.6L (VIN Y) ...................... 9.2:1
1.8L (VIN T) ...................... 9.0:1
2.0L (VIN R) ...................... 9.0:1
2.0L (VIN U) ...................... 9.0:1
2.0L (VIN V) ...................... 8.5:1
2.4L (VIN W) ...................... 8.5:1
3.0L (VIN B) ..................... 10.0:1
3.0L (VIN C) ...................... 8.0:1
3.0L (VIN S) ...................... 8.9:1
Compression Pressure ( 2)
1.5L (VIN A) ....... 137 psi (9.6 kg/cm
)
1.6L (VIN Y) ...... 171 psi (12.0 kg/cm)
1.8L (VIN T) ....... 131 psi (9.2 kg/cm)
2.0L (VIN R) ....... 137 psi (9.6 kg/cm)
2.0L (VIN U) ....... 114 psi (8.0 kg/cm)
2.0L (VIN V) ....... 119 psi (8.4 kg/cm)
2.4L (VIN W) ....... 119 psi (8.4 kg/cm)
3.0L (VIN B) ....... 139 psi (9.8 kg/cm)
3.0L (VIN C) ....... 115 psi (8.1 kg/cm)
3.0L (VIN S) ....... 119 psi (8.4 kg/cm)
( 1) - See A - ENGINE/VIN ID article in the
ENGINE PERFORMANCE Section for VIN
information.
( 2) - Maximum variation between cylinders is
14 psi (1.0 kg/cm
)








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VALVE CLEARANCE
NOTE: Valve adjustment is required on 1.5L engines only. Check
adjustment at 15,000 mile intervals.
VALVE CLEARANCE SPECIFICATIONS - 1.5L









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Application ( 1) In. (mm)
Hot Engine
Intake ....................... .006 (.15)
Exhaust ...................... .010 (.25)
Cold Engine
Intake ....................... .003 (.07)
Exhaust ...................... .007 (.17)
( 1) - Adjust valves with engine hot.









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I - S YSTE M /C O M PO NEN T T E STS

1991 M it s u bis h i M onte ro
1991 ENGINE PERFORMANCE
System & Component Testing
Chrysler Motors: Ram-50
Mitsubishi: Montero, Pickup
INTRODUCTION
Before testing separate components or systems, perform
procedures in F - BASIC TESTING article in the ENGINE PERFORMANCE
Section. Since many computer controlled and monitored components set a
trouble code if they malfunction, also perform procedures in G - TESTS
W/CODES article in the ENGINE PERFORMANCE Section.
NOTE: Testing individual components does not isolate shorts or
opens. Perform all voltage tests with a Digital
Volt-Ohmmeter (DVOM) with a minimum 10-megohm input
impedance, unless stated otherwise in test procedure. Use
ohmmeter to isolate wiring harness shorts or opens.
COMPUTERIZED ENGINE CONTROLS
CONTROL UNIT
NOTE: To identify ECU power and ground circuits, see appropriate
L - WIRING DIAGRAMS article in the ENGINE PERFORMANCE
Section.
Ground Circuits
1) ECU is located near right kick panel. Turn ignition off.
Using an ohmmeter, check for continuity between ground and ECU
terminals No. 101 and 106. Resistance should be zero ohms. If
resistance is not zero ohms, repair open circuit between ECU connector
and ground.
2) Connect voltmeter negative lead to ground. Connect
positive lead to ECU ground terminals as in step 1). With vehicle
running, voltmeter should indicate less than one volt. If voltmeter
reading is greater than one volt, check for open, corrosion or loose
connection in ground circuit.
Power Circuits
ECU is located near right kick panel. Turn ignition on. Check
for battery voltage on ECU terminals No. 102 and 107. If battery
voltage is not present, check operation of MPI control relay. See
RELAYS under MOTORS, RELAYS & SOLENOIDS.
ENGINE SENSORS & SWITCHES
BAROMETRIC PRESSURE SENSOR
Sensor is a component part of airflow sensor assembly. See G
- TESTS W/CODES article in the ENGINE PERFORMANCE Section.
COOLANT TEMPERATURE SENSOR
1) Remove coolant temperature sensor located near thermostat
housing (2-wire connector). Place end of sensor in water with terminal\

95C). Disconnect oxygen sensor connector. See Fig. 5. Connect
ohmmeter between heater terminals of oxygen sensor connector as
specified in OXYGEN SENSOR 4-WIRE CONNECTOR TERMINAL IDENTIFICATION
table. This test checks resistance of oxygen sensor heater element.
Fig. 5: O2 Sensor Connector Term. ID
Courtesy of Mitsubishi Motor Sales of America.
2) When oxygen sensor is at 68
F (20C), resistance should be
approximately 12 ohms (20 ohms on 3.0L models). If resistance is not
within specification, replace oxygen sensor.
CAUTION: DO NOT apply battery voltage to oxygen sensor output
terminals. Damage to oxygen sensor could result.
3) Apply battery voltage to oxygen sensor heater terminals as
specified in OXYGEN SENSOR 4-WIRE CONNECTOR TERMINAL IDENTIFICATION
table. This heats oxygen sensor heater element.
4) Connect digital voltmeter between output terminals
specified in OXYGEN SENSOR 4-WIRE CONNECTOR TERMINAL IDENTIFICATION
table. Repeatedly race engine and observe oxygen sensor output
voltage. If oxygen sensor output voltage is not within 0.6-1.0 volt,
replace oxygen sensor.
OXYGEN SENSOR 4-WIRE CONNECTOR TERMINAL ID TABLE









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Heater Output

MOTORS
ISC Motor
See IDLE CONTROL SYSTEM.
RELAYS
NOTE: For internal wiring diagram of MPI control relay, see
appropriate L - WIRING DIAGRAMS article in the ENGINE
PERFORMANCE Section.
MPI Control Relay (Montero, Pickup 3.0L & Ram-50 3.0L)
1) MPI control relay is located near right kick panel. Check
for battery voltage at terminal No. 10 of relay connector. See Fig. 9.
If battery voltage is present, go to step 3). If battery voltage is
not present, check circuit between relay and battery, including
fusible link No. 1.
Fig. 9: MPI Control Relay Connector Term. ID (10 Pin)
Courtesy of Mitsubishi Motor Sales of America.
2) Apply battery voltage to terminal No. 10. Battery voltage
should not be present at terminals No. 4 and 5. Apply battery voltage
to terminal No. 10, and ground terminal No. 8. Battery voltage should
now be present at terminals No. 4 and 5.
3) Apply battery voltage to terminal No. 3. Battery voltage
should not be present at terminal No. 2. Apply battery voltage to
terminal No. 3, and ground terminal No. 7. Battery voltage should now
be present at terminal No. 2.
4) Apply battery voltage to terminal No. 9. Battery voltage
should not be present at terminal No. 2. Apply battery voltage to
terminal No. 9, and ground terminal No. 6. Battery voltage should now
be present at terminal No. 2. Replace relay if it does not test as
specified.
MPI Control Relay (Pickup 2.4L & Ram-50)
1) MPI control relay is located near right kick panel. Check
for battery voltage at terminal No. 4 of relay connector. See Fig. 10.
If battery voltage is present, go to step 3). If battery voltage is

step. If there is continuity, replace relay.
3) Check diode operation between terminals No. 6 and 8. If
there is continuity in only one direction, go to next step. If there
is no continuity in either direction or if there is continuity in both
directions, replace relay.
4) Measure resistance between terminals No. 6 and 7. If
resistance is approximately 35 ohms, go to next step. If resistance is
not approximately 35 ohms, replace relay.
5) Measure resistance between terminals No. 2 and 5 and
between terminals No. 3 and 5. In both tests, if resistance is
approximately 95 ohms, go to next step. If resistance is not
approximately 95 ohms, replace relay.
6) Connect positive lead of 12-volt source to terminal No. 7
and negative lead to terminal No. 6. If there is continuity between
terminals No. 1 and 4, go to next step. If there is no continuity,
replace relay.
7) Connect positive lead of 12-volt source to terminal No. 5
and negative lead to terminal No. 2. If there is continuity between
terminals No. 1 and 4, go to next step. If there is no continuity,
replace relay.
8) Connect positive lead of 12-volt source to terminal No. 5
and negative lead to terminal No. 3. If there is continuity between
terminals No. 1 and 4, go to next step. If there is no continuity,
replace relay.
9) Connect positive lead of 12-volt source to terminal No. 8
and negative lead to terminal No. 6. If there is continuity between
terminals No. 3 and 4 and between terminals No. 2 and 4, relay is
okay. If there is no continuity, replace relay.
SOLENOIDS
Fuel Pressure Control Solenoid Valve
See FUEL DELIVERY under FUEL SYSTEM.
Fuel Injector Solenoids
See FUEL CONTROL under FUEL SYSTEM.
FUEL SYSTEM
FUEL DELIVERY
NOTE: For fuel system pressure testing, see F - BASIC TESTING
article in the ENGINE PERFORMANCE Section.
FUEL CONTROL
Fuel Injectors
1) Using a stethoscope, check operating sound of injector(s)\
during engine cranking or idling. If clicking sound is heard,
injectors are okay. If clicking sound is not heard at each injector,
go to step 2).
2) Disconnect injector electrical connector. Measure
resistance between injector connector terminals. At 68
F (20C), if
resistance is not 13-16 ohms, replace injector.
3) If resistance is within specification, check injector
wiring circuit for open or short to ground. If wiring circuit tests
okay, replace injector.
IDLE CONTROL SYSTEM
NOTE: ISC motor adjusts throttle plate angle to regulate idle air

right several times. Start engine, and turn steering wheel back and
forth to raise fluid temperature to approximately 122-140F (50-60C).
3) With engine idling, gradually close shutoff valve of
pressure gauge to increase hydraulic pressure. If idle speed does not
increase 200-250 RPM when fluid pressure reaches 213-284 psi (15-20
kg/cm
), replace power steering idle-up switch.
4) Gradually open shutoff valve. If engine speed does not
return to curb idle speed between 100-142 psi (7-10 kg/cm
), replace
power steering idle-up switch. Remove testing equipment. Bleed air
from system as in step 2).
IGNITION SYSTEM
NOTE: For basic ignition checks, see F - BASIC TESTING article in
ENGINE PERFORMANCE Section.
TIMING CONTROL SYSTEMS
Crank Angle Sensor
Crank angle sensor is located inside distributor on SOHC
engines and is attached to cylinder head on DOHC engines. If
malfunction occurs, Code 22 will set. For testing procedure, see
appropriate G - TESTS W/CODES article in the ENGINE PERFORMANCE
Section.
EMISSION SYSTEMS & SUB-SYSTEMS
EXHAUST GAS RECIRCULATION (EGR)
System Testing (Federal)
1) Disconnect Green-striped hose from throttle body, and
connect vacuum pump to hose end. Plug nipple where hose was connected
to throttle body. When engine is cold, 122
F (50C) or less, and at
idle, apply vacuum to disconnected hose. If idle does not change and
vacuum bleeds down, system is okay.
2) When engine is hot, 205
F (95C), and at idle, apply 1.8
in. Hg. If idle does not change and vacuum holds, system is okay.
Using a vacuum pump, apply 7.7 in. Hg. If idle becomes unstable or
engine stalls (and vacuum holds), system is okay.
System Testing (California)
1) Connect vacuum "T" fitting into Green-striped hose from
EGR valve, and connect vacuum gauge to vacuum tee. When engine coolant
temperature is 68
F (20C) or less and engine is idling, snap throttle
open to race engine. If no change in vacuum reading is detected on
gauge, system is okay.
2) When engine coolant temperature is 158
F (70C) or more
and engine is idling, snap throttle open to race engine. If vacuum
increases to 3.9 in. Hg or higher, system is okay.
3) Using vacuum pump, apply specified vacuum to open EGR
valve. See EGR VALVE SPECIFICATIONS table. If idle becomes unstable or
engine stalls, system is okay.
EGR Control Solenoid Valve (Pickup & Ram-50, California)
1) EGR control solenoid valve is located near left shock
tower. Label and disconnect vacuum hoses and wiring harness from
solenoid valve.
2) Connect hand vacuum pump to vacuum nipple where Green-
striped vacuum hose was connected. Apply vacuum and ensure vacuum does
not hold. Apply battery voltage to one terminal of solenoid, and
ground other. Ensure vacuum holds.

3) Using an ohmmeter, measure resistance between terminals of
solenoid valve. At room temperature, reading should be 36-44 ohms.
Replace solenoid if not to specification.
NOTE: EGR temperature sensor only determines if EGR is operating.
An inoperative sensor will not affect driveability or
exhaust emissions.
EGR Temperature Sensor (California)
1) Remove EGR temperature sensor from EGR valve. Place EGR
temperature sensor in water. While increasing water temperature,
measure resistance between wire terminals.
2) At a temperature of 122
F (50C), resistance should be 60,
000-80,000 ohms. At 212F (100C), resistance should be 11,000-14,000
ohms. Replace EGR temperature sensor if resistance differs
significantly from specifications.
EGR Valve
1) Remove EGR valve. Check valve for sticking, carbon
deposits and damage. Clean valve with solvent if necessary. Apply 19.8
in. Hg to valve diaphragm. If valve does not hold vacuum, replace
valve.
2) Apply specified vacuum to valve diaphragm. See CLOSED IN.
HG in EGR VALVE SPECIFICATIONS table. If valve begins to open below
specification, replace valve.
3) Apply specified vacuum to valve diaphragm. See OPEN IN. HG
in EGR VALVE SPECIFICATIONS table. If valve is not completely open at
or above specification, replace valve.
EGR VALVE SPECIFICATIONS TABLE









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Application Closed Open
In. Hg In. Hg
Montero ....................... 2.4 ........... 6.7
Pickup & Ram-50 ............... 1.2 ........... 9.4









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FUEL EVAPORATION
System Test
1) Disconnect Red-striped purge hose from throttle body, and
connect to hand vacuum pump. Plug nipple on throttle body where purge
hose was removed.
2) With engine coolant temperature at 140
F (60C) or less
and engine idling, apply 14.8 in. Hg. Vacuum should hold. Raise engine
speed to 3000 RPM and again apply 14.8 in. Hg. Vacuum should hold.
3) With engine coolant temperature at 158
F (70C) or more
and engine idling, apply 14.8 in. Hg. Vacuum should hold. Turn engine
off. Start engine and within 3 minutes of starting engine, apply
vacuum. Vacuum should bleed down.
4) With engine running for more than 3 minutes after
starting, raise engine speed to 3000 RPM and apply 14.8 in. Hg. Vacuum
should hold momentarily and then bleed down.
NOTE: In step 4), vacuum should bleed down continuously if vehicle
is at an altitude of 7200 ft. (2200 m) or higher or if
intake air temperature is 122
F (50C) or higher.
Purge Control Solenoid Valve
1) Purge control solenoid valve is located near left shock
tower. Label and disconnect both vacuum hoses from solenoid valve.
Disconnect electrical connector. Connect hand vacuum pump to solenoid