MITSUBISHI MONTERO 1991 Service Manual

by-pass volume.
IDLE SPEED CONTROL (ISC) MOTOR OPERATION TEST
CAUTION: DO NOT apply more than 6 volts to ISC motor.
Pickup 2.4L & Ram-50 2.4L
Connect 6-volt DC source across terminals No. 1 and 2 of ISC
motor connector. See Fig. 11. Reverse leads of 6-volt source. If motor
does not operate in both directions, replace ISC motor assembly.
Fig. 11: ISC Motor Connector Term. ID (2 Pin)
Courtesy of Mitsubishi Motor Sales of America.
Montero, Pickup 3.0L & Ram-50 3.0L
1) Remove throttle body from intake plenum. Remove ISC motor
from throttle body. Apply 6-volt source parallel to terminals No. 2
and 5 of ISC motor connector. See Fig. 12.

Fig. 12: ISC Motor Connector Term. ID (6 Pin)
Courtesy of Mitsubishi Motor Sales of America.
2) Apply source ground lead to ISC motor connector terminals
No. 3 and 6. Note slight movement of ISC motor plunger. Remove ground
leads from terminals No. 3 and 6.
3) Apply and remove source ground at terminals No. 1 and 6, 1
and 4, 3 and 4, and 3 and 6. Note slight movement of ISC motor plunger
during each phase of test.
4) Beginning at terminal No. 6, reverse grounding sequence
following same procedure specified in step 2). If motor does not
operate when grounding any of specified terminals, replace ISC motor.
IDLE SPEED CONTROL (ISC) MOTOR RESISTANCE TEST
Pickup 2.4L & Ram-50 2.4L
Disconnect ISC motor connector. Connect ohmmeter between
terminals No. 1 and 2 of ISC motor connector. See Fig. 11. If
resistance is not 5-35 ohms at 68
F (20C), replace ISC motor
assembly.
Montero, Pickup 3.0L & Ram-50 3.0L
Measure resistance between terminals No. 1 and 2, 2 and 3, 4
and 5, and 5 and 6 of ISC motor connector. See Fig. 12. In each case,
if resistance is not 28-33 ohms at 68
F (20C), replace ISC motor

assembly.
IDLE-UP SYSTEMS
Power Steering Idle-Up System Test
1) Disconnect pressure hose from power steering pump. Connect
in-line a pressure gauge and hoses capable of handling 300 psi (21
kg/cm
). Also connect a shut-off valve in-line with pressure gauge.
See Fig. 13 .
Fig. 13: Connecting Pressure Gauge Shutoff Valve Assembly
Courtesy of Mitsubishi Motor Sales of America.
2) Bleed air from system by disabling ignition system and
cranking engine while turning steering wheel completely from left to

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

valve nipple where Red-striped hose was connected. Apply vacuum to
solenoid valve. Vacuum should hold.
2) Apply battery voltage to terminals of solenoid valve.
Vacuum should bleed down when voltage is applied to terminals. Using
an ohmmeter, check resistance across solenoid valve terminals. Reading
should be 36-44 ohms at 68
F (20C). If reading is not within
specification, replace valve.
POSITIVE CRANKCASE VENTILATION (PCV)
PCV Valve
Remove PCV valve, and insert thin screwdriver into threaded
end of valve to ensure plunger moves.

SYSTE M W IR IN G D IA G RAM S

1991 M it s u bis h i M onte ro
1991 System Wiring Diagrams
Mitsubishi - Montero
COOLING FAN
Cooling Fan Circuit
DEFOGGERS

Defogger Circuit
HORN

Horn Circuit
POWER DOOR LOCKS

Back Door Lock Circuit