transmission MITSUBISHI MONTERO 1991 Manual PDF

Fig. 6: Engine Driveability & Automatic Transmission

Fig. 10: Manual Transmission & Clutch

connector portion of sensor slightly above water.
2) Gradually heat water and read resistance values across
terminal connectors. See COOLANT TEMPERATURE SENSOR RESISTANCE table.
If resistance is not within specification, replace sensor.
COOLANT TEMPERATURE SENSOR RESISTANCE TABLE









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TemperatureF (C) Ohms
Montero & Pickup 3.0L
32 (0) ............................. 5900
68 (20) ............................ 2500
104 (40) ........................... 2700
176 (80) ............................ 300
All Others
32 (0) ............................. 5900
68 (20) ............................ 2500
104 (40) ........................... 1100
176 (80) ............................ 300









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CRANK ANGLE SENSOR
See IGNITION SYSTEM.
DETONATION SENSOR
See IGNITION SYSTEM.
EGR TEMPERATURE SENSOR
California
See EXHAUST GAS RECIRCULATION (EGR) under EMISSION SYSTEMS &
SUB-SYSTEMS.
IDLE POSITION SWITCH
NOTE: Idle position switch is incorporated in idle speed control
motor assembly, motor position sensor or throttle position
sensor, depending upon vehicle application.
Pickup 2.4L & Ram-50 2.4L
1) Disconnect motor position sensor (MPS) connector. Connect\
ohmmeter lead between ground and MPS connector terminal No. 4. See
Fig. 2 .
2) With accelerator pedal pressed, no continuity should be
present. With accelerator pedal released, continuity should be
present. If switch continuity is not as specified, replace MPS.
Montero, Pickup 3.0L & Ram-50 3.0L
1) Disconnect throttle position sensor (TPS) connector.
Connect ohmmeter between TPS connector terminals No. 1 and 2. See
Fig. 6 .
2) With accelerator pedal pressed, no continuity should be
present. With accelerator pedal released, continuity should be
present. If idle switch continuity is not as specified, replace TPS.
INHIBITOR SWITCH
Automatic Transmission
Switch is mounted to automatic transaxle, near shift lever

input device usage on specific models, see appropriate wiring diagram
in M - WIRING DIAGRAMS.
Air Conditioner Switch
When A/C is turned on, signal is sent to ECU. With engine at
idle, ECU increases idle speed through Idle Speed Control (ISC) motor.\
Airflow Sensor
Incorporated in airflow sensor assembly, airflow sensor is a
Karmen Vortex-type sensor which measures intake airflow rate.
Intake air flows through tunnel in airflow sensor assembly.
Airflow sensor transmits radio frequency signals across direction of
incoming airflow, downstream of vortex. Intake air encounters vortex,
causing turbulence in tunnel.
Turbulence disrupts radio frequency, causing variations in
transmission. Airflow sensor converts frequency transmitted into a
proportionate electrical signal which is sent to ECU.
Airflow Sensor Assembly
Mounted inside air cleaner, incorporates airflow sensor,
atmospheric pressure sensor and intake air temperature sensor.
Atmospheric (Barometric) Pressure Sensor
Incorporated in the airflow sensor assembly, converts
atmospheric pressure to electrical signal which is sent to ECU. ECU
adjusts air/fuel ratio and ignition timing according to altitude.
Coolant Temperature Sensor
Converts coolant temperature to electrical signal for use by
ECU. ECU uses coolant temperature information for controlling fuel
enrichment when engine is cold.
Crankshaft Angle & TDC Sensor Assembly
Assembly is located in distributor on SOHC engines. On DOHC
engines, which use Direct (or Distributorless) Ignition System (DIS)\
,
assembly is separate unit mounted in place of distributor. Assembly
consists of triggering disc (mounted on shaft) and stationary optical
sensing unit. Camshaft drives shaft, triggering optical sensing unit.
ECU determines crank angle and TDC based on signals received from
optical sensing unit.
Detonation Sensor (Turbo Only)
Located in cylinder block, senses engine vibration during
detonation (knock). Sensor converts vibration into electrical signal.
ECU retards ignition timing based on this signal.
Engine Speed (Tach Signal)
ECU uses ignition coil tach signal to determine engine speed.
Idle Position Switch
On all DOHC engines and Sigma 3.0L, idle position switch is
separate switch mounted on throttle body. On all other models, idle
position switch is incorporated in ISC motor or throttle position
sensor, depending on vehicle application. When throttle valve is
closed, switch is activated. When throttle valve is at any other
position, switch is deactivated. This input from idle position switch
is used by ECU for controlling fuel delivery time during deceleration.
Ignition Timing Adjustment Terminal
Used for adjusting base ignition timing. When terminal is
grounded, ECU timing control function is by-passed, allowing base
timing to be adjusted.

Inhibitor Switch (Automatic Transmission Only)
Inhibitor switch senses position of transmission select
lever, indicating engine load due to automatic transmission
engagement. Based on this signal, ECU commands ISC motor to increase
throttle angle, maintaining optimum idle speed.
Intake Air Temperature Sensor
Incorporated in airflow sensor assembly, this resistor-based
sensor measures temperature of incoming air and supplies air density
information to ECU.
Motor Position Sensor (MPS)
Incorporated in ISC motor (or separate unit on some models),
senses ISC motor plunger position and sends electrical signal to ECU.
Oxygen (O2) Sensor
Located in exhaust system, generates an output voltage.
Output voltage varies with oxygen content of exhaust gas stream. ECU
adjusts air/fuel mixture based on signals from oxygen sensor.
Power Steering Oil Pressure Switch
Detects increase in power steering oil pressure. When power
steering oil pressure increases, switch contacts close, signalling
ECU. ECU commands ISC motor, raising idle speed to compensate for drop
in engine RPM due to power steering load.
TDC Sensor
See CRANKSHAFT ANGLE & TDC SENSOR ASSEMBLY.
Throttle Position Sensor (TPS)
A variable resistor mounted on throttle body. ECU uses
voltage signal received from TPS to determine throttle plate angle.
Vehicle Speed Sensor
Located in speedometer in instrument cluster, uses a reed
switch to sense speedometer gear revolutions. ECU uses gear
revolutions to determine vehicle speed.
OUTPUT SIGNALS
NOTE: Vehicles are equipped with different combinations of
computer-controlled components. Not all components listed
below are used on every vehicle. For theory and operation on
each output component, refer to the system indicated in
brackets after component.
CHECK ENGINE Light
See SELF DIAGNOSTIC SYSTEM.
EGR Control Solenoid Valve
See EXHAUST GAS RECIRCULATION (EGR) CONTROL under EMISSION
SYSTEMS.
Fuel Injectors
See FUEL CONTROL under FUEL SYSTEM.
Fuel Pressure Control Solenoid Valve (Turbo Only)
See FUEL DELIVERY under FUEL SYSTEM.
Fuel Pressure Regulator
See FUEL DELIVERY under FUEL SYSTEM.
Fuel Pump Relay (MPI Control Relay)

motor to increase idle speed. To prevent A/C compressor from switching
on before idle speed has increased, ECU momentarily opens A/C relay
circuit.
Idle Speed Control (ISC) Motor
Controls pintle-type air valve (DOHC engines) or throttle
plate angle (SOHC engines) to regulate volume of intake air at idle.
During start mode, ECU controls idle intake air volume
according to coolant temperature input. After starting, with idle
position switch activated (throttle closed), fast idle speed is
controlled by ISC motor and fast idle air control valve (if equipped).\
When idle switch is deactivated (throttle open), ISC motor
moves to a preset position in accordance with coolant temperature
input.
When automatic transmission (if equipped) is shifted from
Neutral to Drive, A/C is turned on or power steering pressure reaches
a preset value, ECU signals ISC motor to increase engine RPM.
Fast Idle Air Control Valve
Some models use a coolant temperature-sensitive fast idle air
control valve, located on throttle body, to admit additional intake
air volume during engine warm-up. Control valve closes as temperature
increases, restricting by-pass airflow rate. At engine warm-up, valve
closes completely.
IGNITION SYSTEMS
DIRECT IGNITION SYSTEM (DIS) - DOHC ENGINES
Ignition system is a 2-coil, distributorless ignition system.
Crankshaft angle and TDC sensor assembly, mounted in place of
distributor, are optically controlled.
Power Transistors & Ignition Coils
Based on crankshaft angle and TDC sensor inputs, ECU controls
timing and directly activates each power transistor to fire coils.
Power transistor "A" controls primary current of ignition coil "A" to
fire spark plugs on cylinders No. 1 and 4 at the same time. Power
transistor "B" controls primary current of ignition coil "B" to fire
spark plugs on cylinders No. 2 and 3 at the same time.
Although each coil fires 2 plugs at the same time, ignition
takes place in only one cylinder since the other cylinder is on its
exhaust stroke when plug fires.
ELECTRONIC IGNITION SYSTEM - SOHC ENGINES
Mitsubishi breakerless electronic ignition system uses a disc
and optical sensing unit to trigger power transistor.
Power Transistor & Ignition Coil
Power transistor is mounted inside distributor with disc and
optical sensing unit. When ignition is on, ignition coil primary
circuit is energized. As distributor shaft rotates, disc rotates,
triggering optical sensing unit. ECU receives signals from optical
sensing unit. Signals are converted and sent to power transistor,
interrupting primary current flow and inducing secondary voltage.
IGNITION TIMING CONTROL SYSTEM
Ignition timing is controlled by ECU. ECU adjusts timing
based upon various conditions, such as engine temperature, altitude
and detonation (turbo vehicles only).

TR AN SFE R C ASE

1991 M it s u bis h i M onte ro
1991-94 TRANSFER CASES
Mitsubishi
Dodge; Ram-50
Mitsubishi; Pickup, Montero
APPLICATION
TRANSFER CASE APPLICATIONS TABLE








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Application ( 1) Transmission Model
Dodge
1991-93 Ram-50 (2.4L) .......................... V5M21-1
1991-93 Ram-50 (3.0L M/T) ...................... V5MT1-2
1991-93 Ram-50 (3.0L A/T) ...................... V4AC1-2
Mitsubishi
1991-92 Pickup ................................. V5MT1-2
1991 Montero (M/T) ............................. V5MT1-2
1991 Montero (A/T) ............................. V4AW2-2
1992 Montero (M/T) ......................... ( 2) V5MT1-3
1992 Montero (A/T) ......................... ( 2) V4AW2-3
1993-94 Montero (M/T) ...................... ( 2) V5MT1-2
1993-94 Montero (A/T) ........................ ( 2) R4AC1
( 1) - Transfer case is indicated by a -2 or -3 following the
transmission model number.
( 2) - Transfer cases for Montero are identical for automatic and
manual transmission models.









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DESCRIPTION
Transfer case is a part-time, 2-speed unit with a 3-piece
aluminum case. Transfer case has a floor-mounted shifter and integral
speedometer gear. In Montero a Viscous Coupling Unit (VCU) and center
differential allows 2WD-to-4WD shifting at speeds under 62 MPH and
full-time 4WD operation.
WARNING: When battery is disconnected, vehicles equipped with
computers may lose memory data. When battery power is
restored, driveability problems may exist on some vehicles.
These vehicles may require a relearn procedure. See the
COMPUTER RELEARN PROCEDURES article in the GENERAL
INFORMATION section.
TESTING
4WD INDICATOR CONTROL UNIT (MONTERO)
The 4WD indicator control unit is located behind radio or CD
player. Remove 4WD indicator control unit and disconnect harness.
Backprobe harness connector and measure voltage between terminal No. 8
(ground) and each respective terminal. Compare test results with
chart. See Fig. 1.
DETECTION SWITCH

Fig. 2: Detection Switch Testing Locations (Montero)
Courtesy of Mitsubishi Motor Sales of America.
REMOVAL & INSTALLATION
Removal
1) Remove negative battery cable. Remove transfer case skid
plate (if equipped). Scribe alignment marks and remove both drive
shafts. Drain oil from transfer case. Disconnect wiring harness from
back-up light switch, all 4WD switches and any other electrical
connectors (if equipped).
2) Disconnect speedometer cable from drive. Unclip cable from
case. Place transfer case shifter in "2H" position and transmission in
Neutral. Remove 6 bolts holding control lever assembly. Remove control
lever assembly and gasket.
3) Remove select plunger bore plug at right side of case.
Remove select spring and plunger. Remove change shifter spring pin.
Remove change shifter. Remove transfer case mount. Remove 4 bolts and
2 nuts holding transfer case to adapter. Remove transfer case from
vehicle.

Installation
1) Position transmission shifter in Neutral and transfer case
lever in "2H" position. Install neutral return plungers and springs in
holes on top of adapter. Tighten plug until it is flush with adapter
surface. Cover plug threads with sealant.
2) Coat inside of change shifter with grease. Ensure change
shifter pin protrudes 1/8" above change shifter when installed. Mount
detent plunger spring and install plug (if equipped). To complete
installation, reverse removal procedure. Fill transfer case with API
GL-4 or higher 75W-90 or 75W-85W gear oil.
Fig. 3: Exploded View Of Transfer Case (Ram-50)
Courtesy of Mitsubishi Motor Sales of America.

2) Remove 2 seal plugs. Remove 2 poppet springs and steel
balls. Shift transfer case to "4WD" and pull high-low shift rail out,
in rear cover direction. Remove interlock plunger. Remove pulse
generator (if equipped), front output shaft cover and pulse rotor (if\
equipped). Remove snap ring from rear bearing on output shaft. Remove
chain cover, oil guide and side cover. Remove countershaft locking
plate. Remove countershaft.
3) Remove countergear, 2 thrust washers, 2 needle bearings
and spacer through side cover opening. Remove snap ring, spring
retainers and spring from 2WD-4WD shift rail. Remove front output
shaft, rear output shaft and chain as assembly.
4) Remove 2WD-4WD shift fork and distance piece. Drive out
2WD-4WD shift rail spring pin. Remove 2WD-4WD shift rail and lug.
Remove high-low shift fork and high-low synchronizer sleeve. Remove
needle bearing and snap ring from input gear. Remove input gear
assembly.
5) If either control shaft or input gear oil seals are to be
replaced, drive out roll pin from transmission control change shifter.
Separate transfer case from adapter. See Fig. 3.
Disassembly (Montero)
1) Remove dynamic damper, 5 detection switches and 3 steel
balls. Remove poppet plug, spring and steel ball. Remove speedometer
gear assembly. Remove output shaft rear cover, spacers, dust seal
guard and oil seals. Front output shaft cover, wave spring and spacer
(if equipped).
2) Remove high-low shift rail plug and high-low shift fork
spring pin. Shift transfer case to "4WD". Remove rear cover and high-
low shift rail. Remove interlock plunger. Remove rear output shaft
(viscous coupling) assembly and center differential assembly. Remove
2WD-4WD synchronizer assembly, chain and front output shaft from
transmission as a unit. With White paint make match marks in grooves
of 2WD-4WD synchronizer in 3 places. With White paint make match marks
on spline projections of 2WD-4WD synchronizer sleeve in 3 places.
Refer to match marks during reassembly.
3) Remove snap ring, spring seat, spring, 2WD-4WD shift fork
and 2WD-4WD synchronizer sleeve. Remove differential lock hub, oil dam
cover and bearing retainer. Remove side cover and gasket. Remove
transfer counter gear shaft, transfer counter gear, thrust washer,
needle bearings and spacer. Remove transfer drive shaft assembly.
Remove high-low shift fork assembly and clutch sleeve. Remove transfer
input gear assembly.
4) Remove 2WD-4WD shift lug spring pin, spring, spring
retainer 2WD-4WD shift lug and shift rail. Remove input gear oil seal,
baffle plate, dust seal guard and front output shaft oil seal. See
Fig. 4 .
COMPONENT DISASSEMBLY & REASSEMBLY
OUTPUT SHAFT ASSEMBLY (MONTERO)
Disassembly & Reassembly (Rear Shaft)
Remove snap ring and press ball bearing off without putting
pressure on vicious coupling. Remove viscous coupling. To install,
reverse removal procedure. When installing new snap ring, select
thickest ring that will fit into groove. Acceptable clearance is 0-.
003" (0-.08 mm).
Disassembly & Reassembly (Front Shaft)
Remove front bearing. Remove rear bearing. To install reverse
removal procedure.