1991 MITSUBISHI MONTERO engine

Adjusting Screw (SAS) and throttle lever. See Fig. 4. Loosen TPS
mounting screws. Rotate TPS fully counterclockwise. Check for
continuity between Yellow/Red wire and Black wire terminals of TPS.
3) Rotate TPS clockwise until ohmmeter registers no
continuity. Tighten TPS mounting screws. Reconnect TPS electrical
connector.
4) Use a digital voltmeter to backprobe terminal No. 19
(Brown/Red wire) and terminal No. 24 (Brown wire) at Engine Control
Unit (ECU) wiring harness on SOHC vehicles, or terminal No. 64
(Brown/Red wire) and terminal No. 72 (Black wire) on DOHC vehicles.
Turn ignition on. DO NOT start engine. Check TPS output voltage.
5) If TPS output voltage is 0.4-1.0 volt, go to step 6). If
TPS output voltage is not 0.4-1.0 volt, check TPS and wiring harness
for damage or malfunction. Replace TPS or repair wiring harness if
necessary and go to step 6).
6) Remove feeler gauge. Turn ignition off. Disconnect
voltmeter from ECU connector. Operate engine at idle for about 5
minutes to ensure engine idles smoothly and within specification.
IDLE POSITION SWITCH
NOTE: Idle position switch is preset by manufacturer. Adjustment
is usually not necessary. If other procedures in this
article require adjustment of idle position switch or if
switch setting has been changed, adjust switch as follows.
1.6L Mirage, 2.0L Eclipse & 2.0L Galant (DOHC)
1) Loosen throttle cable. Disconnect electrical connector
from idle position switch. See Fig. 5. Loosen lock nut at base of
switch. Turn switch counterclockwise until throttle valve is fully
closed.
2) Connect ohmmeter between switch terminal and switch body
(ground). Turn idle position switch clockwise until ohmmeter registers\
continuity. At this point, throttle valve should begin to open.
3) Turn switch 15/16 of a turn beyond contact point. Tighten
lock nut at base of idle position switch, holding switch to prevent it
from turning while tightening.
4) Adjust throttle cable. Adjust basic idle speed. See BASIC
IDLE SPEED. Adjust TPS. See TPS ADJUSTMENT.
All Other Models
Idle position switch is incorporated in ISC motor and is
automatically adjusted when TPS is adjusted. See TPS ADJUSTMENT.
Fig. 5: Idle Position Switch Location (1.6L & 2.0L (VIN R &U))
Courtesy of Mitsubishi Motor Sales of America.

terminal "B" and negative lead to positive battery terminal. Reconnect
negative battery cable.
3) Start engine. Turn accessories on and adjust engine speed
until ammeter indicates 20 amps, and note voltmeter reading. If
voltmeter indicates .2 volt or less, system is okay.
4) If voltage is greater than .2 volt, wiring is defective
between alternator terminal "B", fusible link and battery positive
terminal. Disconnect negative battery cable, and remove test
equipment.
ALTERNATOR OUTPUT TEST
NOTE: During alternator output test, a slightly discharged battery
should be used as a fully charged battery may not allow full
alternator output.
1) Turn ignition switch to OFF position. Disconnect negative
battery cable. Disconnect alternator output wire from terminal "B".
Install positive lead of 100-amp ammeter to terminal "B" and negative
lead to disconnected output lead.
CAUTION: Tighten each connection securely as heavy current flow will
exist. DO NOT use clips on ammeter.
2) Connect positive voltmeter lead (0-20 volts) to alternato\
r
terminal "B" and negative lead to ground. Install tachometer, and
reconnect negative battery cable.
3) Ensure voltmeter indicates battery voltage. If no voltage
exists, an open circuit is present in wire between alternator terminal
"B" and battery negative terminal. Check grounds and fusible link.
4) Turn headlights on, and start engine. Set headlights at
high beam and heater switch on HIGH. Quickly accelerate engine speed
to 2500 RPM and note alternator output current registered on the
ammeter. Minimum output should be within specification. Refer to the
ALTERNATOR MINIMUM OUTPUT SPECIFICATIONS table.
NOTE: Output voltage changes with electrical load and temperature.
Ensure proper electrical load is applied while checking
output. Nominal output may not be obtained if alternator or
ambient temperature is excessive. Allow to cool, and recheck
output. Alternator output is stamped on metal plate attached
to alternator case.
5) If minimum output is not obtained and alternator wiring is
okay, repair alternator. Disconnect negative battery cable, and remove
test equipment.
REGULATED VOLTAGE TEST
NOTE: Ensure battery is fully charged and proper drive belt
tension exists.
1) Turn ignition switch to OFF position. Disconnect negative
battery cable. Install a digital voltmeter between alternator terminal
"S" and ground. See Fig. 10. Connect positive voltmeter lead to
terminal "S" of alternator. Connect negative voltmeter lead to ground.
2) Disconnect alternator output wire from terminal "B".
Install a 100-amp ammeter in series to terminal "B" and disconnected
output lead. Install positive lead of ammeter to terminal "B" and
negative lead to disconnected output wire. Install a tachometer, and
reconnect negative battery cable.
3) Turn ignition switch to ON position and ensure voltmeter
indicates battery voltage. If no voltage exists, an open circuit

exists in wire between alternator terminal "S" and positive battery
terminal or fusible link is blown.
4) Start engine. Ensure all lights and accessories are off.
Operate engine at 2500 RPM and read voltmeter when alternator output
current drops to 10 amps or less. Voltage regulator is okay if voltage
output is within specification. See REGULATOR VOLTAGE SPECIFICATIONS
table.
BENCH TESTING
RECTIFIER ASSEMBLY
1) Using ohmmeter, check for continuity between both diodes
and stator coil lead connection. See Fig. 11. Reverse leads. If
continuity exists in both directions, diode is shorted. Replace
rectifier assembly.
2) To check entire diode assembly, use an ohmmeter to check
for continuity between both ends of each diode. See Fig. 11. Switch
ohmmeter leads. Continuity should exist in one direction, but not
other. If no continuity exists or continuity exists in both
directions, diode is defective. Replace rectifier assembly.
Fig. 11: Testing Rectifier Assembly
Courtesy of Mitsubishi Motor Sales of America.
ROTOR

\003
F - B ASIC T E STIN G

1991 M it s u bis h i M onte ro
1991 ENGINE PERFORMANCE
Basic Diagnostic Procedures
Chrysler; Colt, Colt 200, Colt Vista, Ram-50, Stealth,
Summit
Mitsubishi; Eclipse, Galant, Mirage, Montero, Pickup, 3000GT
INTRODUCTION
The following diagnostic steps will help prevent overlooking
a simple problem. This is also where to begin diagnosis for a no start
condition. First step in diagnosing any driveability problem is
verifying customer's complaint with a test drive under conditions
problem reportedly occurred.
Before entering self-diagnostics, perform a careful and
complete visual inspection. Most engine control problems result from
mechanical breakdowns, poor electrical connections or
damaged/misrouted vacuum hoses. Before condemning computerized system,
perform each test listed in article.
NOTE: Perform all voltage tests with a Digital Volt-Ohmmeter (DVOM)\
with a minimum 10-megohm input impedance, unless stated
otherwise in test procedure.
PRELIMINARY INSPECTION & ADJUSTMENTS
VISUAL INSPECTION
Visually inspect all electrical wiring, looking for chafed,
stretched, cut or pinched wiring. Ensure electrical connectors fit
tightly and are not corroded. Ensure distributor cap and rotor are
free of cracks, carbon trails or contamination. Ensure vacuum hoses
are properly routed and not pinched or cut. See M - VACUUM DIAGRAMS
article in the ENGINE PERFORMANCE Section to verify routing and
connections (if necessary). Inspect air induction system for possible
vacuum leaks.
MECHANICAL INSPECTION
Compression
Check engine mechanical condition with a compression gauge,
vacuum gauge, or an engine analyzer. See engine analyzer manual for
specific instructions.
WARNING: DO NOT use ignition switch during compression tests. Use a
remote starter to crank engine. Fuel injectors on many models
are triggered by ignition switch during cranking mode, which
can create a fire hazard or contaminate engine's oiling
system.
COMPRESSION SPECIFICATIONS TABLE (1)









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Application Specification
psi (kg/cm)
1.5L (VIN X) .............................. 137 (9.6)
1.6L (VIN Y) ............................. 171 (12.0)
1.8L (VIN T) .............................. 131 (9.2)

2.0L (VIN R) DOHC ......................... 137 (9.6)
2.0L (VIN U) DOHC Turbo ................... 114 (8.0)
2.0L (VIN V) SOHC ......................... 119 (8.4)
2.4L (VIN W) SOHC ......................... 119 (8.4)
3.0L (VIN S) SOHC ......................... 119 (8.4)
3.0L (VIN B) DOHC ......................... 139 (9.8)
3.0L (VIN C) DOHC Turbo ................... 115 (8.1)
(1) - Maximum variation between cylinders 14 psi
(1.0 kg/cm
)








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Exhaust System Backpressure
Exhaust system can be checked with a vacuum or pressure
gauge. Remove O2 sensor or air injection check valve (if equipped).
Connect a 1-10 psi pressure gauge and run engine at 2500 RPM. If
exhaust system backpressure is greater than 1 3/4-2 psi, exhaust
system or catalytic converter is plugged. If a vacuum gauge is used,
connect vacuum gauge hose to intake manifold vacuum port and start
engine. Observe vacuum gauge. Open throttle part way and hold steady.
If vacuum gauge reading slowly drops after stabilizing, exhaust system
should be checked for a restriction.
FUEL PRESSURE
Basic diagnosis of fuel system should begin with determining
fuel system pressure.
FUEL INJECTED ENGINES
WARNING: ALWAYS relieve fuel pressure before disconnecting any fuel
injection-related component. DO NOT allow fuel to contact
engine or electrical components.
Fuel Pressure
1) On all models except Colt and Mirage, disconnect fuel pump
harness connector at fuel tank. On Colt and Mirage, remove rear seat
cushion to disconnect fuel pump harness connector.
2) On all models, start engine. Let engine run until it
stops. Turn ignition off. Disconnect negative battery terminal.
Connect fuel pump harness connector.
WARNING: Before disconnecting high pressure fuel hose at fuel delivery
pipe, cover fuel hose connection with a rag. Some residual
fuel pressure may still be in system.
3) On Galant 2.0L (DOHC), remove brace for access to high
pressure fuel delivery pipe. On all engines, disconnect high pressure
fuel hose at fuel delivery pipe.
4) Connect fuel pressure gauge with adapter between fuel
delivery pipe and high pressure hose. See Fig. 1. Connect negative
battery terminal. Connect battery voltage to fuel pump test terminal.
See FUEL PUMP TEST TERMINAL LOCATION table. Ensure no fuel leaks are
present. Disconnect battery voltage to fuel pump test terminal.

Fig. 1: Fuel Pressure Testing Connection ID (Typical Fuel Inj. Eng.)
Courtesy of Mitsubishi Motor Sales of America.
5) Start engine and let idle. Measure fuel pressure with
vacuum hose connected to fuel pressure regulator. Record fuel pressure
reading. Disconnect and plug vacuum hose from fuel pressure regulator.
Record fuel pressure reading. See REGULATED FUEL PRESSURE table.
6) Check for fuel pressure in fuel return hose by gently
pinching hose while increasing engine speed. If fuel volume is low,
fuel pressure in return hose will not be felt. Increase engine speed
to 2500-3000 RPM, 2-3 times. Return engine to idle. Fuel pressure
should not drop when engine is returned to idle.
7) Turn engine off. Ensure fuel pressure reading does not
decrease within 2 minutes. If a decrease is noted, monitor speed of
decrease.
8) If fuel pressure is lower than specification, fuel
pressure drops at idle after increasing engine speed to 2500-3000 RPM,
or no fuel pressure in fuel return hose can be felt, check for clogged
fuel filter, faulty fuel pressure regulator, or fuel pump.
9) If fuel pressure is higher than specification, check for a
faulty fuel pressure regulator or plugged fuel return line. If fuel
pressure does not change when vacuum hose to regulator is connected or
disconnected, check for a leaking or clogged vacuum hose to fuel
pressure regulator or faulty fuel pressure regulator.
10) If fuel pressure decreases suddenly after engine is
stopped, check valve within fuel pump is not seated. Replace fuel

pump. If fuel pressure drops slowly, fuel injector is leaking or fuel
pressure regulator valve seat is leaking. Check for faulty fuel
injector or fuel pressure regulator. Repair as required.
11) When fuel pressure test is complete, repeat fuel pressure
release procedure in steps 1) and 2) before disconnecting fuel
pressure gauge. Install new "O" ring at end of high pressure hose.
Check for fuel leaks.
FUEL PUMP TEST TERMINAL LOCATION TABLE









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Application Wire Color Location
Colt, Colt 200 ......... BLK/WHT .............. Center Of Firewall
Colt Vista ............. BLK/WHT ........ Right Center Of Firewall
Eclipse ................ BLK/WHT .......... Rear Of Battery Compt.
Galant ................. YEL/GRN ........... Left Rear Eng. Compt.
Mirage 1.5L ............ BLK/WHT .............. Center Of Firewall
Mirage 1.6L ............ BLK/BLU .............. Center Of Firewall
Montero .................. WHT .......... Right Center Of Firewall
Pickup ................. BLK/BLU ....... Right Side Of Eng. Compt.
Precis ................... YEL ............. Left Rear Eng. Compt.
Summit ................. BLK/WHT .............. Center Of Firewall
Ram-50 ................. BLK/BLU ....... Right Side Of Eng. Compt.
Stealth, 3000GT ........ BLK/BLU .......... Rear Of Battery Compt.









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REGULATED FUEL PRESSURE TABLE








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At Idle At Idle
w/Vacuum w/o Vacuum
Application psi (kg/cm
) psi (kg/cm)
Non-Turbo .................. 38 (2.7) ....... 47-50 (3.3-3.5)
Turbo
Except Eclipse A/T ....... 27 (1.9) ....... 36-38 (2.5-2.7)
Eclipse A/T .............. 33 (2.3) ....... 36-38 (2.9-3.2)









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Control Relay
Multipurpose relay switches power to vehicle sensors and
actuators including airflow sensor, crank angle sensor, idle speed
control, injectors and fuel pump. When ignition switch is turned to ON
position, ECU energizes coils controlling injectors, airflow sensor
and idle speed control. When ignition switch is turned to START
position, ECU energizes coils (through inhibitor switch on A/T models)\
to supply power to fuel pump. Relay failure will cause a no-start
condition. For testing procedure, see SYSTEM & COMPONENT TESTING
article.
IGNITION CHECKS
SPARK
Check for spark at coil wire (if applicable) and at each
spark plug wire using a high output spark tester. Check spark plug
wire resistance on suspect wires. For wire resistance specification,
see C - SPECIFICATIONS article in the ENGINE PERFORMANCE Section.
CRANK ANGLE SENSOR
For crank angle sensor testing procedure on all models except
Ram-50, Stealth, Eclipse, Laser, Pickup and 3000GT, see TEST NS-5:

TESTING CRANK ANGLE SENSOR CIRCUIT - G - TESTS W/CODES article in the
ENGINE PERFORMANCE section.
On Eclipse and Laser, see NS-4A: REPAIRING CRANK ANGLE SENSOR
in G - TESTS W/CODES - 1.8L article.
On Ram-50, Stealth, Pickup and 3000GT testing information not
available at time of publication.
DISTRIBUTORLESS IGNITION SYSTEM (DIS)
Ignition Coil Resistance (4-Cyl Vehicles Except Eclipse 2.0L)
1) Using a Digital Volt/Ohmmeter (DVOM), measure primary coi\
l
resistance between ignition coil connector terminals No. 2 and No. 3
(coils for cylinders No. 1 and No. 4) and terminals No. 1 and No. 3
(coils for cylinders No. 2 and No. 3). See Fig. 2.
Fig. 2: Testing Ignition Coil Primary Resistance (4-Cylinder)
Courtesy of Mitsubishi Motor Sales of America.
2) Measure secondary coil resistance between coil towers for
cylinders No. 1 and No. 4 and between coil towers for cylinders No. 2
and No. 3. See Fig. 3. Primary and secondary coil resistance should be
within specification. See DIS IGNITION COIL RESISTANCE table.
Fig. 3: Testing Ignition Coil Secondary Resistance (4-Cylinder)
Courtesy of Mitsubishi Motor Sales of America.