1991 MITSUBISHI MONTERO oil pressure

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).

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.

fluid to bring level to lower mark of dipstick if necessary. Recheck
fluid level after transmission is at normal operating temperature.
TRANSFER CASE
Drain plug is located on bottom of transfer case. Change
drain plug gasket whenever fluid is changed. On 3000GT, lubricant
level should be approximately .5" (13 mm) below fill hole on side of
transfer case. On all others models, lubricant level should be to
bottom of fill hole on side of transfer case.
HYDRAULIC CONTROL PRESSURE ADJUSTMENTS
LINE PRESSURE CHECK (EXCEPT MONTERO & PICKUP)
1) Set parking brake. Place shift lever in Neutral position.
Attach engine tachometer. Remove line pressure port plug located above
front transaxle shaft, forward of governor pressure port plug. On
Precis, line pressure port is located below bell housing, at front of
transaxle oil pan. Using appropriate adapter, attach pressure gauge.
2) Start engine, and bring to operating temperature. With
gear selector in Drive position, bring engine speed to 2500 RPM. Pull
throttle control cable (if equipped) wide open at transaxle side.
3) Line pressure should be 98-100 psi (6.9-7.0 kg/cm
) on
Mirage, or 124-127 psi (8.7-8.9 kg/cm) on all others. If line
pressure is not to specification, proceed to LINE PRESSURE ADJUSTMENT.
LINE PRESSURE ADJUSTMENT (EXCEPT MONTERO & PICKUP)
1) Drain transaxle fluid. Remove oil pan. Disconnect throttle
control cable from throttle cam. Remove oil temperature sensor (if
equipped). Disconnect solenoid connector. On some models, it may be
necessary to push solenoid wire harness connector and grommet into
transaxle case.
2) Remove oil filter screen and plate. Noting location and
length of bolts, remove valve body. DO NOT drop internal parts. Adjust
line pressure by turning regulator valve adjusting screw.
3) Turn adjusting screw counterclockwise to increase pressure
or clockwise to decrease pressure. One complete turn of adjusting
screw changes line pressure as follows.
* 3.7 psi (.26 kg/cm
) on Mirage with F3A21 Transaxle
* 5.4 psi (.39 kg/cm) on Precis
* 54 psi (3.8 kg/cm) on all others
4) After adjustment, reverse removal procedure to install.
Refill transaxle.
LINE PRESSURE (MONTERO)
1) Remove plug from line pressure take-off port located
behind transmission shift control lever. Install Hydraulic Pressure
Meter (MD998330) with Adapter (MD998206).
2) Place vehicle on dynamometer. Apply parking brake and
start engine. With brake applied, place transmission in Drive. Note
pressure at idle. Pressure should be 74-85 psi (5.2-6.0 kg/cm
).
3) Raise engine RPM to stall speed (2100-2400 RPM). Note lin\
e
pressure. Pressure should be 156-185 psi (11.0-13.0 kg/cm
).
4) Shift transmission into Reverse with brake applied. At
idle, pressure should be 112-130 psi (7.9-9.1 kg/cm
). Raise engine
RPM to stall speed (2100-2400 RPM). Note line pressure. Pressure
should be 227-285 psi (16.0-20.0 kg/cm
). If readings are not to

specification, use the following trouble shooting guide.
* Hydraulic Pressure High In All Ranges
Check throttle cable adjustment. If adjustment is okay, check
for throttle valve or regulator valve failure.
* Hydraulic Pressure Low In All Ranges
Check throttle cable adjustment. If adjustment is okay, check
for throttle valve, regulator valve, transmission oil pump or
overdrive clutch failure.
* Hydraulic Pressure Low In Drive Position
Check for fluid leaks in Drive hydraulic circuit. Check for
forward clutch or overdrive clutch failure.
* Hydraulic Pressure Low In Reverse Position
Check for fluid leaks in Reverse hydraulic circuit. Check for
transmission No. 3 brake failure, forward clutch failure or
overdrive clutch failure.
LINE PRESSURE (PICKUP)
1) Incorrect throttle pressure setting will cause incorrect
line pressure readings even though line pressure adjustment is
correct. Always inspect and correct throttle pressure adjustment
before adjusting line pressure.
2) Approximate adjustment, measured from valve body to inner
edge of adjusting nut, is 15/16". However, due to manufacturing
tolerances, adjustment can be varied to obtain correct line pressure.
3) Adjusting screw may be turned with an Allen wrench. One
complete turn of adjusting screw changes closed throttle line pressure
approximately 1 2/3 psi. Turn adjusting screw counterclockwise to
increase pressure or clockwise to decrease pressure.
THROTTLE PRESSURE (PICKUP)
1) Throttle pressures cannot be accurately tested. If a
malfunction exists, adjustment should be measured.
2) Insert Gauge Pin (C-3763) between throttle lever cam and
kickdown valve. Push in on tool to compress kickdown valve against its
spring.
3) As force is being exerted to compress spring, turn
throttle lever screw with Allen wrench until head of screw touches
throttle lever tang with gauge pin, and throttle valve bottoms. Ensure
adjustment is made with spring fully compressed and valve bottomed in
valve body.
KICKDOWN BAND
PICKUP
1) Locate kickdown band adjusting screw on left side of
transmission case. Loosen lock nut, and back off nut 5 turns. Ensure
adjusting screw turns freely in transmission case.
2) Using torque wrench, tighten adjusting screw to 72 INCH
lbs. (8 N.m). Back off adjusting screw 2 7/8 turns. Hold adjuster
screw in this position, and tighten lock nut to 30 ft. lbs. (41 N.m).
LOW-REVERSE BAND
PICKUP
1) Raise vehicle, drain transmission, and remove oil pan.
Loosen adjusting screw lock nut, and back off nut 5 turns. Ensure

adjusting screw turns freely in lever.
2) Using torque wrench, tighten band adjusting screw to 30
INCH lbs. (3.5 N.m). Back off adjusting screw 6 turns. Hold adjusting
screw in this position, and tighten lock nut to 25 ft. lbs. (34 N.m).
3) Reinstall oil pan using new gasket. Tighten pan bolts to
150 INCH lbs. (17 N.m). Refill with specified transmission fluid.
KICKDOWN SERVO
ECLIPSE, GALANT, MIRAGE, PRECIS & 3000GT
1) Remove all dirt and grease around kickdown servo switch.
Remove snap ring and kickdown servo switch.
2) To prevent servo piston from turning, install Adapter
(MD998915) and Kickdown Servo Wrench (MD998914) so tab of wrench
engages with notch of piston. See Fig. 2.
CAUTION: DO NOT push servo piston inward while installing adapter
and servo wrench. Install adapter in brake pressure port by
hand ONLY. DO NOT use wrench to tighten adapter.
Fig. 2: Adjusting Kickdown Servo (Except Montero & Pickup)
Courtesy of Mitsubishi Motor Sales of America.
3) Loosen lock nut to "V" channel of adjuster rod. See
Fig. 2 . Tighten inner section of Kickdown Service Adjustment Assembly
(MD998916) until it contacts lock nut.
4) Install outer section of kickdown service adjustment
assembly on lock nut. Rotate outer section to left and inner section
to right to contact lock nut with inner section.
5) Using an INCH lb. torque wrench on inner section, tighten
inner section to 86 INCH lbs. (9.8 N.m), and then loosen inner
section. Tighten inner section to 43 INCH lbs. (4.9 N.m).
CAUTION: Before tightening lock nut with torque wrench, tighten it
by hand until it contacts piston. If torque wrench is used

Fires With Key Flywheel runout contributes
released. Engine to the intermittent nature
Fires and Cranks
Normally









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AIR CONDITIONING & HEAT
AIR CONDITIONING TROUBLE SHOOTING
WARNING: This is GENERAL information. This article is not intended
to be specific to any unique situation or individual vehicle
configuration. The purpose of this Trouble Shooting
information is to provide a list of common causes to
problem symptoms. For model-specific Trouble Shooting,
refer to SUBJECT, DIAGNOSTIC, or TESTING articles available
in the section(s) you are accessing.
BASIC AIR CONDITIONING TROUBLE SHOOTING CHART









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CONDITION POSSIBLE CAUSE








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Compressor Not Working
Compressor clutch circuit open.

Compressor clutch coil inoperative.

Poor clutch ground connection.

Fan belts loose.

Thermostatic switch inoperative.

Thermostatic switch not adjusted.

Ambient temperature switch open.

Superheat fuse blown.








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Excessive Noise or Vibration
Missing or loose mounting bolts.

Bad idler pulley bearings.

Fan belts not tightened correctly.

Compressor clutch contacting body.

Excessive system pressure.

Compressor oil level low.

Damaged clutch bearings.

Damaged reed valves.

Damaged compressor.








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Insufficient or No Cooling;
Compressor Working
Expansion valve inoperative.

Heater control valve stuck open.

Low system pressure.

Blocked condenser fins.

Blocked evaporator fins.

Vacuum system leak.

Vacuum motors inoperative.

Control cables improperly adjusted.

Restricted air inlet.

Mode doors binding.

Blower motor inoperative.

Temperature above system capacity.








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HEATER SYSTEM TROUBLE SHOOTING
NOTE: This is GENERAL information. This article is not intended
to be specific to any unique situation or individual vehicle
configuration. The purpose of this Trouble Shooting
information is to provide a list of common causes to

BRAKE SYSTEM TROUBLE SHOOTING CHART








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CONDITION POSSIBLE CAUSE CORRECTION








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Brakes Pull Left
or Right Incorrect tire pressure Inflate tires to proper
pressure
Front end out of alignment See WHEEL ALIGNMENT
Mismatched tires Check tires sizes
Restricted brake lines
or hoses Check hose routing
Loose or malfunctioning
caliper See DISC BRAKES or
BRAKE SYSTEM
Bent shoe or oily linings See DRUM BRAKES or
BRAKE SYSTEM
Malfunctioning rear brakes See DRUM, DISC BRAKES
or BRAKE SYSTEM
Loose suspension parts See SUSPENSION









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Noises Without
Brakes Applied Front linings worn out Replace linings
Dust or oil on drums See DRUM, DISC BRAKES
or rotors or BRAKE SYSTEM









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Noises With
Brakes Applied Insulator on outboard See DISC BRAKES or
shoe damaged BRAKE SYSTEM
Incorrect pads or linings Replace pads or linings









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Brake Rough, Chatters
or Pulsates Excessive lateral runout Check rotor runout
Parallelism not to
specifications Reface or replace rotor
Wheel bearings not adjusted See SUSPENSION
Rear drums out-of-round Reface or replace drums
Disc pad reversed, steel
against rotor Remove and reinstall
pad









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Excessive Pedal
Effort Malfunctioning power unit See POWER BRAKES or
BRAKE SYSTEM
Partial system failure Check fluid and pipes
Worn disc pad or lining Replace pad or lining
Caliper piston stuck or

Incorrect ignition timing Reset ignition timing,
See TUNE-UP
Leaking valves Replace valves, See
ENGINES
Worn fuel pump diaphragm Replace diaphragm or
or piston piston









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Intake Backfire Improper ignition timing Reset ignition timing,
See TUNE-UP
Faulty accelerator pump Replace accelerator
discharge pump
Improper choke operation Check choke and adjust
as required
Defective EGR valve Replace EGR valve
Fuel mixture too lean Reset air/fuel mixture,
See TUNE-UP
Choke valve initial Reset choke valve
clearance too large initial clearance









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Exhaust Backfire Vacuum leak Inspect and repair
vacuum system
Faulty vacuum diverter Replace vacuum diverter
valve valve
Faulty choke operation Check choke and adjust
as required
Exhaust system leak repair exhaust system
leak









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Engine Ignition timing too far Reset ignition timing,
Detonation advanced See TUNE-UP
Faulty ignition system Check ignition timing,
See TUNE-UP
Spark plugs loose or Retighten or replace
faulty plugs
Fuel delivery system Inspect lines, pump and
clogged filter for clog
EGR valve inoperative Replace EGR valve
PCV system inoperative Inspect and/or replace
hoses or valve
Vacuum leaks Check vacuum system and
repair leaks
Excessive combustion
chamber deposits Remove built-up
deposits
Leaking, sticking or Inspect and/or replace
broken valves valves









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External Oil Fuel pump improperly seated Remove pump, replace
Leakage or worn gasket gasket and seat
properly
Oil pan gasket broken or Straighten pan and
pan bent replace gasket
Timing chain cover gasket Replace timing chain
broken cover gasket
Rear main oil seal worn Replace rear main oil
seal
Oil pan drain plug not Remove and reinstall
seated properly drain plug
Camshaft bearing drain Remove restriction
hole blocked
Oil pressure sending Remove and reinstall
switch leaking sending switch









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