Mitsubishi Montero (2004+). Manual - part 414

EMISSION CONTROL

TSB Revision

ENGINE AND EMISSION CONTROL

17-63

VACUUM HOSE CHECK

M1173007300171

1. Using the VACUUM HOSE ROUTING diagram as a guide, 

check that the vacuum hoses are correctly connected.

2. Check the connection of the vacuum hoses, (removed, 

loose, etc.) and confirm that there are no sharp bends or 
damage.

POSITIVE CRANKCASE VENTILATION SYSTEM

GENERAL DESCRIPTION (POSITIVE CRANKCASE VENTILATION SYSTEM)

M1173005000301

The positive crankcase ventilation (PCV) system pre-
vents the escape of blow-by gases from inside the 
crankcase into the atmosphere.
Fresh air is sent from the cleaner into the crankcase 
through the breather hose to be mixed with the 
blow-by gas inside the crankcase.
The blow-by gas inside the crankcase is drawn into 
the intake manifold through the PCV valve.

The PCV valve is designed to lift the plunger accord-
ing to the intake manifold vacuum so as to regulate 
the flow of blow-by gas properly.
In other words, the blow-by gas flow is regulated dur-
ing low load engine operation to maintain engine sta-
bility, while the flow is increased during high load 
operation to improve the ventilation performance.

SYSTEM DIAGRAM

AK301587

VENTILATION HOSE

BREATHER HOSE

POSITIVE CRANKCASE
VENTILATION VALVE

AB

EMISSION CONTROL

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ENGINE AND EMISSION CONTROL

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COMPONENT LOCATION

M1173007400190

POSITIVE CRANKCASE VENTILATION SYSTEM 
CHECK

M1173001100232

1. Remove the positive crankcase ventilation (PCV) valve from 

the rocker cover, then reconnect the PCV valve to the 
vacuum supply hose.

2. With the engine idling, put your finger on the open end of the 

PCV valve, and check for negative pressure (vacuum).
NOTE: At this time, the plunger in the PCV valve should 
move back and forth as the open end is covered and uncov-
ered.

3. If negative pressure is not felt, clean or replace the PCV 

valve. Inspect the vacuum supply hose and vacuum supply 
hose port for restriction or plugged condition.

POSITIVE CRANKCASE VENTILATION VALVE 
CHECK

M1173001200228

1. Hold the positive crankcase ventilation (PCV) valve with the 

vacuum side down. Insert a thin rod, and using light 
pressure, depress the end of the PCV valve spring by 5 

− 10 

mm (0.2 

− 0.3 inch). Release pressure on the rod to see if 

the PCV valve spring will lift the rod to its original position. 

2. If the rod returns quickly to its original position, the PCV 

valve is OK. If the stick does not return quickly, clean or 
replace the PCV valve.

EVAPORATIVE EMISSION CONTROL SYSTEM

GENERAL DESCRIPTION (EVAPORATIVE EMISSION SYSTEM)

M1173005100397

The evaporative emission (EVAP) system prevents 
fuel vapors generated in the fuel tank from escaping 
into the atmosphere. Fuel vapors from the fuel tank 
flows through the fuel tank pressure control valve 
and vapor pipe/hose to be stored temporarily in the 

EVAP canister. When the vehicle is in operation, fuel 
vapors stored in the EVAP canister flow through the 
EVAP purge solenoid, purge port and intake manifold 
plenum to the combustion chamber. When the 
engine coolant temperature is low or when the intake 

AK301590

POSITIVE CRANKCASE VENTILATION VALVE

AB

AK203692

POSITIVE CRANKCASE
VENTILATION VALVE

AC

AK301831

5 – 10 mm

(0.2 – 0.3 in)

THIN ROD
(VERY SMOOTH)

POSITIVE 
CRANKCASE 
VENTILATION 
VALVE

VACUUM SIDE

AB

EMISSION CONTROL

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ENGINE AND EMISSION CONTROL

17-65

air quantity is small (when the engine is at idle, for 
example), the PCM brings the EVAP purge solenoid 
into the OFF state to shut off the fuel vapor flow to 
the intake manifold plenum. This ensures the 
driveability when the engine is cold or running under 
low load and also stabilizes the emission level. An 
EVAP ventilation solenoid is provided between the 
EVAP canister and atmosphere, and used to monitor 
for OBD-II EVAP leaks. This solenoid is normally 

OFF. However, it turns ON when monitoring the 
OBD-II EVAP leaks and shuts off the atmosphere 
flow to the EVAP canister. Then the fuel tank differ-
ential pressure sensor monitors the fuel vapor pres-
sure to detect OBD-II EVAP leaks. The fuel overflow 
limiter valve prevent fuel from being overfilled. The 
fuel cut off valve prevents fuel leaks if the vehicle is 
rolled over in an accident.

SYSTEM DIAGRAM

COMPONENT LOCATION

M1173007500261

AK301591

FUEL TANK DIFFERENTIAL
PRESSURE SENSOR

LIQUID SEPARATOR

EVAPORATIVE
EMISSION 
CANISTER

EVAPORATIVE EMISSION 
PURGE SOLENOID 
ON: OPEN

PCM

BAROMETRIC PRESSURE 
SENSOR

INTAKE AIR TEMPERATURE
SENSOR

ENGINE COOLANT 
TEMPERATURE SENSOR

VOLUME AIRFLOW SENSOR

FUEL
TANK

MFI 
RELAY

FUEL OVERFLOW 
LIMITER VALVE 

FUEL CUT
OFF VALVE

LEVELING VALVE

EVAPORATIVE EMISSION 
VENTILATION 
SOLENOID VALVE

AIR FILTER

EVAPORATIVE EMISSION 
VENTILATION SOLENOID
ON: CLOSED

AB

AK303225

AB

EVAPORATIVE EMISSION PURGE SOLENOID

AK303224AB

EVAPORATIVE EMISSION VENTILATION
SOLENOID

EMISSION CONTROL

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ENGINE AND EMISSION CONTROL

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PURGE CONTROL SYSTEM CHECK (PURGE FLOW CHECK)

M1173001400288

Required Special Tool:
MB995061: Purge Flow Indicator
1. Disconnect the purge hose from the evaporative emission 

(EVAP) purge solenoid, and connect the special tool 
MB995061 between the EVAP purge solenoid and the purge 
hose.

2. Before checks, set the vehicle in the following conditions:

• Engine coolant temperature: 80 − 95°C (176 − 203°F)

• Lights and accessories: OFF

• Transmission: P range

NOTE: Vehicles for Canada, the headlight, taillight, etc. 
remain lit even when the lighting switch is in "OFF" position 
but this is no problem for checks.

3. Run the engine at idle for more than four minutes.
4. Check the purge flow volume when the engine is revved 

several times.

Standard value: Momentarily 20 cm

3

/sec. (2.5 SCFH) or 

more.

AK300654

THROTTLE BODY

INTAKE MANIFOLD

FROM 
AIR CLEANER

TO 
COMBUSTION
CHAMBER

OFF

ON

EVAPORATIVE EMISSION
PURGE SOLENOID
(ON: OPENED)

PURGE
FLOW
INDICATOR
(MB995061)

PURGE HOSE

EVAPORATIVE EMISSION
CANISTER

AB