Mitsubishi Evolution X. Manual - part 226

EMISSION CONTROL <MFI - T/C>

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ENGINE AND EMISSION CONTROL

17-73

COMPONENT LOCATION

M1173007400833

AK703198AD

Positive crankcase
ventilation valve

POSITIVE CRANKCASE VENTILATION (PCV) 
SYSTEM CHECK

M1173001100878

1. Remove the ventilation hose from the positive crankcase 

ventilation (PCV) valve.

2. Remove the PCV valve from the rocker cover.
3. Reinstall the PCV valve at the ventilation hose.
4. Start the engine and run at idle.

AK604163

Positive crankcase 
ventilation valve

AB

5. Place a finger at the opening of the PCV valve and check 

that vacuum of the intake manifold is felt.
NOTE: At this moment, the plunger in the PCV valve moves 
back and forth.

6. If vacuum is not felt, clean the PCV valve or replace it.
7. Apply a small amount of new engine oil to the O-ring on the 

PCV valve, and tighten to the specified torque. 

Standard value: 2.5 

± 0.4 N⋅ m (22 in-lb)

POSITIVE CRANKCASE VENTILATION (PCV) 
SYSTEM CHECK

M1173001200808

1. Remove the ventilation hose from the positive crankcase 

ventilation (PCV) valve.

2. Remove the PCV valve from the rocker cover.

AK604164

Positive crankcase 
ventilation valve

Thin rod 
(very smooth)

5 10 mm

(0.2 0.3 in)

Vacuum side

AB

3. Hold the 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.

4. 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.

5. Apply a small amount of new engine oil to the O-ring on the 

PCV valve, and tighten to the specified torque. 

Standard value: 2.5 

± 0.4 N⋅ m (22 in-lb)

EMISSION CONTROL <MFI - T/C>

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ENGINE AND EMISSION CONTROL

17-74

EVAPORATIVE EMISSION CONTROL SYSTEM

GENERAL INFORMATION (EVAPORATIVE EMISSION SYSTEM)

M1173005101389

The evaporative emission (EVAP) system prevents 
fuel vapors generated in the fuel tank from escaping 
into the atmosphere.
Fuel vapors from the fuel tank flow through the vapor 
pipe/hose to be stored temporarily in the EVAP can-
ister.
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 air quantity is small (when the engine is at 
idle, for example), the engine control module (ECM) 
brings the EVAP purge solenoid into the OFF state to 
shut off the fuel vapor flow to the intake manifold ple-
num. This ensures 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 to monitor for 
OBD-II EVAP leaks. This solenoid is normally OFF. 
However, it turns ON when monitoring for OBD-II 
EVAP leaks and shuts off the atmosphere flow to the 
EVAP canister. Then the fuel tank differential pres-
sure sensor monitors the fuel vapor pressure to 
detect OBD-II EVAP leaks. The fuel overflow limiter 
valve and the leveling valve prevent fuel from being 
overfilled. The fuel overflow limiter valve and the lev-
eling valve prevents fuel leaks if the vehicle is rolled 
over in an accident.
The EVAP ventilation valve releases the air from the 
fuel tank through the EVAP canister into the atmo-
sphere when the fuel tank pressure increases due to 
refueling, etc. The EVAP ventilation valve and the air 
filter supply the atmospheric air to the EVAP canister 
when the fuel tank pressure decreases. 

EMISSION CONTROL <MFI - T/C>

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ENGINE AND EMISSION CONTROL

17-75

SYSTEM DIAGRAM

AK704215

Evaporative emission
purge solenoid

Battery

Check valve

ECU

Mass airflow sensor

Throttle position sensor

No. 1 intake air
temperature sensor

Barometric
pressure sensor

Engine coolant
temperature sensor

Crankshaft position
sensor

AB

Evaporative emission 
ventilation solenoid 

Evaporative
emission canister

From fuel tank

EMISSION CONTROL <MFI - T/C>

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ENGINE AND EMISSION CONTROL

17-76

COMPONENT LOCATION

M1173007500788

AK704216

AB

Evaporative emission
purge solenoid

AK704641

AB

Evaporative emission 
ventilation solenoid

Fuel vapor
canister
assembly

PURGE CONTROL SYSTEM CHECK (PURGE FLOW CHECK)

M1173001401258

AK704217AB

Intake manifold
plenum

Throttle body

To combustion
chamber

Check valve

From
air
cleaner

OFF

ON

Purge
flow
indicator
(MB995061)

Purge hose

Evaporative 
emission 
purge 
solenoid
(ON: open)

Evaporative
emission
canister

Required Special Tool:

• MB995061: Purge Flow Indicator

1. Disconnect the purge hose from the evaporative emission 

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