Mitsubishi Lancer. Manual - part 215

EMISSION CONTROL <MPI>

ENGINE AND EMISSION CONTROL

17-8

VACUUM HOSE INSTALLATION

M1173007200107

1. When connecting the vacuum hoses, they should 

be securely inserted onto the nipples.

2. Connect the hoses correctly, using the vacuum 

hose piping diagram as a guide.

CRANKCASE EMISSION CONTROL 
SYSTEM

GENERAL INFORMATION (CRANKCASE 
EMISSION CONTROL SYSTEM)

M1173005000237

The crankcase emission control system prevents 
blow-by gases from escaping inside the crankcase 
into the atmosphere.

Fresh air is sent from the air cleaner into the crank-
case through the breather hose.
The air becomes mixed with the blow-by gases 
inside the crankcase.
The blow-by gas inside the crankcase is drawn into 
the intake manifold through the positive crankcase 
ventilation (PCV) valve.
The PCV valve lifts the plunger according 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

AK204365

Air cleaner

Air

Ventilation hose

Breather hose

PCV valve

AB

EMISSION CONTROL <MPI>

ENGINE AND EMISSION CONTROL

17-9

COMPONENT LOCATION (CRANKCASE 
EMISSION CONTROL SYSTEM)

M1173007400208

AK300767

<4G1>

AB

PCV valve

AK204366

<4G6>

AC

PCV valve

POSITIVE CRANKCASE VENTILATION 
SYSTEM CHECK

M1173001100179

1. Remove the ventilation hose from the 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.

AKX00336

PCV valve

AD

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.

POSITIVE CRANKCASE VENTILATION 
(PCV) VALVE CHECK

M1173001200187

AK100010

PCV valve

AC

1. Insert a thin rod into the PCV valve from the side 

shown in the illustration (rocker cover installation 
side), and move the rod back and forth to check 
that the plunger moves.

2. If the plunger does not move, there is a clogging 

in the PCV valve. In this case, clean or replace 
the PCV valve.

EVAPORATIVE EMISSION CONTROL 
SYSTEM

GENERAL INFORMATION (EVAPORATIVE 
EMISSION CONTROL SYSTEM)

M1173005100405

The evaporative emission control system prevents 
fuel vapours generated in the fuel tank from escaping 
into the atmosphere.
Fuel vapours from the fuel tank flow through the fuel 
tank pressure control valve and vapour pipe/hose to 
be stored temporarily in the canister.
When driving the vehicle, fuel vapours stored in the 
canister flow through the purge solenoid and purge 
port and go into the intake manifold to be sent 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 unit turns the 
purge solenoid off to shut off the fuel vapour flow to 
the intake manifold.
This does not only insure the driveability when the 
engine is cold or running under low load but also sta-
bilize the emission level.

EMISSION CONTROL <MPI>

ENGINE AND EMISSION CONTROL

17-10

SYSTEM DIAGRAM

AK204367AC

Throttle body

Canister

From
fuel
tank

OFF

ON

Purge
control
solenoid
valve

Control
relay

Battery

Engine-ECU <4G1-M/T, 4G6>,
Engine-A/T-ECU <4G1-A/T>

Air flow sensor <4G6>

Engine coolant
temperature sensor

Intake air
temperature sensor

Barometric pressure
sensor <4G6>

Manifold absolute pressure 
(MAP) sensor <4G1>

COMPONENT LOCATION (EVAPORATIVE 
EMISSION CONTROL SYSTEM) 

M1173007500216

AK300769

<4G1>

AB

Purge control
solenoid valve

AK300770

<4G6>

AB

Purge control
solenoid valve

PURGE CONTROL SYSTEM CHECK

M1173001400299

AK300771

<4G1>

AB

Plug

Vacuum hose

AK300772

<4G6>

AB

Plug

Vacuum hose

1. Disconnect the vacuum hose (red stripe) from 

throttle body and connect it to a hand vacuum 
pump.

EMISSION CONTROL <MPI>

ENGINE AND EMISSION CONTROL

17-11

2. Plug the nipple from which the vacuum hose was 

removed.

3. When the engine is cold or hot, apply a vacuum of 

53 kPa, and check the condition of the vacuum.

When engine is cold 

 

(Engine coolant temperature: 40

° C or less)

Engine condition

Normal condition

At idle

Vacuum is maintained.

3,000 r/min

When engine is hot 

 

(Engine coolant temperature: 80

° C or higher)

Engine condition

Normal condition

At idle

Vacuum is maintained.

3,000 r/min (within 3 
minutes after engine 
starts)

Vacuum will leak.

PURGE PORT VACUUM CHECK

M1173001500177

AK300773

<4G1>

AB

Plug

Vacuum hose

AK300774

<4G6>

AB

Plug

Vacuum hose

1. Disconnect the vacuum hose (red stripe) from the 

throttle body and connect a hand vacuum pump to 
the nipple.

2. Plug the vacuum hose (red stripe).

AK100011

AC

Vac-
uum

Engine speed (r/min)

3. Start the engine.
4. Check that a fairly constant negative pressure is 

generated regardless of the engine speed.

5. If no negative pressure is generated, the port is 

probably blocked and should be cleaned.

PURGE CONTROL SOLENOID VALVE 
CHECK

M1173001700193

NOTE: When disconnecting the vacuum hose, 
always make a mark so that it can be reconnected at 
original position.

AK100012 AC

Battery

A

AK100013

1. Disconnect the vacuum hose from the solenoid 

valve.

2. Disconnect the harness connector.
3. Connect a hand vacuum pump to nipple (A) of the 

solenoid valve (refer to the illustration at left).

4. Check airtightness by applying a vacuum with 

voltage applied directly from the battery to the 
purge control solenoid valve and without applying 
voltage.