Mitsubishi Lancer Evolution VI. Manual - part 34

MPI  – 

Troubleshooting

13-24

INSPECTION PROCEDURE 7

Long time to start (Improper starting)

Probable cause

In cases such as the above, the cause is probably that the spark is weak and ignition
is difficult, the initial mixture for starting is not appropriate, or sufficient compression
pressure is not being obtained.

D

Malfunction of the ignition system

D

Malfunction of the injector system

D

Inappropriate gasoline use

D

Poor compression

Check system voltage when cranking

OK: 8 V or higher

NG

Check the battery.

OK

MUT-

II

: Check if uncomplete combustion occurs. 

(Refer to P.13-48, INSPECTION PROCEDURE 39.)

OK

Can any sound be heard from the injectors when cranking (check
using a soundscope)?

NG

Check the injector system. (Refer to P.13-15, INSPECTION PRO-
CEDURE FOR DIAGNOSIS CODE 41.)

OK

Check the ignition timing when cranking.

OK: Approx. 5

_

BTDC

NG

Check that the crank angle sensor and the timing belt cover are
installed properly.

OK

Check the following items.

D

Check the ignition coil, spark plugs, spark plug cables.

D

Check the injectors for clogging and leakage.

D

Check the compression pressure.

D

Check if foreign materials (water, alcohol, etc.) got into fuel.

MPI  – 

Troubleshooting

13-25

INSPECTION PROCEDURE 8

Unstable idling (Rough idling, hunting)

Probable cause

In cases as the above, the cause is probably that the ignition system, air/fuel mixture,
idle speed control (ISC) or compression pressure is defective.
Because the range of possible causes is broad, inspection is narrowed down to simple
items.

D

Malfunction of the ignition system

D

Malfunction of air-fuel ratio control system

D

Malfunction of the ISC servo system

D

Poor compression

D

Drawing air into exhaust system

D

Secondary air backflow to the intake system

Were the battery terminals disconnected recently?

Yes

After warming-up, let the engine run at idling for about 10 minutes.

No

MUT-

II

 Self-Diag code

Are diagnosis codes displayed?

Yes

Refer to P.13-8, INSPECTION CHART FOR DIAGNOSIS CODES.

No

Does idling speed fluctuate excessively?

Yes

Check if hunting occurs. 
(Refer to P.13-48, INSPECTION PROCEDURE 40.)

No

Check the ISC servo for operation sound.

NG

Check the ISC servo system.
(Refer to P.13-44, INSPECTION PROCEDURE 33.)

OK

Check the injector for operation.

NG

Check the injector system. (Refer to P.13-15, INSPECTION PRO-
CEDURE FOR DIAGNOSIS CODE 41.)

OK

MUT-

II

: Check if idling speed is unstable. 

(Refer to P.13-49, INSPECTION PROCEDURE 41.)

OK

Check the ignition timing. 
(Refer to GROUP 11 – Engine Adjustment.)*

NG

Check that the crank angle sensor and the timing belt cover are
installed properly.

OK

Check the following items.

D

Check the ignition coil, spark plugs, spark plug cables.

D

Check the secondary air supply system. (Ensure that there is no back flow of secondary air into the intake system.)

D

Check the compression pressure.

D

Check if foreign materials (water, alcohol, etc.) got into fuel.

NOTE
*:

Refer to Workshop Manual for LANCER EVOLUTION-IV and EVOLUTION-V (Pub. No. S9806CNCP9).

MPI  – 

Troubleshooting

13-26

INSPECTION PROCEDURE 9

Idling speed is high. (Improper idling speed)

Probable cause

In such cases as the above, the cause is probably that the intake air volume during
idling is too great.

D

Malfunction of the ISC servo system

D

Malfunction of the throttle body

OK

MUT-

II

 Data list

26 Idle position switch (Refer to P.13-58.)

NG

Check the idle position switch system.
(Refer to P.13-38, INSPECTION PROCEDURE 26.)

No

Check the ISC servo for operation sound.

NG

Check the ISC servo system.
(Refer to P.13-44, INSPECTION PROCEDURE 33.)

OK

MUT-

II

 Data list

21 Engine coolant temperature sensor (Refer to P.13-57.)

NG

Check the engine coolant temperature sensor system. 
(Refer to P.13-10, INSPECTION PROCEDURE FOR DIAGNOSIS
CODE 21.)

OK

MUT-

II

 Data list

28 A/C switch (Refer to P.13-58.)

NG

Check the A/C switch and A/C relay system. 
(Refer to P.13-39, INSPECTION PROCEDURE 29.)

OK

Basic idle speed adjustment (Refer to P.13-30.)*

Check trouble symptom.

NG

Clean the throttle valve area.

Adjust the fixed SAS. (Refer to P.13-30.)*

MUT-

II

 Self-Diag code

Are diagnosis codes displayed?

Yes

Refer to P.13-8, INSPECTION CHART FOR DIAGNOSIS CODES.

NOTE
*:

Refer to Workshop Manual for LANCER EVOLUTION-IV and EVOLUTION-V (Pub. No. S9806CNCP9).

MPI  – 

Troubleshooting

13-27

INSPECTION PROCEDURE 10

Idling speed is low. (Improper idling speed)

Probable cause

In cases such as the above, the cause is probably that the intake air volume during
idling is too small.

D

Malfunction of the ISC servo system

D

Malfunction of the throttle body

MUT-

II

 Self-Diag code

Are diagnosis codes displayed?

Yes

Refer to P.13-8, INSPECTION CHART FOR DIAGNOSIS CODES.

No

Check the ISC servo for operation sound.

NG

Check the ISC servo system.
(Refer to P.13-44, INSPECTION PROCEDURE 33.)

OK

MUT-

II

 Data list

26 Idle position switch (Refer to P.13-58.)

NG

Check the idle position switch system.
(Refer to P.13-38, INSPECTION PROCEDURE 26.)

OK

MUT-

II

 Data list

21 Engine coolant temperature sensor (Refer to P.13-57.)

NG

Check the engine coolant temperature sensor system. 
(Refer to P.13-10, INSPECTION PROCEDURE FOR DIAGNOSIS
CODE 21.)

OK

Basic idle speed adjustment (Refer to P.13-30.)*

Check trouble symptom.

NG

Clean the throttle valve area.

Adjust the fixed SAS. (Refer to P.13-30.)*

NOTE
*:

Refer to Workshop Manual for LANCER EVOLUTION-IV and EVOLUTION-V (Pub. No. S9806CNCP9).