1997 MITSUBISHI TRITON fuel

MPI ± Troubleshooting13A-32
INSPECTION PROCEDURE 11
When the engine is cold, it stalls at idling. (Die out)
Probable cause
In such cases as the above, the cause is probably that the air/fuel mixture is inappropriate
when the engine is cold, or that the intake air volume is insufficient.
Malfunction of the ISC servo system

Malfunction of the throttle body

Malfunction of the injector system

Malfunction of the ignition system
Were the battery terminals disconnected?Ye sAfter warming-up, let the engine run at idling for 10 minutes.
No
MUT-II Self-Diag code
Are diagnosis codes displayed?Ye sRefer to P.13A-10, INSPECTION CHART FOR DIAGNOSIS
CODES.
OK
Check the fuel pressure. (Refer to P.13A-81.)
OK
Check the ignition timing.
(Refer to GROUP 11 ± On-vehicle Service.)NGCheck that the distributor is installed properly.
OK
Check the following items.

Check the ignition coil, spark plugs, spark plug cables. (Refer to GROUP 16 ± On-vehicle Service.)

Check the compression pressure. (Refer to GROUP 11 ± On-vehicle Service.)

Check the engine oil viscosity.
OK
MUT-II Data list
26 Idle position switch (Refer to P.13A-57.)NGCheck the idle position switch system.
(Refer to P.13A-40, INSPECTION PROCEDURE 25.)
OK
Check the injector for operation sound.NGCheck the injector system. (Refer to P.13A-19, INSPECTION PRO-
CEDURE FOR DIAGNOSIS CODE 41.)
Ye s
Check the ISC servo for operation sound. (Refer to P.13A-90.)NGCheck the ISC servo system.
(Refer to P.13A-45, INSPECTION PROCEDURE 31.)
No
Is engine-idling stable after the warming-up?NoCheck if the unstable idling (Rough idling, hunting).
(Refer to P.13A-29, INSPECTION PROCEDURE 8.)
No
Does the engine stall right after the accelerator pedal is released?Ye sClean the throttle valve
area. (Refer to P.13A-78.)Check and adjust the
fixed SAS.
(Refer to P.13A-79.)
OK
MUT-II Data list
21 Engine coolant temperature sensor (Refer to P.13A-57.)NGCheck the engine coolant temperature sensor system.
(Refer to P.13A-14, INSPECTION PROCEDURE FOR DIAGNOSIS
CODE 21.)
OK
MUT-II Actuator test
10 EGR control solenoid valve (Refer to P.13A-62.)NGCheck the EGR control solenoid valve system. (Refer to P.13A-46,
INSPECTION PROCEDURE 33.)

MPI ± Troubleshooting13A-33
INSPECTION PROCEDURE 12
When the engine is hot, it stalls at idling. (Die out)
Probable cause
In such cases as the above, the cause is probably that ignition system, air/fuel mixture,
idle speed control (ISC) or compression pressure is defective.
In addition, if the engine suddenly stalls, the cause may also be a defective connector
contact.
Malfunction of the ignition system

Malfunction of air-fuel ratio control system

Malfunction of the ISC system

Drawing air into intake system

Improper connector contact
Were the battery terminals disconnected?Ye sAfter warming-up, let the engine run at idling for 10 minutes.
No
MUT-II Self-Diag code
Are diagnosis codes displayed?Ye sRefer to P.13A-10, INSPECTION CHART FOR DIAGNOSIS
CODES.
No
Check the ISC servo for operation sound. (Refer to P.13A-90.)NGCheck the ISC servo system.
(Refer to P.13A-45, INSPECTION PROCEDURE 31.)
OK
Check the injector for operation sound.NGCheck the injector system. (Refer to P.13A-19, INSPECTION PRO-
CEDURE FOR DIAGNOSIS CODE 41.)
OK
Does the engine stall right after the accelerator pedal is released?Ye sClean the throttle valve
area. (Refer to P.13A-78.)Check and adjust the
fixed SAS.
(Refer to P.13A-79.)
No
Does the engine stall easily again?NoWhile carrying out an intermittent malfunction simulation test (Refer
to GROUP 00 ± Points to Note for Intermittent Malfunctions.), check
for sudden changes in the signals shown below.

Crank angle sensor signal

Air flow sensor signal

Injector drive signal
Primary and secondary
ignition signal

Fuel pump drive signal

Engine-ECU power supply
voltage
Ye s
MUT-II: Engine stalling inspection when the engine is warm and
idling. (Refer to P.13A-50, INSPECTION PROCEDURE 39.)
OK
Check the ignition timing.
(Refer to GROUP 11 ± On-vehicle Service.)NGCheck that the distributor is installed properly.
OK
Check the following items.

Check the ignition coil, spark plugs, spark plug cables. (Refer to GROUP 16 ± On-vehicle Service.)

Check if the injectors are clogged.

Check the compression pressure. (Refer to GROUP 11 ± On-vehicle Service.)

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

MPI ± Troubleshooting13A-34
INSPECTION PROCEDURE 13
The engine stalls when starting the car. (Pass out)
Probable cause
In cases such as the above, the cause is probably misfiring due to a weak spark,
or an inappropriate air/fuel mixture when the accelerator pedal is depressed.
Drawing air into intake system

Malfunction of the ignition system
MUT-II Self-Diag code
Are diagnosis codes displayed?Ye sRefer to P.13A-10, INSPECTION CHART FOR DIAGNOSIS
CODES.
OK
Check the following items.

Check the ignition coil, spark plugs, spark plug cables. (Refer to GROUP 16 ± On-vehicle Service.)

Check if air was drawn into the intake system.
Broken intake manifold gasket
Broken or disconnected vacuum hose
Improper operation of the PCV valve
Broken air intake hose
No
MUT-II Actuator test
10 EGR control solenoid valve (Refer to P.13A-62.)NGCheck the EGR control solenoid valve system. (Refer to P.13A-46,
INSPECTION PROCEDURE 33.)
INSPECTION PROCEDURE 14
The engine stalls when decelerating.
Probable cause
In cases such as the above, the cause is probably that the intake air volume is insufficient
due to a defective idle speed control (ISC) servo system.
Malfunction of the ISC system
No
MUT-II Data list
26 Idle position switch (Refer to P.13A-69.)NGCheck the idle position switch system.
(Refer to P.13A-49, INSPECTION PROCEDURE 26.)
OK
MUT-II Data list
14 Throttle position sensor (Refer to P.13A-57.)NGCheck the throttle position sensor system. (Refer to P.13A-13, IN-
SPECTION PROCEDURE FOR DIAGNOSIS CODE 14.)
OK
MUT-II Data list
45 ISC servo position

Is the idle speed control (ISC) servo position drops to 0 ± 2
steps when decelerating (engine r/min less than 1,000)?Ye sCheck the vehicle speed sensor system. (Refer to P.13A-17, IN-
SPECTION PROCEDURE FOR DIAGNOSIS CODE 24.)
OK
Check the following items.

Check the ignition coil, spark plugs, spark plug cables. (Refer to GROUP 16 ± On-vehicle Service.)

Check the throttle valve area. (Refer to P.13A-78.)

Check and adjust the fixed SAS. (Refer to P.13A-79.)
No
MUT-II Data list
26 Idle position switch (Refer to P.13A-57.)NGCheck the idle position switch system.
(Refer to P.13A-40, INSPECTION PROCEDURE 25.)
No
MUT-II Actuator test
10 EGR control solenoid valve (Refer to P.13A-62.)NGCheck the EGR control solenoid valve system. (Refer to P.13A-46,
INSPECTION PROCEDURE 33.)
No
MUT-II Self-Diag code
Are diagnosis codes displayed?Ye sRefer to P.13A-10, INSPECTION CHART FOR DIAGNOSIS
CODES.
Were the battery terminals disconnected?Ye sAfter warming-up, let the engine run at idling for 10 minutes.

MPI ± Troubleshooting13A-35
INSPECTION PROCEDURE 15
Hesitation, sag or stumble
Probable cause
In cases such as the above, the cause is probably that ignition system, air/fuel mixture
or compression pressure is defective.
Malfunction of the ignition system

Malfunction of air-fuel ratio control system

Malfunction of the fuel supply system

Malfunction of the EGR control solenoid valve system

Poor compression
MUT-II Self-Diag code
Are diagnosis codes displayed?Ye sRefer to P.13A-10, INSPECTION CHART FOR DIAGNOSIS
CODES.
No
Check the injectors for operation sound.NGCheck the injector system. (Refer to P.13A-19, INSPECTION PRO-
CEDURE FOR DIAGNOSIS CODE 41.)
OK
Check the ignition timing.
(Refer to GROUP 11 ± On-vehicle Service.)NGCheck that the distributor is installed properly.
OK
MUT-II: Check if hesitation, sag, stumble or poor acceleration occur.
(Refer to P.13A-51, INSPECTION PROCEDURE 40.)
OK
Check the fuel pressure. (Refer to P.13A-81.)
OK
Check the following items.

Check the ignition coil, spark plugs, spark plug cables. (Refer to GROUP 16 ± On-vehicle Service.)

Check the EGR control system. (Refer to GROUP 17 ± Emission Control System.)

Check the compression pressure. (Refer to GROUP 11 ± On-vehicle Service.)

Check the fuel filter or fuel line for clogging.
INSPECTION PROCEDURE 16
The feeling of impact or vibration when accelerating
Probable cause
In cases such as the above, the cause is probably that there is an ignition leak
accompanying the increase in the spark plug demand voltage during acceleration.
Malfunction of the ignition system
MUT-II Self-Diag code
Are diagnosis codes displayed?Ye sRefer to P.13A-10, INSPECTION CHART FOR DIAGNOSIS
CODES.
No
Check the following items.

Check the ignition coil, spark plugs, spark plug cables. (Refer to GROUP 16 ± On-vehicle Service.)

Check for occurrence of ignition leak.

MPI ± Troubleshooting13A-36
INSPECTION PROCEDURE 17
The feeling of impact or vibration when decelerating.
Probable cause
Malfunction of the ISC system is suspected.
Malfunction of the ISC system
MUT-II Self-Diag code
Are diagnosis codes displayed?Ye sRefer to P.13A-10, INSPECTION CHART FOR DIAGNOSIS
CODES.
No
Check the ISC servo for operation sound. (Refer to P.13A-90.)NGCheck the ISC servo system.
(Refer to P.13A-45, INSPECTION PROCEDURE 31.)
OK
MUT-II Data list
14 Throttle position sensor (Refer to P.13A-57.)NGCheck the throttle position sensor system. (Refer to P.13A-13, IN-
SPECTION PROCEDURE FOR DIAGNOSIS CODE 14.)
OK
MUT-II Data list
26 Idle position switch (Refer to P.13A-57.)NGCheck the idle position switch system.
(Refer to P.13A-40, INSPECTION PROCEDURE 25.)
OK
Clean the throttle valve area. (Refer to P.13A-78.)
INSPECTION PROCEDURE 18
Poor acceleration
Probable cause
Defective ignition system, abnormal air-fuel ratio, poor compression pressure, etc.
are suspected.
Malfunction of the ignition system

Malfunction of air-fuel ratio control system

Malfunction of the fuel supply system

Poor compression pressure

Clogged exhaust system
MUT-II Self-Diag code
Are diagnosis codes displayed?Ye sRefer to P.13A-10, INSPECTION CHART FOR DIAGNOSIS
CODES.
No
Check the injectors for operation sound.NGCheck the injector system. (Refer to P.13A-19, INSPECTION PRO-
CEDURE FOR DIAGNOSIS CODE 41.)
OK
Check the ignition timing.
(Refer to GROUP 11 ± On-vehicle Service.)NGCheck that the distributor is installed properly.
OK
MUT-II: Check if hesitation, sag, stumble or poor acceleration occur.
(Refer to P.13A-51, INSPECTION PROCEDURE 40.)
OK
Check the fuel pressure. (Refer to P.13A-81.)
OK
Check the following items.

Check the ignition coil, spark plugs, spark plug cables. (Refer to GROUP 16 ± On-vehicle Service.)

Check the compression pressure. (Refer to GROUP 11 ± On-vehicle Service.)

Check the fuel filter or fuel line for clogging.

Broken air intake hose

Clogged air cleaner

MPI ± Troubleshooting13A-37
INSPECTION PROCEDURE 19
Surge
Probable cause
Defective ignition system, abnormal air-fuel ratio, etc. are suspected.
Malfunction of the ignition system

Malfunction of air-fuel ratio control system

Malfunction of the EGR control solenoid valve system
MUT-II Self-Diag code
Are diagnosis codes displayed?Ye sRefer to P.13A-10, INSPECTION CHART FOR DIAGNOSIS
CODES.
No
Check the injectors for operation sound.NGCheck the injector system. (Refer to P.13A-19, INSPECTION PRO-
CEDURE FOR DIAGNOSIS CODE 41.)
OK
Check the ignition timing.
(Refer to GROUP 11 ± On-vehicle Service.)NGCheck that the distributor is installed properly.
OK
MUT-II: Check if surge occurs.
(Refer to P.13-52, INSPECTION PROCEDURE 41.)
OK
Check the fuel pressure. (Refer to P.13A-81.)
OK
Check the following items.

Check the ignition coil, spark plugs, spark plug cables. (Refer to GROUP 16 ± On-vehicle Service.)

Check the EGR control system. (Refer to GROUP 17 ± Emission Control System.)
INSPECTION PROCEDURE 20
Knocking
Probable cause
In cases as the above, the cause is probably that the heat value of the spark plug
is inappropriate.
Inappropriate heat value of the spark plug
Check the following items.

Spark plugs

Check if foreign materials (water, alcohol, etc.) got into fuel.
INSPECTION PROCEDURE 21
Dieseling
Probable cause
Fuel leakage from injectors is suspected.
Fuel leakage from injectors
Check the injectors for fuel leakage.

MPI ± Troubleshooting13A-38
INSPECTION PROCEDURE 22
Too high CO and HC concentration when idling
Probable cause
Abnormal air-fuel ratio is suspected.
Malfunction of the air-fuel ratio control system

Deteriorated catalyst
Check trouble symptom.
No
Check the ignition timing.
(Refer to GROUP 11 ± On-vehicle Service.)NGCheck that the distributor is installed properly.
OK
MUT-II Data list
21 Engine coolant temperature sensor. (Refer to P.13A-57.)NGCheck the engine coolant temperature sensor system.
(Refer to P.13A-14, INSPECTION PROCEDURE FOR DIAGNOSIS
CODE 21.)
OK
MUT-II Data list
13 Intake air temperature sensor (Refer to P.13A-57.)NGCheck the intake air temperature sensor system. (Refer to P.13A-12,
INSPECTION PROCEDURE FOR DIAGNOSIS CODE 13.)
OK
MUT-II Data list
25 Barometric pressure sensor (Refer to P.13A-57.)NGCheck the barometric pressure sensor system. (Refer to P.13A-18,
INSPECTION PROCEDURE FOR DIAGNOSIS CODE 25.)
OK
MUT-II Data list
11 Oxygen sensor
OK:600 ± 1,000 mV when racing suddenly (Refer to P.13A-57.)NGCheck the oxygen sensor system. (Refer to P.13A-11, INSPECTION
PROCEDURE FOR DIAGNOSIS CODE 11.)
OK
MUT-II Data list
11 Oxygen sensor
OK:Repeat 0 ± 400 mV and 600 ± 1,000 mV alternately when
idling. (Refer to P.13A-57.)OK
NG
Check the fuel pressure. (Refer to P.13A-81.)
OK
NG
Check the following items.

Check the injectors for operation sound.

Check the injectors for fuel leakage.

Check the ignition coil, spark plugs, spark plug cables. (Refer to GROUP 16 ± On-vehicle Service.)

Check the compression pressure. (Refer to GROUP 11 ± On-vehicle Service.)

Check the positive crankcase ventilation system. (Refer to GROUP 17 ± Emission Control System.)

Check the purge control system. (Refer to GROUP 17 ± Emission Control System.)

Check the EGR control system. (Refer to GROUP 17 ± Emission Control System.)
Check the trouble symptom.
NG
Replace the catalytic converter.
Replace the oxygen sensor.
MUT-II Self-Diag code
Are diagnosis codes displayed?Ye sRefer to P.13A-10, INSPECTION CHART FOR DIAGNOSIS
CODES.

MPI ± Troubleshooting13A-40
INSPECTION PROCEDURE 24
Fuel pump system
Probable cause
The engine-ECU turns the control relay ON when the engine is cranking or running,
and this supplies power to drive the fuel pump.
Malfunction of the fuel pump relay

Malfunction of the fuel pump

Improper connector contact, open circuit or
short-circuited harness wire

Malfunction of the engine-ECU
Check the fuel pump operation. (Refer to P.13A-84.)NGCheck the fuel pump circuit.
(Refer to P.13A-53, INSPECTION PROCEDURE 43.)
OK
Check the fuel pump relay. (Refer to P.13A-86.)NG
Replace
OK
Measure at the fuel pump relay connector C-54.

Connect the connector.

Voltage between 1 and earth

MUT-II Actuator test: Fuel pump drive
OK:System voltageNGCheck the fuel pump drive control circuit.
(Refer to P.13A-54, INSPECTION PROCEDURE 44.)
OK
Check the harness wire between fuel pump relay connector and
fuel pump drive terminal, and repair if necessary.
INSPECTION PROCEDURE 25
Idle position switch system
Probable cause
The idle position switch inputs the condition of the accelerator pedal, i.e. whether
it is depressed or released (HIGH/LOW), to the engine-ECU.
The engine-ECU controls the idle speed control servo based on this input.
Maladjustment of the accelerator pedal

Maladjustment of the fixed SAS

Maladjustment of the idle position switch and throttle
position sensor

Improper connector contact, open circuit or
short-circuited harness wire

Malfunction of the engine-ECU
Check the idle position switch. (Refer to P.13A-87.)NGReplace
OK
Measure at the throttle position sensor connector A-47.

Disconnect the connector, and measure at the harness side.

Voltage between 2 and earth (Ignition switch: ON)
OK:4 V or higher

Continuity between 1 and earth
OK:ContinuityNGCheck the following
connector. C-51NG
Repair
OK
Check trouble symptom.
NG
Check the harness wire between engine-ECU and throttle position
sensor connector.
OK
Replace the engine-ECU.
NG
Repair
OK
Check the following
connector. A-47NG
Repair
OK
Check trouble symptom.
NG
Replace the engine-ECU.