1997 MITSUBISHI TRITON engine coolant

MPI ± Troubleshooting13A-31
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.
Malfunction of the ISC servo system

Malfunction of the throttle body
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
26 Idle position switch (Refer to P.13A-57.)NGCheck the idle position switch system.
(Refer to P.13A-40, INSPECTION PROCEDURE 25.)
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
29 Inhibitor switch (Refer to P.13A-57.)NGCheck the ignition switch ST and inhibitor switch system .
(Refer to P.13A-42, INSPECTION PROCEDURE 27.)
OK
Basic idle adjustment (Refer to P.13A-79.)
Check trouble symptom.NGClean the throttle valve area. (Refer to P.13A-78.)
Check and adjust the fixed SAS. (Refer to P.13A-79.)

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-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-47
INSPECTION PROCEDURE 34
MUT-II: Inspection of no initial combustion
MUT-II Data list
16 Voltage of engine-ECU power source (Refer to P.13A-57.)NGCheck the power supply and ignition switch-IG system.
(Refer to P.13A-39, INSPECTION PROCEDURE 23.)
OK
Does the camshaft rotate at the engine cranking?
(When oil filler cap is removed.)NoCheck timing belt for breakage.
Ye s
MUT-II Self-Diag code
Are diagnosis codes displayed?Ye sRefer to P.13A-10, INSPECTION CHART FOR DIAGNOSIS
CODES.
No
MUT-II Data list
22 Crank angle sensor
OK:Cranking speed is displayed.NoCheck the crank angle sensor system.
(Refer to P.13A-15, INSPECTION PROCEDURE FOR DIAGNOSIS
CODE 22.)
OK
MUT-II Actuator test
07 Fuel pump (Refer to P.13A-62.)NGCheck the fuel pump system.
(Refer to P.13A-40, INSPECTION PROCEDURE 24.)
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.)
INSPECTION PROCEDURE 35
Ignition system: Inspection of no initial combustion.
Does the engine tachometer display the cranking speed?

Set the tachometer of primary voltage detection type.NGCheck ignition circuit system.
(Refer to P.13A-44, INSPECTION PROCEDURE 30.)
OK
Check the ignition timing when cranking.
OK:Approx. 5BTDCNGCheck that the crank angle sensor is installed properly.

MPI ± Troubleshooting13A-48
INSPECTION PROCEDURE 36
MUT-II: Check if uncomplete combustion occurs.
MUT-II Self-Diag code
Are diagnosis codes displayed?Ye sRefer to P.13A-10, INSPECTION CHART FOR DIAGNOSIS CODE
No
MUT-II Actuator test
07 Fuel pump (Refer to P.13A-62.)NGCheck the fuel pump system.
(Refer to P.13A-40, INSPECTION PROCEDURE 24.)
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 PROCEDURES FOR DIAGNO-
SIS CODE 21.)
OK
MUT-II Data list
18 Ignition switch-ST (Refer to P.13A-57.)NGCheck the ignition switch-ST system .
(Refer to P.13A-41, INSPECTION PROCEDURE 26.)
INSPECTION PROCEDURE 37
Check if hunting occurs.
Clean the throttle body. (Refer to P.13A-78.)
Check and adjust the fixed SAS. (Refer to P.13A-79.)
Check trouble symptom.
NG
Inspect the intake of air into the air intake system

Broken intake manifold gasket

Broken air intake hose

Broken vacuum hose

Positive crankcase ventilation valve does not operate.

MPI ± Troubleshooting13A-49
INSPECTION PROCEDURE 38
MUT-II: Check if idling speed is unstable.
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
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
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
08 Purge control solenoid valve (Refer to P.13A-62.)NGCheck the purge control solenoid valve system
(Refer to P.13A-45, INSPECTION PROCEDURE 32.)
MUT-II Data list
11 Oxygen sensor
OK:600 ±1,000 mV during sudden racingNGCheck the oxygen sensor system. (Refer to P.13A-11, INSPECTION
PROCEDURE FOR DIAGNOSIS CODE 11.)
OK
MUT-II Data list
11 Oxygen sensor
OK:Changes between 0 ±400 mV and 600 ±1,000 mV during
idlingNGCheck the fuel pressure.
(Refer to P.13A-81.)OK1. Inspect the intake of
air into the air intake
system.

Broken intake
manifold gasket

Broken vacuum
hose

PCV valve does
not operate.

Broken air intake
hose
2. Check the injector for
clog.
OK
MUT-II Data list
27 Power steering fluid pressure switch (Refer to P.13A-57.)NGCheck the power steering
fluid pressure switch sys-
tem. (Refer to P.13A-43,
INSPECTION PROCE-
DURE 28.)
OK
MUT-II Data list
28 A/C switch (Refer to P.13A-57.)NGCheck the A/C switch and A/C relay system.
(Refer to P.13A-43. INSPECTION PROCEDURE 29.)
OK
MUT-II Data list
29 Inhibitor switch (Refer to P.13A-57.)NGCheck the ignition switch-ST and inhibitor switch system.
(Refer to P.13A-42, INSPECTION PROCEDURE 27.)
OK
MUT-II Data list
45 ISC Servo position (Refer to P.13A-57.)NGAdjust the basic idle speed. (Refer to P.13A-79.)
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-50
INSPECTION PROCEDURE 39
MUT-II: Engine stalling inspection when the engine is warmed up and idling.
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
MUT-II Data list
13 Intake air temperature sensor (Refer to P.13A-57.)NGCheck the intake air sensor system. (Refer to P.13A-12, INSPEC-
TION 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
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
11 Oxygen sensor
OK:Changes between 0 ± 400 mV and 600 ± 1,000 mV during
idlingNGCheck the fuel pressure.
(Refer to P.13A-81.)OK1. Inspect the intake of
air into the air intake
system

Broken intake
manifold gasket

Broken vacuum
hose

PCV valve does
not operate.

Broken air intake
hose
2. Check the injector for
clog.
OK
MUT-II Data list
27 Power steering fluid pressure switch (Refer to P.13A-57.)NGCheck the power steering
fluid pressure switch sys-
tem. (Refer to P.13A-43,
INSPECTION PROCE-
DURE 28.)
OK
MUT-II Data list
28 A/C switch (Refer to P.13A-57.)NGCheck the A/C switch and A/C relay system.
(Refer to P.13A-43, INSPECTION PROCEDURE 29.)
OK
MUT-II Data list
29 Inhibitor switch (Refer to P.13A-57.)NGCheck the ignition switch-ST and inhibitor switch system.
(Refer to P.13A-42, INSPECTION PROCEDURE 27.)
OK
MUT-II Data list
45 ISC servo position (Refer to P.13A-57.)NGAdjust the basic idle speed. (Refer to P.13A-79.)
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.)
OK
MUT-II Data list
11 Oxygen sensor
OK:Changes between 600 ± 1,000 mV during sudden racingNGCheck the oxygen sensor system. (Refer to P.13A-11, INSPECTION
PROCEDURE FOR DIAGNOSIS CODE 11.)

MPI ± Troubleshooting13A-51
INSPECTION PROCEDURE 40
MUT-II: Check if hesitation, sug, stumble or poor acceleration occurs.
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
MUT-II Data list
13 Intake air temperature sensor (Refer to P.13A-57.)NGCheck the intake air sensor system. (Refer to P.13A-12, INSPEC-
TION 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
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 DIAGNOS-
TIC CODE 21.)
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 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.)
OK
MUT-II Data list
11 Oxygen sensor
OK:Changes between 600 ± 1,000 mV during sudden racingNGCheck the oxygen sensor system. (Refer to P.13A-11, INSPECTION
PROCEDURE FOR DIAGNOSIS CODE 11.)
OK
MUT-II Data list
11 Oxygen sensor
OK:Changes between 0 ± 400 mV and 600 ± 1,000 mV during
idlingNGCheck the fuel pressure.
(Refer to P.13A-81.)OK1. Inspect the intake of
air into the air intake
system

Broken intake
manifold gasket

Broken vacuum
hose

PCV valve does
not operate.

Broken air intake
hose
2. Check the injector for
clog.