Mitsubishi FUEL Manual page 151

INSPECTION PROCEDURE 8
Unstable idling (Rough idling, hunting)
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.
Were the battery terminals disconnected?
MUT-II Self-Diag code
Are diagnosis codes displayed?
Does idling speed fluctuate excessively?
Check the ISC servo for operation sound. (Refer to P.13A-199*.)
Check the injector for operation sound.
MUT-II Data list
26 Idle position switch (Refer to P.13A-176.)
MUT-II Data list
13 Intake air temperature sensor (Refer to P.13A-176.)
MUT-II Data list
25 Barometric pressure sensor (Refer to P.13A-176.)
MUT-II Data list
21 Engine coolant temperature sensor (Refer to P.13A-176.)
MUT-II Actuator test
08 Purge control solenoid valve (Refer to P.13A-183.)
MUT-II Actuator test
10 EGR control solenoid valve (Refer to P.13A-183.)
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MPI <6A1> -
No
No
No
OK
OK
OK
OK
OK
OK
OK
Troubleshooting
Probable cause
D Malfunction of the ignition system
D Malfunction of air/fuel ratio control system
D Malfunction of the ISC system
D Malfunction of the purge control solenoid valve system
D Malfunction of the EGR solenoid valve system
D Poor compression
D Drawing air into exhaust system
Yes
After warming-up, let the engine run at idling for 10 minutes.
Yes
Refer to P.13A-99, INSPECTION CHART FOR DIAGNOSIS
CODES.
Yes
Clean the throttle body. (Refer to P.13A-184*.)
Check and adjust the fixed SAS. (Refer to P.13A-187*.)
Check trouble symptom.
Inspect the intake of air into the air intake system
D Broken intake manifold gasket
D Broken air intake hose
D Broken vacuum hose
D Positive crankcase ventilation valve does not operate.
NG
Check the ISC system. (Refer to P.13A-137,INSPECTIONPROCE-
DURE FOR DIAGNOSIS CODE P0505.)
NG
Check the injector system. (Refer to P.13A-127, INSPECTION
PROCEDURE FOR DIAGNOSIS CODE P0201, P0202, P0203,
P0204, P0205, P0206.)
NG
Check the idle position switch system. (Refer to P.13A-139, IN-
SPECTION PROCEDURE FOR DIAGNOSIS CODE P0510.)
NG
Check the intake air temperature sensor system. (Refer to
P.13A-105, INSPECTION PROCEDURE FOR DIAGNOSIS CODE
P0110.)
NG
Check the barometric pressuresensor system. (Refer to P.13A-103,
INSPECTION PROCEDURE FOR DIAGNOSIS CODE P0105.)
NG
Check the engine coolant temperature sensor system.
(Refer to P.13A-106, INSPECTION PROCEDURE FOR DIAGNO-
SIS CODE P0115.)
NG
Check the purge control solenoid valve system.
(Refer to P.13A-136, INSPECTION PROCEDURE FOR DIAGNO-
SIS CODE P0443.)
NG
Check the EGR control solenoid valve system. (Refer to P.13A-133,
INSPECTION PROCEDURE FOR DIAGNOSIS CODE P0403.)
13A-151
NG