Mitsubishi FUEL Manual page 267

INSPECTION PROCEDURE 7
Unstable idling (rough idle, hunting)
This malfunction is probably caused by a faulty ignition system, improper air/fuel ratio,
a faulty electronic-controlled throttle valve system, improper compression pressure,
etc. As many causes can be suspected, diagnose from easier items.
Has the battery been disconnected recently?
MUT-II Self-Diag code
Is a diagnosis code displayed?
Does the engine idle speed fluctuates excessively (excessive hunt-
ing)?
MUT-II Data list
79 Throttle position sensor (1st channel) (Refer to P.13I-98.)
MUT-II Data list
26 Accelerator pedal position switch (Refer to P.13I-98.)
MUT-II Data list
13 Intake air temperature sensor (Refer to P.13I-98.)
MUT-II Data list
25 Barometric pressure sensor (Refer to P.13I-98.)
MUT-II Data list
21 Engine coolant temperature sensor (Refer to P.13I-98.)
MUT-II Actuator test
08 Purge control solenoid valve (Refer to P.13I-104.)
MUT-II Data list
59 Oxygen sensor (rear)
D Transmission: 2nd gear <M/T>, L range <A/T>
D Driving with throttle widely open
OK: 600 - 1,000 mV
MUT-II Data list
11 Oxygen sensor (front)
OK: 600 - 1,000 mV when the engine is suddenly raced
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GDI -
No
No
No
OK
OK
OK
OK
OK
OK
OK
OK
Troubleshooting
Probable cause
D Malfunction of the ignition system
D Malfunction of the air/fuel ratio control system
D Malfunction of the electronic-control throttle valve
system
D Improper compression pressure
D Air sucking into the air intake system
Yes
Warm up the engine, and then let it run at idle for approx. ten
minutes.
Yes
Refer to P.13I-11, INSPECTION CHART FOR DIAGNOSIS
CODES.
Yes
Clean around the throttle valve. (Refer to P.13I-98*.)
NG
Check the throttle valve position feedback system.
(Refer to P.13I-57, INSPECTION PROCEDURE FOR DIAGNOSIS
CODE P1221.)
NG
Check the accelerator pedal position switch system. (Refer to
P.13I-93, INSPECTION PROCEDURE 29.)
NG
Check the intake air temperature sensor system.
(Refer to P.13I-17, INSPECTION PROCEDURE FOR DIAGNOSIS
CODE P0110.)
NG
Check the barometric pressure sensor system. (Refer to P.13I-15,
INSPECTION PROCEDURE FOR DIAGNOSIS CODE P0105.)
NG
Check the engine coolant temperature sensor. (Refer to P.13I-18,
INSPECTION PROCEDURE FOR DIAGNOSIS CODE P0115.)
NG
Check the purge control solenoid valve system. (Refer to P.13I-54,
INSPECTION PROCEDURE FOR DIAGNOSIS CODE P0443.)
NG
Check the oxygen sensor (rear) system. (Refer to P.13I-28, IN-
SPECTION PROCEDURE FOR DIAGNOSIS CODE P0136.)
NG
Check the oxygen sensor (front) system. (Refer to P.13I-25, IN-
SPECTION PROCEDURE FOR DIAGNOSIS CODE P0130.)
13I-73