Mitsubishi MOTORS Space Runner 1999 Workshop Manual Supplement page 407

13A-48
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
14 Throttle position sensor (2nd channel) (Refer to P.13A-75.)
MUT-II Data list
79 Throttle position sensor (1st channel) (Refer to P.13A-79.)
MUT-II Data list
26 Accelerator pedal position switch (Refer to P.13A-76.)
MUT-II Data list
13 Intake air temperature sensor (Refer to P.13A-75.)
MUT-II Data list
25 Barometric pressure sensor (Refer to P.13A-76.)
MUT-II Data list
21 Engine coolant temperature sensor (Refer to P.13A-76.)
MUT-II Actuator test
08 Purge control solenoid valve (Refer to P.13A-80.)
MUT-II Data list
11 Oxygen sensor
OK: 600 – 1,000 mV when the engine is suddenly raced
MUT-II Data list
11 Oxygen sensor
OK: 0 – 400 mV and 600 – 1,000 mV alternates when the
engine is idling (wait for four minutes after the engine
started).
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GDI –
No
No
No
OK
OK
OK
OK
OK
OK
OK
OK
OK
Troubleshooting
Probable cause
Malfunction of the ignition system
Malfunction of the air/fuel ratio control system
Malfunction of the electronic-control throttle valve
system
Improper compression pressure
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.13A-13, INSPECTION CHART FOR DIAGNOSIS
CODES.
Yes
Clean around the throttle valve. (Refer to P.13A-96.)
NG
Check the throttle position sensor (2nd channel) system. (Refer
to P.13A-17, INSPECTION PROCEDURE FOR DIAGNOSIS
CODE 14.)
NG
Check the throttle valve position feedback system. (Refer to
P.13A-36, INSPECTION PROCEDURE FOR DIAGNOSIS CODE
92.)
NG
Check the accelerator pedal position switch system. (Refer to
P.13A-67, INSPECTION PROCEDURE 28.)
NG
Check the intake air temperature sensor system. (Refer to P.13A-16,
INSPECTION PROCEDURE FOR DIAGNOSIS CODE 13.)
NG
Check the barometric pressure sensor system. (Refer to P.13A-22,
INSPECTION PROCEDURE FOR DIAGNOSIS CODE 25.)
NG
Check the engine coolant temperature sensor. (Refer to P.13A-18,
INSPECTION PROCEDURE FOR DIAGNOSIS CODE 21.)
NG
Check the purge control solenoid valve system. (Refer to P.13A-70,
INSPECTION PROCEDURE 31.)
NG
Check the oxygen sensor system. (Refer to P.13A-14, INSPECTION
PROCEDURE FOR DIAGNOSIS CODE 11.)
NG
Measure fuel high-pressure between the fuel pump (high pressure)
and injector. (Refer to P.13A-98.)
OK
Check that air is sucked in the air intake system.
Broken intake manifold gasket
Damaged vacuum hose
Damaged air intake hose
NG
Repair