Maintenance Manual for J2 Sedan
Electronic Control System
of Engine
233
Trouble phenomenon 7: Normal start-up but unstable idling during the warming-up
General trouble position:
1.
Poor quality of fuel; 2. Coolant temperature sensor; 3.Spark plug; 4.Throttle body and idle bypass
air passage; 5.Intake passage; 6.Idle adjustor; 7.Mechanical part of engine.
General diagnosis procedure:
No.
Operating Steps
Detection
Results
Subsequent Steps
Yes
Repair air intake
system
1
Check air filter for blockage and air intake passage for leakage.
No
Next step
Yes
Next step
2
Check the spark plug of each cylinder to observe whether its model
and gap are in compliance with the specification.
No
Adjust or replace
Yes
Wash related
components
3
Dismantle the idle adjustor to check whether there is carbon deposit
in the air throttle body, idle adjustor or idle bypass air passage.
No
Next step
Yes
Repair circuit or
replace sensor
4
Pull out the connector of coolant temperature sensor and start the
engine to observe whether the idle speed of engine is unstable
during warming-up.
No
Next step
Yes
Failure of
Replacement
5
Dismantle the fuel injector and check whether there is leakage,
blockage or too poor flow in the fuel injector with cleaning analyzer
special for fuel injector.
No
Next step
Yes
Change fuel
6
Check fuel condition and observe whether the trouble phenomenon
occurs just after adding the fuel.
No
Next step
Yes
Eliminate the
mechanical trouble of
engine
7
Check pressure of all the cylinders and observe whether the
pressure difference of each engine cylinders is large.
No
Next step
Yes
Diagnosis help
8
Turn on the ignition switch and check whether the power supply
and earthing are normal.
No
Repair related circuit
