Information Summary and Preparation
-1
(8) Start-up normal but idle speed unstable with warm-up finished
General trouble location: 1. Water in fuel; 2. Engine temperature sensor; 3. Spark plug; 4. Air
throttle and idle air bypass; 5. Air intake; 6. ISC; 7. Engine mechanism.
Procedure for general diagnoses:
No. Operating
Procedure Detection
Results
Subsequent Steps
1
Check any jam of the air filter and leakage of the air intake.
Yes
Repair the air intake
system.
No Next
step
2
Check the spark plug and its model and gap conformable to
specifications.
Yes Next
step
No
Adjustment or
change
3
Remove the ISC and check the air throttle, the ISCand the idle air
bypass for any carbon deposition.
Yes Clean
relevant
parts.
No Next
step
4
Press the engine temperature sensor connector and start the engine
to check any instability of the idle speed during warm-up of the
engine.
Yes
Correct circuits or
replace any sensor.
No Next
step
5
Disassemble the nozzle and check the nozzle leaking or blocked, or
the flow out of tolerance with a nozzle cleaner & analyzer.
Yes
Change the defective
nozzle.
No Next
step
6
Check fuel and observe any trouble attributed to fuel just added.
Yes Change
fuel.
No Next
step
7
Check pressure of the engine cylinder and find any big difference
in pressure.
Yes
Eliminate any
mechanical trouble
of the engine.
No Next
step
8
Check the ECU circuit
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