Information Summary and Preparation
-1
(6) Start-up normal but idle speed unstable anytime
General trouble location: 1. Water in fuel; 2. Nozzle; 3. Spark plug; 4. Air throttle and idle air
bypass; 5.Air intake; 6. ISC; 7. Ignition timing; 8. Spark plug; 9. 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 Idle governor for the control valve jammed.
Yes Change
No Next
step
3
Check the spark plug and its model and gap conformable to
specifications.
Yes Next
step
No Adjustment
or
change
4
Check the air throttle and the idle air bypass for any carbon
deposition.
Yes Cleaning
No Next
step
5
Disassemble the nozzle and check any leakage or jam in the
nozzle with a nozzle cleaner & analyzer.
Yes
Replace 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 if mechanical ignition timing of the engine is conformable
to specifications.
Yes Next
step
No
Correct ignition timing.
9
Check the ECU circuit
15
