Service manual

Information Summary and Preparation 1
18
(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. Idle governor; 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 idle governor and check the air throttle, the idle
governor, and 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
Connect an EMS adapter and press the power switch to check
voltages at Pins 5#, 10#, and 23#; check grounding at Pins 2# and
21#.
Yes Diagnosis assist
No
Repair the relevant
circuits.