Information Summary and Preparation
-1
(9) Start-up normal but idle speed unstable or
stall with load such as front lamp applied
General trouble location: 1. ISC 2. Nozzle.
Procedure for general diagnoses:
No. Operating
Procedure Detection
Results
Subsequent Steps
1
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
2
Check if the engine’s output power is increased with the load
applied; use the EMS diagnosis tester to check any change in
the ignition advance angle, duration of fuel injection, and air
input.
Yes
Go to Step 4.
No Next
step
No
Repair the air
regulating system.
3
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
4
Check the ECU circuit
(10) Start-up normal but idle speed too high
General trouble location: 1. Air throttle and idle air bypass; 2. Vacuum tube; 3, ISC ; 4. Engine
temperature sensor; 5. Ignition timing.
Procedure for general diagnoses:
No. Operating
Procedure Detection
Results
Subsequent Steps
1
Check the throttle cable for jammed or too tight.
Yes Adjustment
No Next
step
2
Check the air intake system and the connected vacuum tube
for any leakage.
Yes
Repair the air intake
system.
No Next
step
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; check if the engine’s the idle speed is too high.
Yes
Correct circuits or
replace any sensor.
No Next
step
5
Check if mechanical ignition timing of the engine is
conformable to specifications.
Yes Next
step
No
Correct ignition
timing.
6
Check the ECU circuit
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