Page 2652 - Foton Workshop Manual - Sauvana

62-600 DIAGNOSIS-ENGINE CONTROL SYSTEM

UNSTABLE IDLING (FLUCTUATED)

Fault phenomenon Diagnosis logic Possible reasons

• Inlet system • Leakage in the gas intake
• Fuel injector system
• Ignition timing • Leakage of the injector
• wrong mixture ratios • Ignition system
• Carbon decomposition of cylinder valve • Air fuel ratio
Unst able idling and inlet channel • Defective idle stepping motor
(fluctuated)
• Ignition system • Too low of the compression
• Air fuel ratio pressure
• Poor idling motor • Reverse connection of the
• Reverse connection of the before and before and rear of the oxygen
rear of the oxygen sensor sensor

Notice：
Whenthe motor idling runs, if the mixture gas distribution disorders, air intake system leaks
or some cylinder doesnot work due to the ignition system failure, it will cause the default of
no idle, too high of the idle speed, unstable idle or poor fast idle and other defaults.

Diagnosis Procedure
1. Check the motor data

(a). Ignition switch: LOCK。
(b). Connect the diagnosis tool with the fault diagnosis connector (16pins) on the lower
left of the dashboard.
(c). Ignition switch: Turn on the ignition switch, and start the diagnostic tool.
(d). Read the motor data shown on the diagnostic tool.

Check whether the data flow is normalor not.
YES>To step 2
No >Maintenance related faults.

2. Perform visual and external check

(a). Observe the rotation status and shaking degree of the motor.
(b). Observe the rotation status and shaking degree of the motor.
(c). Observe whether it is normal idle jitter or load idle jitter. (Turn on the air conditioner,
light, hanging gear and turn the steering wheel etc.)
(d). Whether the external parts of the motor are normal or not. Whether the vacuum
tube losses or damages or not; whether the wire connector looses or not.
(e). Whether it has the four phenomena of leakage of fuel, water, gas and electricity.
(f). Whether the exhaust pipe has the phenomena of “chug, chug” (indicating poor
combustion), black smoke, raw gasoline smell and other abnormal phenomenon.

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