The idle speed of Chang 'an Star is unstable after overhaul.

According to this car, there are many types of engines, which can be summarized as follows:

A. Components that directly affect idle speed: throttle section: such as stepping motor, dirt (to be cleaned during maintenance), stuck valve, etc.

B. Matching after assembly: In case of power failure, relevant components need to be matched again or restored to the initial values.

C. sensors:

1, crankshaft position sensor, whether it is replaced or installed correctly, and whether there is any quality fault in the components.

2. Camshaft sensor.

3. Whether the cooling water temperature or air intake and oil pressure sensors are abnormal.

4, other electronic control (ignition, fuel) sensor parameter inspection.

5. Valve timing.

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D. fuel oil

1, whether the oil pressure is normal.

2. Whether the electronic oil pump is faulty.

3. The filter is blocked or replaced, or the oil supply is not smooth due to the parts themselves.

4. Nozzle: clogged, dirty or faulty, clean or replace it according to the actual situation.

5.ECU system failure.

E, electrical appliances

1, ignition coil; Check whether there is a fault. If ignition is abnormal, please replace it.

2. dividing line; Should be replaced after overhaul, if the resistance is abnormal or leaking, etc.

3. Spark plugs; Whether the replacement model (standard) after overhaul symbolizes the original model, such as calorific value.

4. Whether other circuit parts are abnormal or have assembly reasons.

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F, machinery

1. Re-inspect the assembly after overhaul to see if any parts are improperly installed or there are small errors in the adjustment of related "marks" (such as timing).

2. Internal assembly reasons.

3. Due to the reasons of individual parts of peripheral components (such as quality failure or "aging" need to be replaced), the engine is unstable, jittery, flameout or difficult to start.

4. Internal fit clearance of cylinder block and quality of fittings. It can also lead to.

5. Whether the construction work in the processing process is carried out according to the calibration and specifications.

Due to the different engines of this model (up to now), such as 465, 474, etc., it is suggested to phase out the solution according to the above method, and then judge according to the actual vehicle. In the process of maintenance, especially recall whether there are any defects in the assembly process, carefully identify each key point, and quickly find out the problem according to your own relevant experience.