What is the reason for unstable engine speed? What about the solution?
Usually, this is caused by the leakage of the intake system and valves, excessive scaling of the throttle valve and intake pipe, and improper idle intake. Unstable engine idle speed usually means that the idle speed jitter exceeds the expected value of 20r/min or the speed jitter is serious. Suggest going to the 4S store to check the specific reasons.
The unstable idle speed of automobile is mainly manifested by the fluctuation of tachometer pointer and unstable idle speed. Unstable idle speed is often accompanied by idle jitter. Unstable idle speed is one of the most common engine faults, ranging from large to small. Under normal conditions, if the idle speed is too high, the fuel consumption will be relatively high, but if the idle speed is too low, the engine will shake or even stall.
1.Throttle oil storage and carbon deposit:
A restriction in the intake air will cause idling. Carbon or oil in the throttle is the most common cause of unstable idle speed. The carbon deposit on the throttle will affect the opening and intake volume, and make the engine speed fluctuate from high to low after the cold start of the car, which is very unstable and accompanied by strong jitter. The throttle valve has serious oil or carbon deposits, including dirty air intake, which makes it difficult to start the car in cold weather. The throttle is dirty and needs cleaning.
2. Spark plug fault:
The spark plug will also deposit carbon, and the activity of the spark plug can be restored by cleaning. However, some spark plugs will lose performance when they are close to their service life. The weak spark of the spark plug on a single cylinder will affect the performance of the vehicle. We know that the spark plug failure will lead to the "misfire" symptom of the car, but the slight failure of the spark plug on a single cylinder will lead to the unstable idle speed symptom. Cleaning or replacing spark plugs is also an option to solve this problem.
3.Oil blockage, intake pipe failure:
When the fuel circuit represented by the injector is blocked, the fuel supply pressure will be insufficient, the fuel atomization will be poor, the mixture ratio will be unbalanced and the combustion will be incomplete, which will lead to related failures. If the intake pipe leaks, it will affect the real data reflected by the air flow meter, resulting in inaccurate ECU control of the intake air, unbalanced mixing ratio, and unstable engine idle speed. Cleaning the oil circuit is also a maintenance project.
4.Related sensor failure:
The relevant sensor failure will make the ECU unable to control the correct air-fuel ratio, such as water temperature sensor, oxygen sensor, throttle position sensor and other common faults. The water temperature sensor is generally installed on the water jacket of the cylinder block or cylinder head of the engine. It directly contacts the antifreeze to measure the temperature, and sends the relevant reference data to the ECU. Once the water temperature sensor fails, the vehicle will have problems such as increased fuel consumption, unstable idle speed and abnormal speed. On the other hand, the failure of the throttle position sensor and the front oxygen sensor will lead to the air-fuel ratio error, resulting in incomplete combustion of the mixture and related failures. The relevant sensor needs to be replaced.
