What causes the B12 engine idle speed to be unstable, fluctuating between high and low?
1 Answers
The unstable idle speed of the B12 engine, fluctuating between high and low, can be attributed to the following reasons: 1. Dirty intake tract: A clogged intake tract can cause idle fluctuations, and the presence of carbon deposits or oil in the throttle body is the most common cause of unstable idle speed. Carbon deposits in the throttle body can affect its opening, thereby impacting the air intake volume, leading to erratic engine speed fluctuations after a cold start, accompanied by strong vibrations. Severe oil or carbon deposits in the throttle body, including a dirty intake tract, can make it difficult to start the car in cold weather. Cleaning the throttle body is necessary and is considered a routine maintenance task. 2. Weak spark from spark plugs: Spark plugs can also accumulate carbon deposits, which can be cleaned to restore their activity. However, some spark plugs may be nearing the end of their lifespan, leading to reduced performance. Weak sparks from spark plugs in individual cylinders can affect the car's performance. Faulty spark plugs can cause the car to exhibit 'misfire' symptoms, but minor faults in spark plugs of individual cylinders can result in unstable idle speed. Therefore, when the car experiences unstable idle speed, cleaning or replacing the spark plugs is also a viable solution to the problem.
