What causes unstable idle speed when starting a Jetta in the morning?
1 Answers
Jetta car unstable idle speed when starting in the morning may be caused by the following reasons: Carbon buildup in the throttle body: Blockage in the intake tract can lead to idle fluctuations, and carbon deposits or oil accumulation in the throttle body are the most common causes of unstable idle speed. Carbon buildup affects the throttle opening, which in turn impacts the air intake volume, causing the engine speed to fluctuate erratically after a cold start, accompanied by noticeable vibrations. Severe oil accumulation or carbon deposits in the throttle body, including a dirty intake tract, can make the car difficult to start in cold weather. Cleaning the throttle body is necessary in such cases, and it is considered a routine maintenance task. Weak spark from spark plugs: Spark plugs can also accumulate carbon deposits, which can be cleaned to restore their performance. However, some spark plugs may be nearing the end of their lifespan, leading to reduced efficiency. Weak sparks from individual spark plugs can affect the car's performance. Faulty spark plugs may cause "misfiring," but minor issues with individual spark plugs can result in unstable idle speed. Therefore, cleaning or replacing spark plugs is also a viable solution when the car exhibits unstable idle speed.
