What Causes Car Vibration at High Speeds but Not at Low Speeds?

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Car vibration at high speeds but not at low speeds can be caused by the following reasons: 1. Dirty air filter: The air filter is designed to protect the engine and reduce wear, usually requiring replacement every 10,000 kilometers. If not replaced in time, insufficient air intake can cause low idle speed, leading to engine vibration. Simply replacing the filter can solve the problem. 2. Broken high-voltage line: A broken high-voltage line refers to a break in the conductor core, which can affect ignition and cause engine vibration. Use a multimeter to measure the resistance and replace the one with significantly higher resistance. 3. Spark plug lifespan: Spark plugs have a limited lifespan. After 30,000-40,000 kilometers, their ignition efficiency noticeably decreases, affecting ignition. This is the most common issue, and replacing all spark plugs can resolve it.