Why does the resonance disappear when accelerating at idle?
4 Answers
The reasons why engine vibration at idle disappears when accelerating are: 1. Changes in fuel injection quantity cause the engine speed to fluctuate; 2. Faulty fuel pump pressure regulator or sensor leads to incorrect fuel injection correction signals; 3. Cracked vacuum booster pipe; 4. Carbon buildup or dirt on the throttle body, or incorrect position of the throttle position sensor. Additional information: An engine (Engine) is a machine capable of converting other forms of energy into mechanical energy, including internal combustion engines (reciprocating piston engines), external combustion engines (Stirling engines, steam engines, etc.), jet engines, electric motors, etc. The term engine can refer to either the power generation device or the entire machine including the power unit.
Ah, my old buddy who's been driving for over twenty years often encounters this situation where the car hums at idle but the noise disappears when accelerating. It's mostly due to aging or loose engine mounts. At low idle speeds, the vibrations happen to match the defects in the mounts, causing resonance. When you step on the gas, the RPM increases and the frequency changes, so the resonance disappears. Additionally, if the exhaust system's hangers are damaged, it can also cause this. The exhaust pipe shakes severely at idle but stabilizes with high-speed airflow, reducing vibrations. It's recommended to visit a repair shop as soon as possible to avoid major issues like mount breakage or engine displacement. Usually, after parking, take some time to listen to the engine compartment sounds to detect signs of aging early.
As a regular car owner, I once noticed the steering wheel vibrating so much it made my hands numb while waiting at a traffic light, but it stopped once I started driving. After inspection, it turned out a connection point in the exhaust system was loose, causing the exhaust pipe vibrations to spread throughout the car body at idle. When accelerating, the increased RPM changed the vibration frequency, eliminating the resonance. It could also be an issue with the driveshaft balance, which is common in rear-wheel-drive vehicles. Alternatively, uneven ignition system performance might cause engine shaking, which stabilizes at higher speeds and stops the vibration. The solution is simple: have a professional mechanic diagnose the problem and replace any faulty parts—avoid DIY fixes to prevent damaging the car.
From a DIY enthusiast's perspective: Checking for idle resonance isn't difficult. First, open the engine hood to inspect if the engine mounts have cracks or are loose; shake the exhaust pipe to confirm if the hangers are intact. Sometimes just tightening loose screws will do. Check if the driveshaft is balanced, especially for rear-wheel drive vehicles. If the spark plugs are old, try replacing them. The vibration disappearing when accelerating is because the higher RPM shifts the vibration frequency away from the resonance point. When doing it yourself, pay attention to safety to avoid burns and make sure you have all the necessary tools ready.
