What Causes the Engine Resonance and Buzzing Noise During Acceleration?
2 Answers
Causes of car body shaking during acceleration include a dirty throttle body and excessive carbon buildup in the fuel injectors and intake manifold. The reasons for body shaking vary under different conditions. Specific scenarios and solutions are as follows: Specific Scenarios: If the car engine shakes when starting, it is not normal, and sometimes there may even be a failure to start. The primary causes are a dirty throttle body and excessive carbon buildup in the fuel injectors and intake manifold. In cold conditions, carbon deposits can absorb some of the fuel, and if the fuel does not fully enter the combustion chamber, it can lead to unstable idling and difficulty starting. When driving at high speeds, the steering wheel may noticeably shake or vibrate at a certain speed, but this is not apparent at low speeds. In this case, it is essential to first rule out abnormal shaking caused by engine issues, as engine faults typically manifest at low speeds as well. Solutions for Car Body Shaking During Acceleration: If the car shakes noticeably during acceleration, visually inspect whether the balancing weights on the wheel rims are missing or if the wheel hubs are visibly deformed. If these areas show no issues, professional diagnostic equipment is required, as subtle deformations in the tie rods, suspension, or wheel hubs are difficult to detect with the naked eye. First, check if the left and right half-shafts are bent. Next, disassemble and inspect the inner walls of the inner CV joints for wear and pitting. In most cases, the issue is caused by a damaged inner CV joint. Modern cars are typically front-engine and front-wheel-drive, with inner CV joints often being telescopic to accommodate changes in the relative position between the transmission drive terminal and the driven wheels during driving. Upon disassembly, it can be observed that the inner walls of the inner CV joints—where they frequently contact the outer race of the needle bearings (i.e., the torque transfer points)—have developed pitting. During rapid acceleration, the engine and transmission assembly undergo slight lateral tilting, altering the position of these torque transfer points. Due to the angle between the half-shaft axis and the inner CV joint axis, these points shift axially during rotation, generating forces that push the car body side to side, resulting in the described sensation. Replacing the damaged inner CV joint or half-shaft can resolve the issue.
I've encountered this issue before with my old Focus. When accelerating to around 2000 RPM, the dashboard would vibrate with a buzzing sound, just like a phone vibrating on a table. The mechanic later diagnosed it as worn engine mounts - the rubber components had cracked, causing loss of vibration damping. Actually, besides mount issues, loose exhaust system connections can also cause resonance, especially in older vehicles where exhaust pipe hangers tend to break. Another common culprit is worn CV joints - particularly noticeable during hard acceleration when increased play in the joints creates that buzzing noise. My suggestion: do a quick self-check. With the engine cold, try rocking it vigorously - if there's excessive movement, it's likely the mounts. If you hear metallic scraping sounds from underneath, inspect the exhaust system. Don't delay fixing this - severe resonance can even crack dashboard plastic components.
