What Causes Vibration When Idling in D Gear?
2 Answers
The following are the reasons for vibration when idling in D gear: 1. High engine speed: When the engine speed is too high during cold start, the torque converter transmits more power, resulting in greater impact and more noticeable vibration when shifting gears. 2. Brake not fully engaged: When shifting gears, the engine's power is directly transmitted to the wheels. If the brake is not fully engaged, the wheels may move slightly, causing the vehicle to jerk forward with a strong vibration sensation. 3. Brake released too early: When the traffic light turns green, shifting into drive and releasing the brake to start can cause the vehicle to lurch forward violently if the brake is released too soon, leading to a sudden power combination. Since the automatic transmission gear lever does not directly control the gear position but acts as a signal device, different signals are sent to the transmission control system when different gears are engaged, and the transmission control system then completes the gear shift.
When I was driving an automatic transmission car, I encountered a situation where the car would shake when idling in D gear, which was quite annoying. There are several main reasons for this: the engine has significant issues, such as spark plugs that haven't been replaced for years and become unstable after aging, causing uneven engine speed; the fuel system, like clogged fuel injectors, leads to poor fuel supply; or a dirty air flow meter obstructs air intake, resulting in incomplete combustion. The transmission is also related—when in D gear, the torque converter might not lock correctly, causing imbalance in the drive and resulting in shaking. Last time my car shook severely, it turned out the engine mount was worn out, and the loose bracket transmitted the vibrations. These issues may seem minor, but neglecting them long-term could lead to spark plug erosion, accelerated transmission wear, or even affect driving safety. Later, I started regular maintenance, checking the spark plugs and engine mounts every two years, and now the problem has basically disappeared.
