What Causes Intermittent Idle Vibration in BMW 5 Series?
2 Answers
BMW 5 Series intermittent idle vibration may be caused by the following reasons: 1. Severe engine carbon deposits: When there is excessive carbon buildup inside the engine, the gasoline injected by the cold start fuel injector will be largely absorbed by the carbon deposits. This results in an overly lean air-fuel mixture during cold starts, making the engine difficult to start. Under these conditions, the engine only starts easily after the carbon deposits become saturated with gasoline. After starting, the gasoline adsorbed on the carbon deposits will be drawn into the combustion chamber by the engine's vacuum suction, making the mixture too rich. This alternating lean-rich condition of the combustible mixture causes idle vibration after cold starts. The lower the temperature, the more fuel is required for cold starts, and the presence of carbon deposits significantly affects whether cold starts proceed smoothly. 2. Ignition system issues: Poor spark plug performance can also cause such vibration phenomena. 3. Unstable fuel pressure: If the fuel pump supply pressure is abnormal or if there are incorrect readings or malfunctions in the intake pressure sensor, it can lead to vehicle vibration.
I've been driving a BMW 5 Series for years, and the occasional shake at idle is really annoying. It might be due to old spark plugs causing unstable ignition, especially after tens of thousands of kilometers. Carbon buildup clogging the fuel injectors is also common, particularly after using low-quality gasoline. Aging engine mounts can make the whole body shake, and old BMWs are especially prone to this issue. BMW's electronic systems are too complex, and when sensors fail, the shaking gets worse. Regular maintenance is crucial—cleaning the intake and throttle body can help a lot. Don’t take it lightly; shaking might seem minor, but it can accelerate engine wear. Get it checked at a repair shop ASAP.
