What causes uneven idle speed in BMW B48 combustion control?
2 Answers
Reasons for uneven idle speed in BMW B48 combustion control: Carbon deposits in the engine; Aging engine mounts; Unstable oil pressure. Severe engine carbon buildup: A very common cause of car shaking is a dirty throttle valve or excessive carbon deposits in the fuel injectors. When there is too much carbon buildup inside the engine, the gasoline sprayed by the cold start injector will be largely absorbed by the carbon deposits; Immediate carbon cleaning is required. Aging engine mounts: Engine mounts are essentially the shock absorption system of the engine. They are responsible for absorbing minor vibrations during engine operation. If the engine mounts are faulty, these vibrations will be transmitted to the steering wheel and cabin, causing shaking during idle. Unstable oil pressure: If the fuel pump supply pressure is abnormal or the intake pressure sensor values are incorrect or malfunctioning, it can cause body shaking. The solution is to check the oil pressure and replace components if necessary.
My BMW B48 started experiencing idle vibration while driving, feeling like the engine is jumping on the seat. It's mainly caused by incomplete combustion, common culprits like worn-out spark plugs causing uneven ignition, or clogged fuel injectors due to carbon buildup. A dirty throttle body is also troublesome, affecting the air-fuel ratio and causing erratic idle speed. I tried replacing the spark plugs and air filter myself, which slightly alleviated the symptoms. But for a complete fix, it's necessary to check if the oxygen sensor has signal drift or if the electronic control unit settings are off. Unstable idle not only makes driving uncomfortable but also leads to increased fuel consumption and engine damage over time. It's recommended to visit a professional shop for a diagnostic scan to identify the fault codes early.
