What are the reasons for BMW car body shaking during startup?
3 Answers
There are three main reasons for BMW car body shaking during startup. Below is a detailed introduction to these three reasons: 1. Severe carbon deposits: This may be due to a dirty throttle valve or excessive carbon deposits in the fuel injector and intake manifold. In cold conditions, carbon deposits can absorb some fuel, leading to incomplete combustion, which results in unstable idling and difficulty starting. The throttle valve or fuel system should be cleaned promptly. 2. Ignition system failure: When the ignition system is not working properly or the spark plug firing condition is poor, it can easily lead to such faults. Check if the spark plugs have excessive carbon deposits and replace them if necessary. 3. Unstable oil pressure: If you have already cleaned the engine carbon deposits, cleaned the throttle valve, replaced the oil pad and spark plugs, but still notice body shaking during idling, you should check whether the fuel supply pressure and intake pressure sensor are normal. When the fuel pump supply pressure is abnormal or the intake pressure sensor value is incorrect, it can easily cause body shaking.
Having driven a BMW for several years, I often encounter body shaking during startup. The most common causes are aging spark plugs or ignition coil issues, leading to uneven ignition; followed by fuel system problems like clogged injectors or insufficient fuel pump pressure affecting fuel supply; severe carbon buildup on pistons or valves causing incomplete combustion; or aging engine mounts or suspension damper rubber exacerbating overall vibration. Cold starts, when fluids aren't warmed up and lubrication is poor, make shaking more noticeable. I recommend starting with simple solutions: check and replace spark plugs and clean the air filter. Avoid using low-quality fuel to reduce carbon buildup. Regular maintenance is key—I perform an engine scan every six months to prevent issues. If DIY fixes don't work, promptly visit a professional shop to read fault codes and check sensors, such as the crankshaft position signal, for errors. Safe driving shouldn't be taken lightly—never ignore abnormal vibrations.
In repair shops, BMW starting vibration issues are frequently addressed. Main causes include ignition component problems such as worn spark plugs or failed coils; fuel supply issues like clogged filters or unstable pump voltage; carbon buildup inside the engine affecting air-fuel mixture; loose engine mounts transmitting excessive vibrations; and sometimes dirty throttle bodies causing stiff operation. Diagnosis starts with OBD tool scans to check for sensor faults, followed by manual inspection of loose wiring connections. Treatment measures: regularly replace spark plugs and engine oil to maintain cleanliness, avoid frequent short trips to reduce carbon buildup. For safety, if vibration is accompanied by abnormal noises, stop immediately for inspection to prevent sudden failures and ensure smooth, reliable driving.
