What causes slight shaking when the car is first started?
4 Answers
Possible causes of car shaking are as follows: 1. Uneven brake disc surface with excessive radial runout. This causes inconsistent contact between brake pads and discs during braking, resulting in fluctuating braking force and vehicle vibration, particularly noticeable during light braking. 2. Significant deviation in wheel alignment data. The vehicle becomes difficult to control during acceleration with slight shaking. 3. Improper tire pressure (either too high or too low). Higher speeds with overinflated tires intensify vibration, while underinflation causes vehicle drift. 4. Abnormal tire wear. Inconsistent tire surface wear due to improper wheel alignment or rim deformation leads to vibration during driving.
Cold start shaking is a very common issue. Just last week, I encountered a similar situation when helping a neighbor check their car—the steering wheel was vibrating upon startup. It's most likely a problem with the fuel system, possibly clogged injectors causing unstable operation in some cylinders. Carbon buildup is also a hidden culprit, especially when it accumulates on the back of the intake valves, acting like a mask on the engine. Using low-quality gasoline makes things worse—I’ve personally seen cases where the fuel pump filter was completely clogged with debris. Also, check the engine mounts; when they age, their damping effect is lost, and engine vibrations transfer directly into the cabin. I recommend focusing on these areas during the next maintenance and having the mechanic scan for trouble codes.
It depends on your car's mileage. For new cars shaking within 30,000 km, first check the ignition system. Spark plugs replaced off-season are prone to enlarged gaps – my friend's Golf shook like this for half a year. For vehicles over 50,000 km, suspect carbon deposits in cylinders, especially the black sludge on the back of direct injection engine valves, thick enough to use as an inkstone. Older cars should also watch for engine mount rubber parts – these inevitably age around ten years. My old Passat shook like a massage chair last year because of this. The trickiest is incorrect air-fuel mixture ratio, caused by faulty oxygen sensors or stuck throttle valves, requiring a diagnostic tool to confirm. Remember to regularly use fuel system cleaner for carbon removal.
A few shakes upon startup are normal, but continuous shaking should be taken seriously. The most common cause is worn-out spark plugs. Last year, my car had this issue, and the tachometer was dancing like at a disco when stopped at a red light. Dirty throttle bodies are also worth attention, especially for cars frequently driven short distances, as sludge can cause inconsistent air intake. Another easily overlooked issue is the mass air flow sensor—oil film on it can lead to false readings. For cars with auto start-stop, also check the starter motor gears for wear. The solution is straightforward: first replace the spark plugs and air filter, then clean the throttle body if needed, and finally check the electrical circuits. After servicing, my car no longer had this issue.
