Why does the car body shake at idle speed?
3 Answers
Here are the reasons for car body shaking during idle speed: 1. Severe engine carbon deposits: The most common cause of car shaking is excessive dirt on the throttle or carbon buildup in the fuel injectors. When there is too much carbon deposit inside the engine, the gasoline sprayed by the cold start injector will be largely absorbed by the carbon deposits, resulting in an overly lean mixture during cold starts and making it difficult to start. In this case, the car will only start easily after the carbon deposits have absorbed enough gasoline to reach saturation. 2. Ignition system issues: Check the condition of the spark plugs, high-voltage wires, and ignition coils. Poor performance of the ignition system or weak spark plug firing can also cause such faults. The solution is to check if the spark plugs have excessive carbon buildup and replace them if necessary. 3. Unstable oil pressure: If you have already cleaned the engine carbon deposits, cleaned the throttle, replaced the oil pads and spark plugs, but still notice car body shaking at idle speed, it is recommended to check whether the fuel supply pressure and intake pressure sensors are functioning properly. Abnormal fuel pump supply pressure or incorrect readings and poor performance of the intake pressure sensor can also cause car body shaking.
My car also had an idling vibration issue before, especially when waiting at red lights. The entire seat was shaking, which felt extremely uncomfortable. Thinking carefully, there are quite a few common causes. For example, old spark plugs in an aging car may not ignite properly due to prolonged use, or excessive carbon buildup in the engine can lead to abnormal combustion. It could also be due to worn-out or loose engine mounts, causing instability while driving, or fuel supply issues in the fuel system leading to misfires and vibrations. Last time I took it to the repair shop, they found a problem with the ignition coil—replacing it made a big difference. Additionally, an unsecured exhaust pipe can also cause shaking, so these small components shouldn’t be overlooked during routine maintenance. Using the wrong fuel or faulty sensors can similarly affect idle conditions. In short, vibrations aren’t a minor issue—it’s safer to get it checked professionally for trouble codes rather than attempting DIY fixes that might waste money.
The car shakes violently when idling, even the steering wheel vibrates to the point of numbness, which definitely indicates a problem. The main cause is engine instability, possibly due to ignition system issues like worn-out spark plugs with weak sparks or a burnt coil. A clogged fuel pump causing insufficient fuel supply can also make the engine shake like it's gasping for air, and a dirty air filter restricting airflow is another contributing factor. Broken engine mounts losing their cushioning effect is even more noticeable, with clunking sounds audible at idle. My old car once shook due to poor fuel quality, but switching to proper fuel helped a lot. In such cases, first check if any warning lights are on the dashboard and inspect the spark plugs for severe carbon buildup. If the issue persists, have a technician scan it with a diagnostic tool—don't risk driving on the highway as it's too dangerous.
