What Causes Car Shaking at Low Speed but Normal at High Speed?

[VonBeckett]

Car shaking at low speed but normal at high speed can be caused by the following reasons: Excessive engine carbon deposits: A dirty throttle body or excessive carbon deposits on the fuel injectors are the most likely causes of car shaking. When starting the car, the fuel on the carbon deposits will be sucked into the cylinder for combustion. Due to the fluctuating amount of combustible mixture in the engine, the car body will shake during cold starts. Ignition system malfunction: This is also an important reason for car body shaking at idle. If there are issues with the spark plugs, high-voltage wires, or ignition coils, the car body will shake when starting. At this time, you can check if there is too much carbon deposit on the spark plugs, and replace them with new ones if necessary.

[DiMaci]

My old ride shakes like crazy at low speeds but runs smooth on the highway. Took it to the shop and found out the engine mount bushings were completely cracked - when these age, they lose all damping effect, letting low-frequency vibrations transmit directly into the chassis. The spark plugs were another issue - still original after 50,000+ km with widened gaps causing misfires. Carbon buildup was clogging both the throttle body and fuel injectors, leading to uneven idle fuel delivery. To top it off, two wheel balancing weights had fallen off - while unnoticeable at highway speeds, they caused obvious steering wheel vibrations in city driving. Pro tip: replace aging rubber components promptly and clean carbon deposits regularly - way cheaper than waiting for major repairs.

[GageMarie]

Last time in the car enthusiast group, we discussed the issue of low-speed shaking, which several of us who frequently drive long distances have encountered. The most likely cause is an issue with the ignition system, such as worn-out spark plugs or poor contact in the ignition coils, which can lead to irregular operation of individual cylinders, especially noticeable at low RPMs. Another possible culprit is the engine mounts—those are essentially large rubber cushions that can crack and fail under prolonged high-temperature conditions, directly transmitting engine vibrations to the cabin. The fuel system is also worth checking, as unstable fuel pump pressure or clogged fuel injectors can cause fluctuations during low-speed fuel delivery. My personal approach to handling this is to consistently use qualified fuel additives, regularly clean the throttle body, and replace spark plugs every 40,000 kilometers.

[LeArya]

When I first bought the car, I was also troubled by low-speed shaking. I specifically consulted an experienced mechanic, and the principle is quite simple: at high speeds, the engine RPM is high, so minor issues aren't noticeable; but at low speeds, it's a different story. Focus on checking three key areas: first, the ignition coil connectors—if they're loose, it can cause poor ignition; second, the carbon buildup on the back of the throttle body—if it exceeds 2mm thick, it disrupts the air intake; third, inspect the engine mounts underneath—use a flashlight to check for cracks. There's also an easily overlooked component: the mass airflow sensor—if it's dirty, it affects the air-fuel mixture ratio. Now, I've developed a habit of doing a thorough cleaning at year-end, and my 5-year-old car hasn't experienced any shaking since.