What Causes the Car to Shake When Accelerating to Around 40 km/h?
3 Answers
Shaking when accelerating to around 40 km/h may be caused by carbon buildup in the intake system, specifically a large amount of gummy carbon deposits near the valve seat and idle speed motor, leading to overly rich or lean air-fuel mixtures, or a dirty throttle. The following are daily maintenance methods for the engine: 1. Regularly clean the crankcase: During engine operation, high-pressure unburned gases, acids, moisture, sulfur, and nitrogen oxides from the combustion chamber enter the crankcase through the gap between the piston rings and cylinder walls, mixing with metal particles from component wear to form sludge. Small amounts remain suspended in the oil, while larger amounts precipitate, clogging filters and oil passages, making engine lubrication difficult and causing wear. Additionally, oil oxidation at high temperatures can create varnish and carbon deposits that stick to the pistons, increasing fuel consumption, reducing power, and in severe cases, causing piston rings to seize and leading to cylinder scoring. Therefore, regularly use a high-efficiency, fast-acting lubricating system cleaner to clean the crankcase and maintain engine cleanliness. 2. Regularly remove carbon deposits from the car: Carbon buildup is inevitable during fuel combustion. Excessive carbon deposits can cause issues such as difficulty starting, unstable idling, poor acceleration, backfiring during rapid acceleration, excessive exhaust emissions, and increased fuel consumption. These have many adverse effects on the engine. To prevent carbon buildup, maintain good driving habits such as frequently driving at high speeds, appropriately increasing shift RPMs, avoiding prolonged idling, and using clean gasoline.
My car started shaking when accelerating to around 40 km/h, with the steering wheel wobbling back and forth. Based on my experience, this is most commonly caused by improper tire balancing, where the wheels don't rotate evenly. This is especially likely if you've recently changed tires or had a tire repaired but didn't get them properly aligned. Additionally, if the wheel rims have been damaged and slightly deformed, it can also cause shaking concentrated around speeds like 40 km/h. Loose suspension components can't be ruled out either, as wear and tear can amplify the shaking sensation. I recommend starting with the tires—take it to a repair shop for a balancing test. Spending a little money now can prevent bigger problems later. Definitely don't keep driving if the shaking is severe; it can distract you and increase the risk of a tire blowout.
During my driving experience, when the car shakes around 40 km/h, the core reasons are often wheel imbalance or drivetrain issues. Wheel hub runout or uneven tire wear can cause vibrations at specific speeds; problems with the driveshaft or half-shaft, such as worn universal joints, may also trigger mechanical resonance. Minor issues in the engine ignition system, like aging spark plugs, can worsen shaking during acceleration. I usually observe whether acceleration is smooth: if it only shakes around 40 km/h and stops after slowing down, it's tire-related; if the shaking persists, consider engine compartment issues. Don’t let small problems escalate—get a wheel alignment check promptly for safety.
