Why Do I Feel Vibration When Idling in the Car?
4 Answers
The reasons for feeling vibration when idling in the car are as follows: 1. The most common reason for feeling slight vibration when idling in the car is a dirty throttle body or excessive carbon buildup in the fuel injectors. When there is too much carbon buildup inside the engine, the gasoline sprayed by the cold-start fuel injector will be largely absorbed by the carbon deposits, resulting in a lean air-fuel mixture during cold starts and making it difficult to start. The gasoline adsorbed on the carbon deposits will then be sucked into the combustion chamber by the engine's vacuum, enriching the air-fuel mixture. This fluctuation between lean and rich mixtures causes idle vibration after a cold start. 2. Check the condition of the spark plugs, high-voltage wires, and ignition coils. Poor performance of the ignition system or weak spark from the spark plugs can also lead to such issues. The solution is to check if the spark plugs have excessive carbon buildup and replace them if necessary. 3. If you have already cleaned the engine carbon deposits, cleaned the throttle body, replaced the oil pads and spark plugs, but still notice body vibration during idle, it is recommended to visit a 4S shop to check the fuel supply pressure and the intake pressure sensor. Abnormal fuel pump pressure or incorrect readings and poor performance of the intake pressure sensor can also cause body vibration. 4. Car vibration can also be related to aging engine mounts. Engine mounts are essentially the shock absorption system of the engine, responsible for absorbing minor vibrations during engine operation. If the engine mounts are faulty, these vibrations will be transmitted to the steering wheel and the cabin, causing vibration during idle.
I've been driving for over a decade and have seen plenty of idle vibration issues. The most likely culprit is the aging and cracking of the engine mount rubber pads. After all, they bear the heavy load of the engine day in and day out, and over time, they just can't take it anymore. At this point, vibrations travel directly from the chassis into the cabin, feeling like a phone vibration amplified several times. Another common issue is carbon buildup in the throttle body. With frequent city traffic jams, the fuel system tends to accumulate impurities, which is like the engine struggling to breathe, naturally causing severe shaking. Spark plugs are also a key point to check, especially after tens of thousands of kilometers of use. Insufficient ignition energy can lead to intermittent operation in individual cylinders. Another sneaky culprit is the AC compressor. During summer, when idling at a red light with the AC on, the sudden power draw when the compressor kicks in can cause the engine to jerk. I recommend starting with the mounts and throttle body—these are the usual suspects we veteran drivers always talk about.
As a regular car owner, I panicked when I encountered this issue last year. At first, I suspected the engine might be failing, but later at the repair shop, I learned: there are four engine mounts underneath, acting like shock absorbers to dampen vibrations. These rubber components start to deform and crack after five or six years, and once they lose elasticity, vibrations directly transmit into the cabin. The mechanic used a flashlight to show me, and sure enough, there were cracks. Another time, during a car wash, a worker pointed out carbon buildup in the throttle body. He explained that since I mostly drive short distances in the city, incomplete fuel combustion leads to carbon deposits, similar to grease buildup on a stovetop. At idle, insufficient air intake causes rough idling. Now, I regularly check the condition of the engine mounts and clean the throttle body every 20,000 kilometers, and the vibrations have noticeably reduced. By the way, using low-quality fuel can also cause shaking, so I recommend trying a reputable gas station.
The answer depends on the situation. Slight shaking during cold starts is normal and can be ignored if it disappears after warming up. Persistent shaking requires checking the engine mount rubber pads, as aged rubber loses its cushioning effect completely. Next is carbon buildup, mainly accumulating in the throttle body and fuel injectors, obstructing smooth air and fuel flow and causing unstable combustion. Another common issue is faulty ignition coils, especially in older vehicles, leading to intermittent misfires in individual cylinders. Tire factors are often overlooked; if there's a significant difference in pressure among the four tires or slight wheel rim deformation, abnormal vibrations can be felt through the steering wheel at idle. The simplest self-check method: first replace the fuel filter to rule out fuel quality issues, then sequentially inspect the engine mount rubber, spark plugs, and tire condition.
