What Causes Low-Speed Jerking?

[RileyAnn]

Transmission jerking is the impact sensation caused by the inertia of moving parts inside the engine. Below are the reasons for engine jerking: 1. Causes of engine jerking: During the process where the engine speed is either increased or decreased, if not handled properly, sudden changes in engine speed during gear shifts can cause the inertia of the engine's moving parts to react against the vehicle body. 2. Low-speed jerking: Many drivers experience this issue. When driving at low speeds, the gear frequently shifts between first and second, and the clutch repeatedly engages and disengages. If power transmission cannot be smoothly completed within a short time, common low-speed jerking occurs. Jerking sensations are normal during startup and low-speed driving, usually due to turbocharger engagement at low RPMs, which affects engine speed. 3. Upshift jerking: This is mostly caused by the transmission's response speed being insufficiently fast. The upshift speed cannot keep up with the throttle input, so the jerking sensation occurs at the moment of gear shift. 4. Downshift jerking: This is mostly due to the intervention of the energy recovery system. Once the driver releases the throttle pedal or presses the brake pedal, the generator immediately starts working, placing additional load on the engine. This affects the engine speed, causing it to be out of sync with the clutch plate speed, resulting in a jerking sensation.

[CourtneyLee]

Yesterday while repairing a car, I just dealt with one that had severe jerking issues. I found that low-speed jerking problems are usually related to three aspects. First is the fuel system—clogged fuel injectors can cause unstable fuel supply, especially common in older cars. Second is the transmission fluid; when the fluid hasn't been changed for 70,000 to 80,000 kilometers, the clutch plates are prone to slipping. Additionally, sensors like the mass airflow sensor, if coated with sludge, can cause the ECU to misjudge the air intake, leading to jerking. I recommend checking these three areas first—in my experience, 80% of such cases are due to these reasons.

[VanCharlie]

As someone who frequently tinkers with used cars, low-speed jerking is most likely caused by carbon buildup. Excessive sludge in the throttle body makes it less responsive, carbon deposits in the intake manifold affect the air-fuel mixture, and worst of all, spark plugs coated with carbon cause unstable ignition. Last week, I worked on an old Buick Regal with 100,000 kilometers—after cleaning the carbon deposits inside the cylinders, it felt like a whole new car. Also, fuel quality does make a difference; lower-grade 92-octane gasoline from small gas stations often contains more impurities, which can clog the fuel filter.

[VonCharlotte]

This issue depends on the transmission type. Manual transmission jerking is mostly caused by worn clutch components, especially when the clutch is partially engaged, shaking like a sieve. Automatic transmission issues are often due to valve body failures, such as Audi CVT belt slippage or Volkswagen DSG shifting logic confusion. My American car used to jerk too, but it became smooth immediately after changing the transmission fluid. Electronic throttle initialization can also help—just disconnect the power for five minutes and restart to let the computer relearn.

[GenesisFitz]

Have you noticed the RPM range where the jerking occurs? Sudden jerks around 1500 RPM are usually caused by turbo lag, especially in small-displacement turbocharged cars. Engine mount deterioration is also quite common—I once fixed a 5 Series that made a clunking sound over speed bumps, and replacing the engine mounts completely solved the issue. If the jerking is particularly noticeable during cold starts, checking the high-pressure fuel pump's pressure value is definitely the right move. Also, don’t overlook the transmission mount; if this rubber component collapses, even gear shifts can feel shaky.