What causes two jerks three seconds after releasing the throttle?
3 Answers
Jerking after releasing the throttle could indicate an issue with the transmission. It's advisable to check if the transmission fluid is low or has deteriorated. If the transmission fluid is fine, it's recommended to visit a professional repair shop or a 4S dealership to have the transmission control system inspected. Generally, when the engine speed and vehicle speed just meet the gear-shifting criteria at low speeds, the upshift jerk can be more pronounced. If the throttle is slightly larger, making both engine speed and vehicle speed significantly exceed the shifting standard, the gear-shifting jerk will be less noticeable. For manual transmission cars, jerking during throttle application and gear shifting is largely a matter of driving technique, often due to uncoordinated clutch and throttle operation or releasing the clutch too quickly when starting. The main issue with manual transmission cars occurs during downshifting. Many beginners often fail to shift gears correctly when decelerating and downshifting, causing gear dragging which results in vehicle jerking.
After driving for so many years, I've encountered the issue of jerking after lifting off the throttle several times. Especially in traffic jams, about three seconds after releasing the accelerator, it feels like the car is being pulled back and then jerks again, which really affects driving comfort. This is usually because the spark plugs are too severely carbon-fouled or the ignition coils have aged, causing unsteady ignition at the moment of lifting off the throttle. If the engine RPM drops too quickly, it's easy to experience that double jerk. The fuel injection system might also be problematic—for example, clogged fuel injectors or unstable fuel pressure can disrupt the air-fuel mixture ratio, making it more noticeable at idle. Additionally, for automatic transmission cars, faulty shift logic in the transmission can cause delayed responses, such as slow torque converter engagement after lifting off the throttle due to wear. It's recommended to first check the spark plugs and ignition system to see if they need replacement, while also using a diagnostic tool to read any fault codes and ensure the engine control unit isn't set abnormally. If the problem persists, it's best to have a professional auto repair shop diagnose it—don't tough it out, as prolonged driving like this can damage the engine and waste fuel.
I find this kind of jerking sensation three seconds after lifting off the throttle extremely annoying. My car did this last time—it hesitated for a few seconds after releasing the gas pedal before jerking twice, as if being kicked. Based on my car enthusiast experience, the most common cause is sensor issues, such as a dirty or faulty throttle position sensor or mass airflow sensor, where inaccurate signals lead to delayed engine response. Worn spark plugs are also a major suspect, as improper ignition timing disrupts the engine's rhythm. Additionally, excessive carbon buildup in the intake manifold can obstruct airflow, causing improper air-fuel mixture adjustment after lifting off the throttle, leading to engine stalling and then regaining rhythm, resulting in jerking. Another possibility is a software bug in the engine control module, requiring a trip to the dealership for a firmware update. You can check the spark plugs for blackening or inspect the ignition coils for cracks yourself, and use an OBD scanner to check for trouble codes. For older cars, a clogged fuel filter can also cause insufficient fuel supply. Regular throttle body cleaning or replacing the filter can effectively prevent such minor issues.
