Reasons for Jerking Sensation When Accelerating an Automatic Car

A jerking sensation when accelerating an automatic car is often caused by transmission issues, fuel system problems, or faulty sensors. The most common reasons include low or degraded transmission fluid, a worn-out torque converter, dirty fuel injectors, or a malfunctioning throttle position sensor.

1. Transmission fluid issues: Low or old fluid can cause rough gear shifts. Check the fluid level and condition—dark or burnt-smelling fluid needs replacing.
2. Torque converter failure: This component transfers engine power to the transmission. If damaged, it may cause shuddering during acceleration.
3. Fuel system faults: Clogged injectors or a weak fuel pump disrupt smooth fuel delivery, leading to hesitation or jerking.
4. Sensor problems: A faulty throttle position sensor or mass airflow sensor sends incorrect data to the engine control unit, affecting performance.

For example, a Vauxhall Corsa with a slipping transmission may jerk when accelerating due to low fluid. Similarly, a Ford Focus with dirty injectors might hesitate under load. Regular maintenance, such as fluid changes and injector cleaning, can prevent these issues. If the problem persists, a diagnostic scan is recommended to identify error codes.

There are four reasons for the jerking sensation when accelerating an automatic car: 1. The driver's habits are problematic; 2. Issues with the car's transmission itself; 3. Aftereffects of a loop machine oil change; 4. Incorrect amount of transmission fluid added. Below is a detailed explanation:

1. The driver's habits are problematic:

When driving, due to lack of proficiency, the gear selected may not match the vehicle's speed, causing the transmission to jerk.

For such cases, drivers should practice more to get accustomed to their car. Once familiar, the jerking sensation will reduce.

1. Issues with the car's transmission itself:

If the transmission does not dissipate heat in time, the temperature may rise excessively, leading to oil leaks and reduced oil pressure.

Drivers might not realize that the transmission relies on hydraulic oil to drive the clutch. If the hydraulic oil pressure is affected, a time lag occurs, which is one of the main reasons for transmission jerking.

1. Aftereffects of a loop machine oil change:

A friend's car experienced severe jerking after a transmission oil change, regardless of throttle input. The issue was resolved after cleaning the valve body. It is speculated that the pressure during the loop machine oil change dislodged impurities, causing valve body blockage and unstable oil pressure.

Changing automatic transmission oil is quite simple if done correctly. It is recommended to visit a reputable car maintenance chain for guaranteed oil quality and standardized procedures.

1. Incorrect amount of transmission fluid added:

If too much transmission fluid is added, the gears may churn foam, causing the oil pump to suck in foam and reduce oil pressure, leading to clutch slippage and jerking. If too little fluid is added, the oil pump may not circulate enough oil, also causing pressure drops and jerking. Some transmissions have overflow tubes inside the drain port. After draining old oil, do not rush to tighten the screw; continue adding oil until it flows out of the drain port.

Transmission fluid is closely related to jerking. If an automatic transmission is not maintained for a long time, the performance indicators of the fluid—such as lubricity, viscosity, and thermal stability—will significantly decline.

Especially regarding transmission fluid temperature, if the radiator is dirty and heat cannot dissipate, the computer will detect high temperatures and enter emergency mode, forcing upshifts (locking into a specific gear). This can cause the car to struggle when accelerating, with dragging and jerking sensations. When oil temperature exceeds 135°C, it can severely damage friction plates and clutch components.