Why does an automatic transmission car suddenly slow down during normal driving?

[GrahamAnn]

It could be due to a slipping torque converter or internal transmission clutches and brakes. Additional Information: Automatic Transmission: As the name suggests, it eliminates the need for the driver to manually shift gears. The vehicle automatically selects the appropriate gear based on driving speed and traffic conditions. A typical automatic transmission car has six gear positions, arranged from top to bottom as: P, R, N, D, S, L. Automatic Transmission Cars: Automatic transmission cars typically use hydraulic transmission devices to replace the mechanical clutch of manual transmission cars, hence there is no clutch pedal. When the engine speed is low, the torque transmitted by the fluid is limited and insufficient to propel the car forward. When the gear lever is placed in the drive position and the brake pedal is released, as the accelerator is pressed and engine speed increases, the transmitted torque increases, pushing the car forward.

[LaFinley]

Once when I was driving an automatic car, it suddenly slowed down, which was really scary. Upon reflection, it might be related to transmission issues. If the torque converter fails to lock, the engine will disconnect from the wheels, just like suddenly shifting into neutral, causing the speed to drop. If the valve body is clogged, the oil pressure becomes unstable, directly affecting the smoothness of gear shifts. A faulty control module can also cause problems, as incorrect signals from the computer can lead to the car slowing down naturally. If such a situation occurs in daily driving, it may be accompanied by shaking or unusual noises, so immediate inspection is necessary to avoid more serious damage. By the way, regular transmission fluid changes are crucial. Dirty fluid increases wear, so it's best to change it every 50,000 kilometers. For safety, if sudden deceleration occurs, immediately turn on the hazard lights, pull over, and check to prevent accidents. In short, don’t take it lightly—getting a professional diagnosis at a repair shop is more reliable.

[VanLeo]

When I encountered the sudden slowdown of my automatic transmission car, it was quite troubling. After analysis, it's often due to fuel system issues. For example, an aging fuel pump may fail to pump fuel properly, leading to insufficient pressure and fuel supply interruption. A clogged fuel filter can also restrict fuel flow to the engine, causing sudden power loss. Such problems are more common in older vehicles - my previous 10-year-old car had this issue before. For simple troubleshooting, you can listen for pump noises near the fuel tank or check if the car has difficulty starting. Using high-quality gasoline regularly helps reduce impurity buildup, and changing the filter every two years provides good prevention. For safety, don't panic and accelerate when slowing down - driving slowly to a gas station for inspection is more prudent. This perspective is quite practical, sharing it with everyone for more awareness.

[DiNolan]

My car's sudden automatic transmission slowdown made me think of ignition system issues. Spark plug erosion causing poor sparking, or ignition coil open circuit, can both interrupt cylinder ignition, leading to a sudden loss of power. Problems are more likely to surface during cold starts, such as engine shaking accompanied by speed drops. For self-inspection, you can remove the spark plug to check if the electrode is blackened or carbon-fouled, and replace it if necessary. As an enthusiast who enjoys DIY maintenance, I regularly clean ignition components to extend their lifespan. Safety tip: Avoid heavy throttle when decelerating as it can damage the engine; driving smoothly to the repair shop is the safest approach. Although this issue seems minor, it can lead to major failures, so early intervention saves money.