Why Your Car Jerks When Stopped

So you’ve noticed your car jerking when stopped. Maybe you were slowing down as you approached a red light or pulling up your driveway towards your garage when suddenly, right as you stepped on the brakes, the car jolted.

Possible Causes Why Car Jerks When Stopped

So, what causes a car to jerk when stopped? The truth is it’s a jarring experience with a number of possible causes, including the following:

Faulty Transmission

First on the list of potential suspects is an issue with the transmission system. The transmission connects your car’s engine to its wheels and handles gear shifting. A faulty transmission won’t shift gears as smoothly as normal, which can cause bumps and jolts as you slow down to park. There are a few reasons your transmission might be acting up in this way.

Dirty Transmission Filter

A transmission filter keeps contaminants in transmission fluid from entering the transmission pump and getting distributed throughout the entire transmission system. When the filter is clogged, the pump isn’t able to siphon enough fluid, resulting in low fluid pressure in the system. This also leads to slips and jerks as you shift gears.

Low or Contaminated Transmission Fluid

Transmission fluid lubricates, cleans, and cools the different parts of the transmission system. If your transmission fluid is low, the transmission can slip, causing your car to jerk as you shift gears to come to a stop. Contaminated transmission fluid also causes slippage as well as a loss in hydraulic power.

Bad Torque Converter

If your car jerks when stopped in drive on your automatic gear shift, the torque converter might be to blame. The torque converter and torque converter clutch do the same job in an automatic transmission as the clutch does in a manual transmission. The torque converter keeps the engine from stalling when your vehicle stops and increases the engine’s pulling power when needed. It’s a delicate balance, and if the converter is acting up, your car might shudder at different speeds.

The torque converter and torque converter clutch do the same job in an automatic transmission as the clutch does in a manual transmission.

–Anthony Harlin, ASE Certified Master Automobile Technician

Bad Shift Solenoids

Shift solenoids activate the transmission’s hydraulic circuit and control fluid flow to shift gears in your automatic transmission. When they activate or deactivate incorrectly, the gears don’t shift properly and your car can jerk when you shift gears.

Bad Speed Sensor

A malfunctioning speed sensor in your automatic car can also cause the car to jolt while stopped. The speed sensor’s connected to the transmission shift solenoids. It lets them know when the car needs to shift gears. If the speed sensor isn’t working properly, then it might send flawed messages to your vehicle’s powertrain control module (PCM), leading the engine to jerk or vibrate when your car stops.

Faulty Brakes

Brake system issues can also lead to your car jerking when coming to a stop. The brakes have a number of components that can trigger this problem. Here are some possible culprits:

Brake Disc Deformation

Brake discs, which are also known as rotors, are in charge of decelerating your car using brake torque. These discs need to be replaced periodically to remain functional and safe. Over time, using your brakes wears down the discs unevenly, leading to shuddering or pulsing when braking. This is a sign that the discs need replacing.

Seized Brake Calipers

Calipers squeeze the brake pads against the rotors to trigger the wheel brakes. If one of the calipers is rusty, worn, or damaged, it can potentially seize. This causes the brake to drag as the caliper catches one of the wheels without releasing it. When a caliper drags like this, it’s also referred to as a frozen or sticky caliper. A resulting jolt accompanies this uneven braking.

Anti-Lock Brakes Not Working

The anti-lock braking system (ABS) in your car detects when a wheel has stopped rotating while your car is still in motion. It relays this information to the car’s computer, which adjusts the brake fluid pressure to prevent the lock. When the ABS isn’t working properly, it can cause your brakes to act strangely, including jolting your car when stopped.

Faulty Ignition Coils or Coil Pack

The ignition coil provides timed, high-voltage sparks to your engine’s spark plugs. A damaged or faulty coil pack can result in engine misfires at low speeds or when you stop, which will cause your car to jerk.

If you’ve noticed that your car jerks when coming to a stop, it’s likely you’ll have a hard time diagnosing the exact cause. With a long list of possible causes, it’s best to visit a mechanic to find out the main reason behind this odd behavior.