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Why Your Car Jerks When Slowing Down and How to Fix It?


Why Your Car Jerks When Slowing Down and How to Fix It?

All cars produce a bit of vibrating when you drive them, and that’s usually not a problem. However, if your car jerks while slowing down, that means you’ve got a serious problem on your hands.

Your car jerks when slowing down because there’s a problem with the engine or the transmission system. The transmission’s valve body is likely faulty and experiencing problems when downshifting gears. Besides that, the engine’s throttle body could be stuck, the ignition coil is malfunctioning, or the mass airflow sensor is defective, all of which undermine the combustion process and cause the jerking.

Read through this guide to understand which of those is causing your car to jerk while slowing down. Then, you can also discover how to fix the problem and restore your car’s functionality.

What Does It Mean When Your Car Is Jerking?

Firstly, it’s essential to understand whether or not your car is jerking. Learning what counts as jerking will make your troubleshooting much more effective. Plus, it’ll help you communicate better with your mechanic to explain the problem to them.

When your car jerks, it’s about how it feels rather than what noise it makes. You might recognize that jerking as shuddering, jolting, or vibrating excessively. But, no matter what you call it, they’re just different words to describe the same problem.

It’s only when the jerking is exceptionally intense that you might also hear some accompanying noises.

Whatever the case, car jerking is never a good sign, especially if it happens while you’re slowing the vehicle down. A car should only ever vibrate gently and consistently, so anything rougher than that points to a serious problem that requires your attention.

As you’ll learn in detail in the following section, a car that jerks when slowing down is likely experiencing a problem with its transmission or combustion system. Both possibilities require urgent troubleshooting and fixing, preferably by your mechanic or automotive technician.

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Why Does A Car Jerk When Slowing Down?

There are four reasons why your car jerks when slowing down. It’s like a problem with the transmission’s valve body, the engine’s throttle body, the ignition coil, or the mass airflow sensor.

This section will help you understand all four of those components, how they’re causing the jerking sensation you feel, and what you can do to fix them.

1. Faulty Valve Body

As you read earlier, a problematic transmission is one of the first causes of jerking when a car is slowing down. More specifically, the valve body inside the transmission is faulty and experiencing problems when downshifting gears.

The valve body is a crucial part of the transmission that channels fluid throughout the system. For example, as the car slows down, the valve body and its moving components will actively change the fluid flow to downshift gears.

Unfortunately, stuck valve solenoids or clogged pathways in the valve body can prevent that from happening. As a result, the transmission causes the car to shudder or jerk while it struggles to shift gears.

How to fix it: Firstly, you’ll have to remove the valve body from your car’s transmission to inspect it closely. That way, you can find out the root cause and solve it.

For example, you must replace stuck valve solenoids with new ones that can function correctly. Besides that, you must clear out any clogs so transmission fluid can flow smoothly when shifting gears, especially as the vehicle slows down.

For good measure, you’ll also want to drain the system and pour in fresh transmission fluid. That will restore optimal functionality to the valve body and stop your car from jerking.

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2. Stuck Throttle Body

The throttle body is an engine component that controls its intake of air. As you press down on the gas pedal, the throttle body will open proportionately to let air into the engine. That air will mix with fuel inside the combustion chamber to be burnt and converted into energy.

Given how much air it sucks in, the throttle body can suffer build-ups around its opening. When those buildups become severe, they can cause the throttle body to get stuck as it opens to specific positions.

Your car shudders because the throttle body tries to close as the vehicle slows down. However, it gets stuck and lets too much air into the engine, disrupting the combustion.

As a result, the engine shudders and jerks, causing you to feel those sensations throughout the vehicle.

How to fix it: Cleaning the valve body can often remove most of the buildup caught there. However, if the build-up is too severe or if the 

Read: Fuel Not Getting From Carb To Engine? What To Check And How To Troubleshoot It?

3. Malfunctioning Ignition Coil

Another component that’s related to the engine and its combustion process is the ignition coil. The ignition coil is an electrical transformer that supplies high voltages to your engine’s spark plugs.

When the ignition coil functions correctly, your spark plugs will have the power to generate sparks and keep the engine running. However, an ignition coil that malfunctions will fail to power one or more spark plugs, particularly at slower intervals (i.e. at lower vehicle speeds).

As a result, the engine will misfire, causing the car to shudder and jerk as you slow down.

How to fix it: The ignition coil is so crucial for the combustion process that you must replace it as soon as it malfunctions.

The new one will keep the spark plugs firing correctly, preventing the car from jerking at any speed.

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4. Defective Mass Air Flow Sensor

Lastly, consider the mass airflow sensor. It’s a sensor that measures how much air flows into the engine. Then, it supplies that data to the car’s computer to know how much fuel to mix with that air.

Unfortunately, a defective mass airflow sensor will send the wrong data to the onboard computer. That has been known to happen particularly when the vehicle reduces its speed and its intake airflow changes.

As a result, too much or too little fuel will be injected into the engine’s chambers, leading to misfires and other combustion problems.

As you’ve learned from the previous point, combustion problems will cause the whole vehicle to jerk due to the engine shuddering and jolting.

How to fix it: Firstly, inspect the mass airflow sensor. It could be dirty or loosely connected, causing the problems described above.

However, if the sensor is defective, you’ll have to replace it with a new one. Again, this is a critical component for the engine to function correctly, so you must never delay replacing it.

As soon as you get a new one in your car, the jerking will stop, and the engine will run smoothly.

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Final Thoughts

A car should never jerk if it’s in excellent working condition, especially not when it’s slowing down. However, jerking while slowing down does help narrow the problem down to specific issues in the engine and transmission.

For example, a faulty valve body, stuck throttle body, malfunctioning ignition coil, and defective mass airflow sensor could be to blame. Unfortunately, none of those problems is minor, which means they require immediate repairs or replacements.

The sooner you troubleshoot the problem and find the root cause, the quicker you can resolve it and get your car working correctly again.

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