Key Takeaways

  • Faulty spark plugs, clogged fuel filter, or transmission issues can be the issue.
  • A vacuum leak, brake issues, or a faulty throttle position sensor could be the issue.
  • How to change and clean spark plugs are outlined in this article.
  • Check your brake lines when doing a brake inspection.
  • Use brake clean to check for a vacuum leak.

Lots of times, cars can do some funny things when decelerating. But what is going on when your car jerks when slowing down?

There are a number of different reasons your car can do this. Faulty spark plugs, clogged fuel filter, transmission issues, vacuum leak, brake issues, or a faulty throttle position sensor can cause this issue.

I’m a mechanic with five years experience of diagnosing and repairing vehicles. I received my training at an accredited college that led me to get my associates degree in automotive repair. I receive regular training on the latest automobile technologies.

Table of Contents

Causes

If your car is jerking when you slow down, it could be for a number of reasons. Let's look into the reasons as to why this could be.

  1. Dirty or faulty spark plugs: If the spark plugs are dirty or faulty, they may not provide the required spark for the combustion process. This incorrect or weak spark can cause the engine to misfire and the car to jerk when slowing down. To fix this, you can replace the spark plugs or clean them if they are dirty. This may relieve a car jerk problem when slowing down if the problem is dirty or faulty spark plugs.
  2. Faulty Fuel Injectors: If the fuel injectors in a car are bad or you have dirty fuel injectors, this can cause the car to jerk when slowing down.
  3. Clogged Fuel Filter: If the fuel filter is clogged, it can restrict the flow of fuel to the engine. This restriction in the fuel filter can cause the car to jerk when slowing down. To fix this, you can replace the fuel filter.
  4. Transmission Issues: If the automatic transmission is slipping or shifting incorrectly, it can cause the vehicle to jerk when slowing down. To fix this, you can have the transmission fluid checked or the whole transmission checked and serviced by a professional mechanic.
  5. Vacuum Leak: A vacuum leak can cause the car to jerk when slowing down as it affects the air fuel mixture. To fix this, find the vacuum leak and repair it.
  6. Brake Issues: If the brakes are worn or damaged, it can cause the car to jerk when slowing down. To fix this, have the brakes inspected and replaced if necessary.
  7. Faulty Throttle Position Sensor: If the throttle position sensor in the throttle body is faulty, it can cause the car to jerk when slowing down. To fix this, you can replace the throttle position sensor.

It is essential to have a professional mechanic diagnose and fix any issues with your car to ensure that it runs smoothly and safely.

Car Jerking When Slowing Down

The car jerking can also be due to a number of other things. For example, if your air intake is leaking, this can cause a vacuum leak, causing the car to jerk.

To remedy this, check the air intake system by spraying brake clean around the seals of the intake system. If the engine starts to accelerate when you spray brake clean around a certain area, it thinks this brake clean is fuel.

That means a vacuum leak is occurring where you are spraying and should be fixed as soon as possible.

If you have a faulty transmission, this can also cause the issue. The first place to check a transmission system is by checking the transmission fluid.

Brake lines can also be the issue, since if they are leaking, it can cause uneven braking pressure causing the car to jerk when slowing down.

If your mass airflow sensor is bad, this can mimic the issues of a vacuum leak. Mass air flow is directly related to vacuum, so make sure the sensor is operating properly.

The bottom line is, if you don’t know your way around a car, and can’t diagnose this issue yourself, it’s best to bring it to a mechanic. The problem could be relatively simple, or very complicated.

Pay the diagnostic fee, and if it’s a simple problem, fix it yourself.

Changing and Cleaning Spark Plugs

Changing spark plugs is a relatively easy job. While you can run into some roadblocks, the process is straightforward. To change spark plugs, the first thing you're going to need is a spark plug socket.

If you are experiencing problems with your engine, one possible cause could be dirty spark plugs. In this case, you may need to remove and clean the spark plugs. Here's a step-by-step guide on how to remove and clean spark plugs:

  • Check your car's owner's manual to determine the correct type of spark plug for your engine.
  • Make sure your car engine is cool to the touch. It's best to work on the engine when it's not hot, as the heat can cause burns.
  • Locate the spark plugs. They are usually located on the top of the engine and are attached to the spark plug wires.
  • Remove the spark plug wires by gently pulling the boot straight off the spark plug. Be careful not to pull on the wire itself, as this can damage the wire or the connector.
  • Use a spark plug socket and a ratchet wrench to remove the spark plug. The spark plug socket has a rubber insert that grips the spark plug, allowing you to remove it without damaging it. Turn the ratchet wrench counterclockwise to loosen the spark plug.
  • Inspect the spark plug for signs of wear or damage. If the electrode or the porcelain insulator is damaged or worn out, you'll need to replace the spark plug.
  • If the spark plug is dirty, you can clean it using a wire brush or a spark plug cleaner. Be careful not to damage the electrode or the porcelain insulator.
  • Check the gap on the spark plug using a gap tool. The gap should be set to the specifications in your car's owner's manual. If the gap is too large or too small, you'll need to adjust it using the gap tool
  • Once the spark plug is clean and properly gapped, you can reinstall it using the spark plug socket and ratchet wrench. Tighten the spark plug by turning the ratchet wrench clockwise until it is snug.
  • Finally, reattach the spark plug wires to the spark plugs. Make sure the boots are securely attached to the spark plugs, as loose connections can cause misfires.

In conclusion, removing and cleaning spark plugs is a simple process that can help keep your engine running smoothly. If you're not comfortable working on your car's engine, it's best to have a professional mechanic handle the job.

Car Jerks When Slowing Down (Causes & Fixes)

About The Author

Christopher Sparks

Christopher Sparks

Christopher Sparks has been servicing vehicles since 2012. After completing the automotive studies program at Camden County College, he was awarded an Associates's Degree in Applied Science. His first job was a lube-tech at Jiffy Lube, and is currently an independent B-Technician servicing vehicles for the United States Postal Service. Christopher is ASE certified and loves rebuilding engines.

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