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What To Do If Your Car Shakes at Idle but Smooths Out While Driving?

car shakes at idle but smooths out while driving

Many drivers face a situation when their vehicle does not shake while driving, but they feel the vehicle shaking when it is in an idle situation. No need to feel panic because this is not any severe or uncommon car issue. Sometimes you experience a smooth drive but inappropriate shaking in busy city stoplights. You can consider many things as a reason for this problem. But first, a user should pay attention to the problems carefully. The car can shake because of low revs, or it can struggle physically. Sometimes you can press the throttle paddle slowly to give the engine enough power to tick up. But what are the reasons behind this problem, and what can you do if the car shakes at idle but smooths out while driving?

Let’s dive into the details of this critical situation and learn how to fix it.

What Are the Reasons If Your Car Shakes at Idle but Smooths Out While Driving?

why does my car vibrate on idle

Because of many car part issues, a user can face this situation. You can go to a professional mechanic to get it diagnosed. But as the owner of your vehicle, you should also know the reasons why your car shakes at idle but smooths out while driving. Here are some reasons that can end up with this problem.

A Loose Gas Cap:

This is one of the most common and easy-to-recognize reasons. A loose gas cap can cause a rough idle situation by creating problems in the air intake process. It can cause an air leak as a result; the engine has to work harder. Not only a loose gas cap but if there is carbon build-up inside the gas cap also can create an issue. It evaporates some of the fuel that should be burnt. This makes the combustion process difficult for the car. Especially you may face while starting the car. Gas cap replacement can cost you up to $300.

Damaged Throttle Sensor:

A failing throttle sensor creates this type of issue. A faulty throttle sensor cannot determine if the car is moving or not. That means the engine tries to increase the speed continuously. Too tight throttle cables can cause damage to the sensor as they cannot work to their full potential. The throttle sensor can also create a problem, just like a loose gas cap, as the air passes through an ineffective seal. A new throttle sensor costs around $150-$200.

Air Control Valve:

An Air control valve controls the air entering the engine at idle. If it gets into a fault, your car’s engine will not get enough oxygen to burn all the fuel in the tank. It also contains a vacuum that is controlled by the engine vacuum. If that does not work, the car will continue with an irregular idle because of the absence of a vacuum.

Also, a faulty accelerator position sensor can also cause a rough idle if it can’t determine the pressing time of the accelerator. That means the vehicle’s engine will want to run fast even when it should be in a smooth idle situation. A faulty air control valve comes in the way of giving an idle to the passenger.

Damages Oxygen Sensor:

An oxygen sensor controls the amount of oxygen inside the engine so that the combustion does not get disturbed. This is an important car part because your car relies on the computer data of the optimal air and fuel ratio. That is why a faulty oxygen sensor cannot determine what level of oxygen should be in the engine compartment. You may face a car shaking problem when it is idle because of this sensor. A new oxygen sensor costs you around $150-$450.

Battery Cables:

All of your car’s electrical components are connected to the battery through a lot of cables. If any of the cables is loose, then it can cause less power. As a result, your car can create a rough idle or a problem starting. The vehicle can even refuse from getting refused. In such cases, you should check all the electrical components and the connections first.

These are some most common and foremost reasons why your car roughs idle but drives smoothly.

How Can You Diagnose and Solve This Issue?

For a solution, you can normally go to a professional mechanic who can diagnose the car from every angle. Or, as some homemade remedies, you can follow these tips:

  • First, you can clean the throttle sensor with an aerosol cleaner. It will remove any restriction from flowing air to the engine.
  • Secondly, you can also check whether the battery cables are properly connected or not. If there is any electrical misconnection, you may face a rough idle.
  • A faulty crankshaft position sensor can cause this problem. So better you replace any faulty part with good quality OEM parts.
  • Inspect all the engine hoses to find out if there are any cracks, vacuum, or any other fault.

On the other hand, if you are facing this issue and still cannot rectify the reason, then other signs can help you that are related to this problem. They are:

  • Engine misfires quite often.
  • Engine mounts start to beak.
  • Fuel Intake gets clogged up.
  • Dirty or damaged spark plugs.
  • Issues with the throttle body.
  • Air-intake issues.

You May Also Like To Read: Car Wobbles When Hitting Bumps


Why does my car shake when idle but not when driving?

There can be several reasons behind this situation. But the most prominent reason is a loose gas cap. Because of the loose gas cap, the air intake process gets clogged, and the combustion process gets disturbed.

What causes a car to vibrate when idling?

A vehicle’s engine mounts hold the engine attached to the car. A broken or damaged engine mount cannot hold the engine tight and creates a vibration at idle.

Can a bad spark plug cause shaking at idle?

Damaged or broken spark plugs cause an uneven burn of fuel. It can show the result in fluctuating RPM and louder noise. This is why you can observe vibrations at idle or at low speed.

What is shuddering in a car?

Due to various reasons, a shuddering situation can get created from the engine compartment. If the engine does not have the proper amount of air, fuel, or spark, a user can feel vibrations in the cabin.

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