Reasons for a Car To Vibrate and Shake While Idling

In this article we are going to take a look at the concerning issue of excessive vibration and shaking while idling. We will look at the possible causes as well as some potential fixes for those issues. So read on to find out more about this worrying issue.

What Do We Mean by Vibration or Shaking?

When we start our cars in the morning we know there will be a certain level of noise and a certain level of movement as the engine runs. We get used to this so if the engine starts to sound labored or we have a rough idle it stands out.

If your vehicle is shaking more than normal or the vibration is more violent you can physically feel this. This is a sign that something is not quite right as there should be no logical reason for such a rough idling.

Causes of Vibrations and Shaking While Idling

There are a number of issues that may be causing excessive shaking to the car while the engine is idling. It may be the fault of several parts of your engine, some of which may be simple fixes while others are more complicated and potentially expensive.

Spark Plugs

One of the most common causes for excessive shaking from the engine is the spark plugs. You will have multiple of these in your engine, one on each of your cylinders. Their purpose is to ignite the compressed fuel/air mixture in the cylinders to drive the pistons.

When you are firing on all cylinders as the saying goes the engine should run smoothly. However, a worn out spark plug may not spark leaving the fuel/air mixture unignited. This results in what is called a misfire.

These misfires are most noticeable during idling when the car is at its most sensitive. You may hear a noise or even feel a shudder as a cylinder fails to ignite in its correct sequence. You may also get a check engine light coming on if there are spark plug issues.

These inexpensive parts should be replaced every 80,000 – 100,000 and are not difficult to replace for the amateur mechanic. If you have a misfire you will want to locate the spark plug at fault and fix it quickly. Driving with a constant misfire can do more damage to your engine and impact your fuel economy as well.

Vacuum Hoses

Most but not all modern vehicles use vacuum hoses to power the air and fuel systems. This helps to ensure the correct mixture of fuel and air makes it to the cylinders. If the mixture is not within a certain range you are at risk of combustion issues such as misfires.

Again you will feel these combustion issues in the form of vibrations and shaking while idling. This may be the result of a loose or broken vacuum hose that is no longer supplying the right amount of fuel or air to the cylinders.

This is a harder fix than the spark plugs but if you have the right skills and tools you may be able to repair the issue. The connections may just need to be tightened or replaced and any broken hoses should be switched out.

Broken or Loose Engine Mounts

If you were to examine the engine you would find that it is bolted into the engine bay. This is for obvious reasons so if one of these mounting points is loose or broken you can imagine this might be a problem.

The engine essentially has ongoing explosions happening in its cylinders while it is running so obviously this will cause movement. If it is securely bolted this movement is controlled, however, a loose engine mount may allow the engine to move around or jump.

Trust me if your engine is moving around you are going to feel that in the form of shaking and you will want to get this fixed. The parts are not expensive but as you have to lift the engine to get them replaced and the engine reattached it can cost a lot in labor.

Worn Out Belts

The processes of an engine are designed to be well timed and smooth. To help with this you will find the serpentine belt and the timing belt. If these become worn however it can make the engine run rough especially while idling.

As a result you may get vibrations and shaking as the engine struggles to compensate for the worn belts. These are generally easy to diagnose, especially the serpentine belt. This belt is big and stands out. A slight tug in the belt will tell you if it is loose and you should be able to see signs of wear.

The timing belt is a little harder to diagnose although if there is an issue with this you most likely will get a check engine light warning.

Fuel System Issues

In order to have a smooth running engine you have to ensure you have the right amount of fuel reaching the cylinders. As mentioned, issues with the fuel/air mixture can cause engine misfires and these can cause shaking and vibration.

Issues in the fuel system may include damaged or clogged fuel intake, fuel pump, fuel injectors and fuel filters. If any of these parts is the problem then fuel will not be getting to the cylinders efficiently and this will cause issues.

Once you know it is the fuel system you will then need to clarify which aspect is at fault. The best place to start is the fuel filter which may be clogged and simply by replacing this you can fix the problem. If this is not the cause you will want to move in and inspect the injectors, intake and pump.

Thankfully these issues will usually cause a check engine light to appear and record an error code in the vehicle's Electronic Control Module (ECM). This means you can use a scanner tool to read the codes and potentially pinpoint the issue.

Dirty Air Filter

As mentioned you need air and fuel in the right mixture so anything blocking the flow of air into the engine can lead to misfires and, as we have already learned by now, shaking. Generally speaking if the intake system is to blame the most common culprit is a clogged air filter.

This is a cheap and easy part to replace and by installing a new filter and resetting the code you may find that you have fixed the issue. If the problem persists however it may be something else intake related so you will need to look deeper for the solution.

Can You Ignore the Shaking?

The simple answer is no, you should never ignore excessive vibration and shaking while you idle. Whatever the cause this movement is your warning that the engine is not running smoothly and this can result in further damage.

Ignoring a cheap fix like a fuel or air filter can lead you to extensive engine damage and a huge mechanic's bill. Engine misfires are no joke they can really mess up your engine so never ignore these warning signs.

Conclusion

There can be a number of issues that can cause excessive vibration in your engine while idling many of which result in engine misfires. This shaking and vibration is not just annoying, it is a sign that the engine is in trouble and needs some attention.

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