Car Shakes When Accelerating But Not When Coasting

Are you wondering why your car shakes when you step on the gas? You may have also noticed that the shaking suddenly disappears once you lift your feet off. Why is this happening? Should you look closely and immediately into why your car shakes when accelerating but not coasting?

If your car shakes while accelerating but not when coasting, there could be several reasons for it. Here are some of the common reasons why this might be happening:

  1. Faulty or Damaged Inner CV Joints
  2. Damaged Engine Mounts
  3. Unbalanced Tires
  4. Loose Tire Lug Nuts
  5. Bent Driveshaft
  6. Bent Axle
  7. Shattered Wheel Bearings
  8. Stuck Brake Caliper
  9. Damaged or Disconnected Vacuum Hose
  10. Worn-out or Just Dirty Sparkplugs
  11. Improper Wheel Alignment

Read on to learn more about why your car shakes when accelerating only but not when coasting. You will also know why you should have it looked at as soon as possible.

Why Does My Car Shake When Accelerating but Not When Coasting?

why does my car shake when accelerating but not when coasting

One of the scariest things that you can experience is your car suddenly shaking while driving down the highway. If you cannot regain control of your vehicle as soon as possible, you may get into a severe accident.

Here is the issue: why is it that there is only vibration when accelerating but not coasting? There are quite a few reasons why this is happening. Here are just some of them:

1. Faulty or Damaged Inner CV Joints

The constant velocity joint (CV) is at the end of each wheel axle. There is an outer and an inner CV joint. The inner CV joint is the one connected to the wheel. The job of the CV joint is to transfer the power from the drive shaft into the drive wheels.

The CV replaced the outdated U-joint used before in older vehicles. The CV joint makes use of different gears.

Doing that ensures that all wheels turn at a constant velocity, hence the name. You can turn corners at relatively high speeds without the rear wheels fishing.

The typical damage to CV joints is from tearing the protective rubber boot. The rubber boot protects the CV joint against water and mud from the road. If the boot tears, the CV joint can get corroded, lose lubrication, and eventually get stuck.

As the damage to the CV joints worsens, the minor vibrations can turn into violent shaking when put under stress. One instance is when you step on the gas. Once the CV joint gets damaged, it can be almost impossible to fix. The only option, therefore, is to replace the entire thing.

2. Damaged Engine Mounts

As the name suggests, engine mounts hold the car’s engine on the vehicle’s frame. However, they also serve another purpose – that is, dampening the vibrations coming from the engine. Without proper motor mounts, you and all your passengers will be shaking along with the engine.

Engine mounts consist of a hard rubber material. This is the reason why they can dampen the strong engine vibrations. When there is damage in even one motor mount, you will have to deal with the excess vibrations.

However, the engine will also shake itself apart. Also, if one engine mount breaks, the others must pick up the slack. The added stress will make them break eventually as well. When the entire car shakes upon stepping on the gas, one reason could be a broken engine mount or two.

3. Unbalanced Tires

Did you recently replace your tires and notice your car’s slight shaking when driving at highway speeds? Does this happen even if you are not stepping on the gas? Then the probable culprit could be unbalanced tires.

Although tires look symmetrical all the way around, you can’t expect them to be perfectly balanced. Some spots have thicker rubber, which is why they weigh more.

A professional tire installer will mount your new tires on a balancing machine to fix this issue. The installer will also install tire weights inside the tire to balance the overall weight.

You might not notice anything wrong with unbalanced tires driving at slow speeds. However, once the tires spin at highway speeds, the uneven weight of the tires will be apparent. The shaking will not be quite as strong, but it can still be annoying.

Bring your car back to the tire installer and ask them to balance your tires. If the shop is truly professional, they will do this for free. They would be at fault because they should have done it beforehand.

4. Loose Tire Lug Nuts

Loose tire lug nuts are simple and common problems. However, this could lead to a catastrophic failure if not addressed immediately. It is necessary to torque the lug nuts that hold the wheel in place properly. They should also be checked regularly if they loosen over time.

When there is a loose lug nut, it would feel like the car is shaking. The reason behind this is the wheel wobbling. If left unattended, the loose lug nuts would fall off.

This would then lead to the wheel studs getting shorn off by the torque of the wheels. Your wheel could, therefore, fly off your car and cause a potentially fatal accident.

You can use a regular torque wrench to check if your car’s lug nuts are loose. This can help ensure that you get to tighten each one based on the manufacturer’s specifications.

5. Bent Driveshaft

Are you driving a rear-wheel drive (RWD) vehicle? Then it is highly likely that the power coming from the engine goes through the driveshaft or the propeller shaft. Even if there is a slight bend in the driveshaft, you will still feel the car shaking. The reason is that it is spinning at such a high rate.

At low speeds, you will be feeling a bit of vibration. However, as the car goes faster, the drive shaft’s slight bend becomes apparent.

You may start noticing your car starting to shake, and it gets stronger the faster you go. In that case, you should have your driveshaft checked by a professional mechanic.

If the mechanic confirms that you have a bent driveshaft, your only option is to get a replacement. You do not simply heat a driveshaft and bend it back into shape. This may only weaken the metal, thus making it even more dangerous.

6. Bent Axle

Everything may seem fine if you accidentally drove over a curb or a large rock. The same is true if you figured in a slight fender-bender.

However, later, you notice that your ride is no longer as smooth as it once was. If that happens, you should get your front and rear axles checked immediately.

Similar to when you accidentally bent your driveshaft, the faster a bent axle spins, the stronger the vibrations it produces. Another similarity to the bent driveshaft is that you can only replace a bent axle when that happens. Repairing it is not an option.

7. Shattered Wheel Bearings

engine shakes when accelerating but not when coasting

Do you hear a noise from your wheels while driving aside from the shaking? This could indicate a broken or worn-out wheel bearing. This issue can be a huge problem later if you do not address it quickly enough.

The wheel bearing ensures that your wheels are spinning smoothly on the axles. In case of damage, it would cause a lot of friction. This could further lead to severe damage later. In some of the worst cases, the wheel would start wobbling when spinning at high speeds.

Again, why does my car shake when accelerating but not when coasting? If your car shakes when accelerating but not coasting, it might be due to a faulty CV joint, bent axles, damaged engine installations, unbalanced tires, or worn wheel bearings.

8. Stuck Brake Caliper

What if you have a faulty brake caliper stuck while still in contact with the rotor? It could be the cause of the unwanted vibrations. In this situation, you will mostly feel the vibrations through the steering wheel.

If the stuck caliper continues to pinch on the rotors, the vibrations will worsen the faster you go. Also, when you stop or slow down, you will get a whiff of what smells like burning rubber and metal. This is the smell of your stuck caliper burning because of all the friction it caused.

If caught early enough, the only components that you might need to replace are the brake pads. However, it could be exceedingly worse.

The caliper could seize and cause the wheel to lock. This can be very bad when you are on the highway. When this happens, you might need to replace the entire brake assembly.

9. Damaged or Disconnected Vacuum Hose

A disconnected vacuum hose may cause strong shaking of the entire car. It can also lead to your engine stalling. This can be quite dangerous if your car stalls in the middle of the freeway.

A torn or damaged vacuum hose cannot retain a vacuum. This can cause various sensors all over the car to fire up, thereby confusing the onboard computer.

What this means is that it can cause the engine to backfire. It can also lead to misfires, loss of a considerable amount of power, and other issues.

Pop the hood and check if all the rubber hoses connect to where they are supposed to be. If you find even one disconnected hose, figure out where it needs to go and plug it back. You may need to use one of those metallic collars to keep the hoses in place.

The immense pressure produced by vacuum hoses in turbocharged cars makes them prone to loosening and potentially coming off. As such, it is advisable to replace damaged hoses immediately with stronger silicone ones.

10. Worn-out or Just Dirty Spark Plugs

A fouled-up spark plug can cause the engine to misfire. This means that its corresponding cylinder will not have a spark to ignite the fuel.

Ideally, you should replace your spark plugs every 80k to 100k miles. If you can no longer remember the last time you replaced your spark plugs, it is probably time to do so. At the very least, you should clean the spark plugs if you cannot replace them.

Misfiring cylinders due to faulty spark plugs can cause the engine to lose its balance. This will then result in it vibrating stronger than usual. Also, you will feel that the car is not as powerful as it usually is.

11. Improper Wheel Alignment

Another probable reason your car is shaking while driving is improper wheel alignment. This means that the wheels are bowed in (toe-in) or out (toe-out) too much. Imbalanced wheels will wobble or hop up and down, which causes the entire car to vibrate.

You can tell if you are dealing with imbalanced wheel alignment by checking your tires for uneven wear. If the outside edge of the tread already gets worn down, you have too much toe in. If the opposite is true, you have too much toe out.

To fix this issue, take your car to your nearby tire center. They usually have wheel alignment services.

What Are Other Causes of a Shaking Vehicle?

There are also other situations wherein you will notice your car shaking. Here are a couple of possible scenarios and what could be causing them:

1. Climbing Steep Hills

It could be that your car starts to shudder and slow down when climbing steep hills. In that case, one possible reason is that your car is not powerful enough to push itself uphill. Another reason is you are in the wrong gear.

If the problem lies in your car being severely underpowered, you do not have to get a more powerful vehicle. One thing you can do, instead, is to lessen the load it carries. For instance, you should not load passengers to full capacity.

You can also add modifications to your car’s engine. That way, it can push out much-needed additional horsepower.

What if you are driving a stick shift, and your car still shakes when climbing hills? The problem might be that you are in the wrong gear. If the hill is steep, place the shifter at a lower gear.

Depending on the hill’s steepness, I would usually use the second gear to climb. You may not be going any faster, but it can lessen the engine vibrations. Your car is also inching up towards the crest of the hill.

2. Idling Vehicle

Does your car shake quite often, even if you are not stepping on the gas? One possible reason could be that your vehicle is in dire need of a tune-up. It is, therefore, necessary to bring your car to the mechanic. They will use a diagnostic tool to figure out if other things might be wrong with your car.

Usually, there would be a need to change the oil and replace the sparkplugs to solve the problem. Another thing that mechanics may check is the transmission.

One reason your car is shaking while idling is an issue with the clutch plate. If you are unlucky enough, the entire transmission might already be shot.

Frequently Asked Questions (FAQs)

front end of car shakes when accelerating

Is It Safe to Drive a Car When It Is Shaking?

If it is just a slight vibration, you may continue driving and easing on the gas a bit. If you cannot afford to have your car looked at, it may still be safe to drive. Ensure that the shaking you noticed only happens when you go beyond a certain number of RPMs.

However, you should still commit to checking the problem as soon as possible. The reason is that this may worsen over time.

What Should You Do When Your Car Suddenly Starts Shaking While Driving?

Let’s say, for example, that you are driving on the highway and you feel your car starts shaking a lot. One thing you can do is immediately ease on the gas and turn on your hazard lights.

Pullover gradually to the shoulder and turn off the engine. Call a towing service immediately, especially if the shaking is quite strong.

Meanwhile, if you ease on the gas and the shaking stops, move your car onto the slow lane. Take the next exit. Take this opportunity to drive to the nearest garage to have your car checked out.

In Closing – Car Shakes When Accelerating But Not When Coasting

Does your car shake when you step on the gas but stop or at least weaken when coasting? There could be a couple of reasons for it. The following are just some of these reasons:

  1. Faulty or Damaged Inner CV Joints
  2. Damaged Engine Mounts
  3. Unbalanced Tires
  4. Loose Tire Lug Nuts
  5. Bent Driveshaft
  6. Bent Axle
  7. Shattered Wheel Bearings
  8. Stuck Brake Caliper
  9. Damaged or Disconnected Vacuum Hose
  10. Worn-out or Just Dirty Sparkplugs
  11. Improper Wheel Alignment

If your car suddenly starts shaking while driving, do not risk getting into an accident. Just carefully pull over to the side of the road.

If the shaking disappears when easing on the gas, drive your car to the nearest mechanic’s garage. The goal is to have it checked to fix the issue immediately.

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