Can A Bad Alternator Cause Engine To Shake [Explained]

It’s a dreadful experience for any driver to see the vehicle’s engine shaking. If you’re facing this issue and you also have a bad alternator, you may suspect that the alternator could be causing the problem. So, can a bad alternator cause engine to shake?

Although it’s unlikely for a malfunctioning alternator to result in a shaking engine, it can happen in a few cases. A faulty alternator pulley, misfiring spark plugs, and a dead battery from a bad alternator can make the engine shake.

can a bad alternator cause engine to shake

Keep on reading this article to find out all about these problems in detail. We’ll also discuss the other more obvious reasons behind a shaking engine and car. Without further ado, let’s dive right in!

Note: You can also read our guide on can a bad alternator cause a misfire.

Can A Bad Alternator Cause Engine To Shake [Explained]

The alternator powers the electrical system in your car. Think of it as a charger for your vehicle’s battery. When you start the car, it’s the job of the battery to provide the initial burst of power required.

car bad alternator

Once you’re driving the car, the alternator gets activated and it charges the battery so that it doesn’t get depleted. So, you can understand why there’s very little chance of the alternator causing the engine to shake.

But never say never. There are a few instances in which an alternator can indeed cause the engine to shake. Some of the common scenarios when a faulty alternator can cause engine shaking are:

1. Misfiring Spark Plugs

The alternator supplies the power to the ignition coils and the spark plugs in many vehicles. When the alternator doesn’t have enough voltage, it may not be able to generate enough power for the spark plugs to fire at the right time.

misfiring car spark plugs

The spark plugs not getting power will lead to an engine misfire. And when that happens, don’t be surprised to see the engine shaking and vibrating. To know how to test a faulty alternator, keep on reading this article.

Once you can test whether you have a bad alternator or not, you can dive deeper into this issue. You’ll be able to figure out whether you need to replace another component or it’s actually the alternator that has gone bad.

2. Faulty Alternator Pulley

If you know how alternators work, you’d know that the alternator is connected to the drive belt. The part of the alternator that gets connected with the serpentine belt is called the alternator pulley.

faulty car alternator pulley

When the alternator pulley gets seized up, it can cause the serpentine belt to vibrate. The end result is that the entire engine will start vibrating and shaking.

Although the chances of this scenario playing out is unlikely, it can happen. You’ll have to replace the alternator if you face this issue.

3. Dead Battery

The alternator charges the battery when your vehicle is on the road. If you end up with a dead or depleted battery, your first instinct may be to believe that you have a bad battery.

car dead battery

Sometimes, you’ll have a faulty battery that has simply been used as long as possible. But it can also be an issue with the alternator. If the alternator fails to charge the battery when you’re driving your car, the battery will run out of charge sooner than you’d expect.

The battery won’t have the juice to start the engine in these situations. You can find the engine shaking and sputtering when it happens. Remember that a battery lasts for three to five years on average.

If you have a reasonably new battery, that’s a strong sign that you have a bad alternator. But don’t worry, you’ll learn how to diagnose a faulty alternator with certainty in the “How To Test An Alternator” section in this guide.

What Else Can Cause Engine To Shake

A faulty alternator is by no means a likely issue behind a shaking engine. There are many other issues that have much higher chances of causing the engine to shake.

You won’t have to scratch your head and figure out what these issues are. Here’s a list of the potential reasons behind a shaking engine and how you can fix them:

i. Broken Motor Mounts

The motor mounts are located between the body and the engine of your car. It does an important job of holding the engine and providing support to it. These mounts have a rubber center to absorb the shocks and vibrations that an engine faces when you’re on the road.

broken car motor mounts

When the motor mounts are damaged or broken, they won’t be able to provide the necessary support required by an engine. The movement of the engine can get even more prominent when you go over bumpy roads if you’re facing this issue.

Oftentimes, it’ll also be accompanied by a clunking noise from the engine. If the vibration or the shaking of the engine increases when you accelerate your vehicle compared to when you’re idling, there’s a strong chance that you have broken mounts in your engine.

So, the shaking of the engine decreasing when you put the car in neutral should tell you that you have damaged motor mounts. Unfortunately, the only solution to this problem is that you’ll have to replace the motor mounts. Doing that should get rid of the engine shaking issue.

ii. Clogged Fuel Injector

The fuel injector sends fuel to get mixed with the air and creates an optimum air-fuel ratio. When the fuel injectors get clogged and don’t supply the required fuel, the car runs lean.

clogged car fuel injector

The amount of fuel the fuel injectors need to send depends on the signal of the ECU of the car. So, clogged fuel injectors mess up the ratio of the air and fuel completely. The engine running lean can easily cause it to shake.

If you have clogged fuel injectors, the first thing you should do is try cleaning them. Getting carbon build-up out of them will be enough to solve the issue and fix the air-fuel ratio.

iii. Loose Or Worn Out Timing Belt

The timing belt needs to have the proper tension as its responsible for making many parts in your work. Fans and alternators won’t work properly if the timing belt is loose, overtightened, or worn out.

loose or worn out timing belt

To make matters worse, your engine may also shake and vibrate as a result of a bad timing belt. Inspect the timing belt and check if it’s loose. If it’s loose, you’ll have to tighten it and make it have the proper tension as mentioned in your vehicle’s owner manual.

If the timing belt seems to have the right tension, check it for visible signs of damage. You can use a flashlight to check whether the grooves of the belt are okay. If they’re damaged, you’ll have to replace the timing belt to keep the engine from shaking in the future.

iv. Worn-Out Spark Plugs

It’s common for worn-out spark plugs to cause the engine to shake. There used to be a time when spark plugs could last for 10,000 -12,000 miles on average. But since then, they’ve been developed to be much more powerful than before and can last up to 100,000 miles or more.

worn-out spark plugs of car

However, it doesn’t mean that they can last forever. They’re not insusceptible to wear and tear. When they get fouled, they would cause the engine to misfire and that can lead to a shaking engine.

If your spark plugs are not close to the end of their lifespan, they can simply be dirty. You can take them out, clean them, and put them back in. That might solve the issue.

But if that doesn’t work or you know that you have faulty spark plugs, you’ll have to replace them. It’s a good idea to replace all the spark plugs together at once if you have multiple spark plugs that are failing.

v. Damaged Catalytic Converter

Your vehicle’s exhaust system needs to be in great shape if you want it to perform well without any issues. The catalytic converter is one of the most important components of the exhaust system as it reduces the harmful emissions of a car.

damaged catalytic converter

It does so by filtering and burning the toxic byproducts present in the exhaust gases. The catalytic converter not only does a critical job of reducing harmful emissions, but it also increases the efficiency of the car as the car uses the unburnt fuel again for combustion.

When the catalytic converter gets blocked or damaged due to any reason, excessive pressure can build up in the exhaust system. The unburnt fuel will no longer be returned to the engine for the second time combustion.

It’ll decrease the fuel economy of the car. Along with poor performance, the excessive pressure due to the presence of such a high amount of gas can also cause the car to shake. If you have a clogged or dirty catalytic converter, you can solve this problem by cleaning it.

In fact, it’s common for catalytic converters to get dirty as they’re dealing with emissions and you’d have to clean them from time to time. But if the catalytic converter is damaged and cleaning won’t solve the issue, you’d have to replace it with a new one.

Unfortunately, replacing catalytic converters isn’t a cheap job and it’ll easily cost a few thousand dollars to replace it. You’d be able to save the labor charges if you can replace it on your own.

vi. Disconnected Hoses

There are many hoses in a car that carry important things like air, fuel, coolant, etc. The engine needs these things to do its job properly. When there’s a leak or any of the hoses get disconnected, the engine will be starved of these things and that can make it shake.

disconnected car hoses

Besides the engine shaking, you may also face other issues like car overheating, engine misfiring, or the engine completely losing power and shutting down. If you have this problem, you’ll have to attach the loose hoses again or replace the ones that are damaged.

vii. Cracked Radiator Fan

The radiator fan keeps the engine cool by letting cooling air pass through the radiator. Sometimes, the radiator fan gets cracked and causes the engine to vibrate or shake. You may notice the vibration increasing when you drive at higher speeds.

cracked radiator fan

As you try to accelerate, the cracked radiator fan can make the engine shake sideways. You can find out whether you have a damaged radiator fan with a quick visual inspection. You’ll have to replace it.

What Causes Car To Shake

There are plenty of other things that can go wrong in your car and cause it to shake. This shaking won’t be due to an engine surge but due to problems with other components of the car.

It’s not the same as a shaking engine. Here are the most common issues that can cause your to shake or vibrate and how you can fix them:

i). Unbalanced Tires

When the tires are not balanced well, your car will shake when driving at higher speeds. Inspect your car and check if there are any flat spots. If they’re not severely damaged, you can rebalance them. Otherwise, you’ll have to replace the worn-out tires.

unbalanced car tires

However, it’s not the only thing that can go wrong with tires. If they’re underinflated and don’t match the air pressure suggested in your owner’s manual, your car can also vibrate.

Besides, uneven tire wear or other tire defects can make them fall out of the right alignment and cause the car to vibrate. Your tires can also be worn-out with time and cause your car to shake. In that case, you’ll have to replace the tires altogether to solve this issue.

ii). Unbalanced Or Damaged Wheels

Even if your tires are able to survive the impact when you drive through a deep pothole or low curb without being damaged, the same may not be true for the wheels in your car. They can go out of balance and cause the car to shake.

unbalanced or damaged car wheels

It’s not easy to diagnose if the wheels have gone out of balance on your own. You’d require the help of a mechanic to diagnose it. Besides them going out of balance, the wheel bearings can also be damaged in such cases.

You’d have to replace the wheels if they’re unbalanced or damaged. The new wheels should be checked with a wheel balancing machine to make sure that they’re placed in the right alignment.

iii). Brake Issues

The brake rotors, calipers, and brake pads make up the brake system in your car. When the rotors undergo a lot of wear and tear, their thickness can vary. They can also get warped with time.

car brake issues

When that happens, the brake rotors cause the entire car to go out of balance and cause it to shake. The brake calipers can also get stuck to the rotors and that can also make the car shake.

You’d have to inspect the different components of your brake system and find out where the issue lies. Once you find the faulty part, replace it with a new one and that’ll keep your car from shaking in the future.

iv). Steering Issues

Problems with the steering of your can also cause the engine to shake or vibrate. If your steering acts normally when you drive on a straight road but shakes when you drive through a curve, it’s likely that you have an issue with your tie rod ends.

car steering issues

On the opposite end, if your car is okay when going through curves but starts acting up when you drive on a straight path, your ball joints are bad. Make sure there’s enough steering fluid in your car as a lack of it will also cause these issues.

If you’re sure that you have enough steering fluid, the next step is to replace the faulty component. You already know when you need to replace the tie rod ends and when to replace the ball joints.

v). Suspension Issues

If you notice the vibrations increasing when you accelerate your vehicle, it could be due to suspension issues in your car. As it’s closely connected to the steering, it’s logical to check the suspension next.

car suspension issues

Any of the suspension components getting worn out or damaged is the most common culprit in this case. Once you identify the faulty part, all you have to do is replace it and the car will stop shaking.

vi). Axle Issues

Unfortunately, axles are highly susceptible to getting bent. Especially, if you go through a pothole with your vehicle. A bent axle will make your car vibrate and shake when you accelerate the car.

car axle issues

The shaking will usually be more vigorous if you increase the speed of your car. The driveshaft can also get bent and cause the same issue. Check them one by one. Replace the faulty component once you find it.

vii). Damaged CV Joints

CV joints are located at the ends of the drive axles. They’re used to connect the transmission to the wheels. When dirt, filth, or debris gets into them, they can get damaged.

damaged car CV joints

Inadequate lubrication or excessive friction can also make the CV joints go bad. When that happens, the engine starts to shake more. The more the load on the car, the more it’ll shake.

You’ll have to replace the CV joints if they’re damaged. In some cases, the drive axles can also be damaged if you neglect the worn-out CV joints. You’ll have to replace the drive axles too in those instances.

How To Test An Alternator?

It’s important that you know how to diagnose a bad alternator. When you can conclude with certainty whether you have a bad alternator or not, you can take your next steps with clarity.

If the alternator is malfunctioning, you can replace it. Otherwise, you’ll have to diagnose the other potential issues behind the engine shaking and fix them. There are two common methods to test the alternator.

The first method is to check the alternator using a multimeter. The second one is to check it with an OBD reader. Let’s look at both of them.

Method 1 – Using A Multimeter

Place the multimeter leads on the positive and negative terminals of the battery and collect the readings. When the vehicle is not on, the voltage should be between 12 to 13 volts if you have a good battery.

using a multimeter to test an alternator of a car

Once you turn the vehicle on, the voltage reading should jump to 13 or 14.5 volts within a few seconds. If that doesn’t happen and the reading stays outside this range, you have a bad alternator.

Method 2 – Using An OBD Reader

The check engine light has to be turned on for you to test the alternator using an OBD reader. Connect it to the diagnostic port of your car and the error code – P0562 will pop up if you have a bad alternator.

using an OBD reader to test an alternator of a car

Make sure that the oxygen sensors and the ECU are fine if you check this code. Because errors with these components can also trigger this code even when the alternator is working properly.

Here, watching the video on how to test an alternator will be helpful for you.


Can a bad alternator turn on the check engine light?

A malfunctioning alternator can trigger the check engine light in a few cases. But it’s more common for it to illuminate the ALT or GEN light or the battery icon on your dashboard.

How fast will a bad alternator drain the car battery?

The rate at which the alternator will deplete the battery depends on how serious the issue is. It can range from a few hours to a few days depending on the condition of the alternator and the power consumption of the car.

Can a bad alternator affect the acceleration of a car?

A bad alternator will start by creating issues with the electrical system of your car. But soon enough, it’ll lead to poor performance and reduce the acceleration of your vehicle.

How to test a bad alternator vs a bad battery?

A bad battery won’t be able to start your car. But if the battery keeps draining when you run the car, it means that the alternator isn’t charging the battery and you have a bad alternator.

What sound does a bad alternator make?

It’s common to hear a grinding sound in your car when the alternator goes bad. It comes from a damaged bearing. But a faulty alternator can also make a whining sound when the voltage regulator goes bad.


Can a bad alternator cause engine to shake? Hopefully, you know all about it in this article. Remember to test your alternator first if you have a shaking engine to rule out other potential issues. You can replace the alternator and solve the issue if it has gone bad.

If the alternator is good, check the other components one by one and replace the faulty one. That’s all you have to do. Let us know what was causing your vehicle’s engine to shake and how you solved it by leaving a comment below.

“Read our comprehensive guide on can a bad alternator causes overheating“.

About John M

John contributed as a technical head at an automobile company just 2 years after his post-graduation in Automobile Engineering. He loves to lead a free life, so he left his job & started blogging. Now, he does research on every automotive problem, part & product and seeks a better solution & best products & shares his findings with his readers to help them as well as to minimize their struggle.

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