Can A Bad Alternator Cause A Misfire: Explained

There can be many reasons behind an engine not being able to fire one or more of its cylinders. And if you also see a faulty alternator at the same time, you may think that the alternator is causing the issue here. So, can a bad alternator cause a misfire?

It’s rare for a faulty alternator to lead to an engine misfire. That’s mainly because the alternator only powers the electrical components and isn’t directly related to the engine. With that said, there are some parts that require power from the alternator to start the engine.

can a bad alternator cause a misfire

Keep on reading this article to find out all about it in detail. You’ll also learn the main symptoms of an engine fire and how you can properly diagnose a bad alternator. Without further ado, let’s dive in!

Can A Bad Alternator Cause A Misfire [Know A-Z]

A faulty alternator isn’t the most common culprit behind an engine misfire. There are plenty of issues that are much more likely to cause a misfiring engine. More on that later.

car bad alternator

But that doesn’t mean that a faulty alternator can never cause an engine to misfire. In some instances, a misfiring engine can be the result of a bad alternator. Even though the result may not be direct at times, you can blame the alternator for this issue.

Note: You can also read our guide on can a bad Alternator cause overheating.

Scenario 1:- A Dead Or Depleted Battery

Whenever you’re facing an engine misfiring issue because of a faulty alternator, there is a high chance that you’ll end up with a dead or depleted battery. And that can cause an engine fire.

dead Or depleted battery

As you may be aware, the initial power that’s required to start a car is provided by the battery. If the battery doesn’t provide the necessary power to the engine, all the cylinders won’t get fired.

The alternator is responsible for charging the battery when you’re on the move. If it doesn’t do a good job of charging the battery, the battery won’t be able to provide the initial power required to start the car.

So, what happens here is a faulty alternator leads to a dead battery. When the battery is low on charge or out of it, it can’t provide enough power to the car. A faulty alternator leading to a dead battery ultimately leads to an engine misfire.

Scenario 2:- Not Firing The Spark Plugs

This is not a common issue and it only happens in rare cases. The spark plugs rely on the power from the alternator to fire the engine.

When the alternator fails to do its job and doesn’t provide the sufficient electrical current required by the spark plugs, the engine can sputter.

not firing the spark plugs

Keep in mind that the spark plugs need power from the alternator to ignite the mixture of air and fuel that was created in the combustion chamber. If they’re not firing, the spark plugs themselves can be bad.

Don’t jump to a conclusion unless you know for sure that you have a bad alternator and functional spark plugs. Only if both these things check out, then you should spend time inspecting this potential issue.

Scenario 3:- Intermittent Grounding Of The Alternator

Again, this issue is also not very common but you may face it at times. Keep in mind that we’re talking about an intermittent grounding issue here. If there was completely bad grounding in the first place, you’d already be facing a plethora of problems.

These issues include reduced charging, flashing or dim lights, or even complete loss of electrical power. You can test whether this is the issue by disconnecting the alternator in the middle of driving.

Before you do that, make sure that your battery has enough juice to run the electrical components for a few minutes. If the engine misfiring issue goes away when you disconnect the alternator, you can know for sure that the alternator is causing all the trouble.

What Causes Engine Misfire

It should be pretty clear by now that there’s very little likelihood that the alternator is causing an engine to misfire. So, naturally, you’d want to know what are the more common causes behind this issue.

Don’t worry, we won’t leave you high and dry. In this section, we’ll talk about the main reasons that cause an engine to misfire.

1. Old Or Dirty Spark Plugs

Having old or worn-out spark plugs is the number one reason behind an engine misfire. Spark plugs need to fire at the right time to produce a spark and ignite the air-fuel mixture. When that doesn’t happen, the engine misfiring issue is caused.

old or dirty spark plugs

At first, you can try taking the spark plugs out and cleaning them. If that doesn’t work, you’ll have to replace the faulty spark plugs. A single spark plug costs around $25 or more. If multiple spark plugs are failing, you can get the entire set replaced for $200- $400.

Thanks to modern technology – the lifespan of spark plugs which used to be around 12,000 miles has increased a lot. But that doesn’t mean that they’ll last forever. You can expect spark plugs to last for 100,000 miles these days.

Keep in mind that oil leaks getting into the spark plugs can make them go bad much more quickly. If you’re facing this issue with relatively newer spark plugs, it could be something worth checking out.

2. Clogged Fuel Injectors

The fuel injectors in your car’s engine supply fuel to the cylinders. Usually, one injector supplies fuel to a specific cylinder. When any of the fuel injectors fails to supply enough fuel to its designated cylinder, the ratio of the air-fuel mixture gets messed up. It leads to an engine misfire.

clogged fuel injectors

The fuel injectors usually get clogged with time due to plenty of fuel deposits. If one specific cylinder causes the misfire issue every time, it’s a sign of a clogged injector. First, try cleaning the injectors. But if that doesn’t work and if they’re damaged, you’ll have to replace them.

3. Dead Battery

The initial burst of power required to start the engine comes from the battery. An electric current goes through your car’s ignition system as well as the electric components through the battery when you start your car.

If your car battery is dead, it would lack the power required to start the engine. And that can easily lead to an engine misfire. If you have a dead battery, you’ll have to replace it.

4. Faulty Sensors

The two critical sensors that are required to fire the engine properly are the Mass Airflow Sensor and the Oxygen sensor. The MAF sensor takes note of the incoming air into the engine.

faulty MAF sensors

The ECU takes this information into account and sends the right amount of fuel required to achieve a healthy air-fuel ratio. The oxygen sensor also does the same job and detects the level of air. The only difference is that it monitors the amount of oxygen in the exhaust.

When any of these sensors fail to do their job properly, the correct mixture of air and fuel won’t be created. And that can cause an engine to misfire. Check both of these sensors and if any of them has gone bad, replace them as soon as you can.

5. Faulty Ignition Coil Pack

The ignition coil packs are an important part of the ignition system in a vehicle. Their main job is to collect a low level of current from the battery and increase it to start the engine.

faulty ignition coil pack

Think of them as a loudspeaker that increases the volume – but for the ignition system. When they go bad, the power of the battery isn’t enough to fire all the cylinders and that causes the engine to misfire. Replace the ignition coil in your car immediately if it has gone bad.

6. Leaky Head Gasket

The head gasket in your engine keeps the coolant and oil from being mixed with each other. When it gets blown for any reason, the engine oil and coolant get mixed, and that can even get into the cylinders. When it happens, it can cause an engine to misfire.

leaky head gasket

Usually, you’ll see multiple cylinders misfiring when the root problem is the head gasket. If you notice the same cylinders misfiring even after moving the spark plugs around, it points to a blown head gasket.

Head gaskets are notoriously expensive to replace and it takes an expert to do this job. So, get prepared for a hefty bill if you’re facing this issue.

7. Malfunctioning ECM

The ECM or the Electronic Control Module is the brain of the computer. It takes the readings from all the different sensors located in your car and makes the spark plugs fire at the right time.

malfunctioning ECM

But when the ECM goes bad, it can collect faulty readings and that can lead to the wrong action. With time, ECM can go bad and throw false codes. If that happens, you need to get it replaced.

How Can You Tell If Your Engine Is Misfiring

There are a few signs that you can be on the lookout for if you’re not sure whether you have a misfiring engine. Let’s look at them.

Loss Of Acceleration

Paying attention while you drive is the perfect way to figure out if you have a misfiring engine. You’ll experience a loss of power and have difficulty accelerating the vehicle when an engine misfires.

Keep in mind that you’ll be able to drive normally most of the time. The loss of acceleration can only be for a brief moment when you press the throttle.

Vibrating Engine

As the engine loses its power during a misfire, it tends to vibrate and shake excessively. Be on the lookout for this jerking motion of your car. Idling your vehicle can also be difficult when you come to a stop.

Weird Sounds

Hearing your vehicle struggling is a strong sign of a misfiring engine. You’ll often hear a popping or banging noise in the event of an engine misfire. It’ll only happen for a brief moment as the engine misfires.

You’ll be able to hear this sound even if you’re not an expert on automobiles. You can hear this sound from both inside and outside your vehicle. Sometimes, you may have to turn your radio and speakers off to hear the misfire.


Why does my engine misfire when accelerating?

The most common reason behind an engine misfiring during acceleration is worn-out spark plugs. Make sure you fix it ASAP. Otherwise, you can hurt yourself as well as others on the road.

What are the signs of a bad alternator?

The main symptom of a faulty alternator is flickering, overly dim, or bright lights. Along with that, a dead battery, illuminated battery light, loss of electrical power, and strange noises point to a bad alternator.

Why does my engine misfire only when idling?

A bad oxygen sensor is normally the main culprit behind an engine misfire when idling. However, clogged fuel injectors and vacuum leaks can also cause this issue. Hearing a hissing sound near the engine is a sign of a vacuum leak.

What damage can a misfire cause?

Continuing to drive your car with a misfiring engine can lead to catastrophic damage. Your catalytic converter and crankshaft bearings can get damaged early on because of it. The absolute worst-case scenario is that it’ll lead to total engine failure.

Can you drive your car with a bad alternator?

Technically, it’s possible to drive your car with a faulty alternator. But you won’t be able to get very far as you’ll be relying solely on battery power. Within 20-30 minutes, the battery’s charge would be over and your car will stop.


Can a bad alternator cause a misfire? Now, you know that there’s a chance of the alternator causing the engine to misfire even though it’s a rare possibility. Regardless, you should give it your all to diagnose the issue before jumping to a conclusion.

Inspect the other issues mentioned in this guide that are much more likely to cause an engine misfire. Once you do that, you’ll have clarity on what’s actually causing the issue. Comment below if you have any more questions about the relationship between engine misfires and alternators.

” Read our guide on why brand new alternator overheating and how to fix it“.

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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