Can a Bad Alternator Cause a Misfire? (Yes or No)

Can a Bad Alternator Cause a Misfire

An alternator can last a long time but that is not to say it can’t go bad. If for whatever reason, an alternator goes bad you will most certainly know.

A bad alternator will show some obvious changes to the way an engine works but can it cause a misfire? Can a bad alternator cause a misfire?

Yes, a bad alternator can cause a drop in the electrical output of a car thereby causing a misfire.

What is Considered a Bad Alternator?

A bad alternator is one that is no longer able to charge a car’s battery while it is running. If the alternator is unable to recharge the battery, the battery drains out eventually.

The major work of an alternator in a car is to ensure that the battery is charged at all times, but due to some reasons, it may be unable to do so. In this case, the alternator is said to be bad.

What is a Misfire?

A misfire is when the cylinder doesn’t fire (remains unfired) due to the combustion reaction not working correctly.

A right combustion reaction is needed for an engine’s cylinder to fire, when this doesn’t happen, the cylinder will misfire or not fire at all.

When there’s a misfire, the engine will most likely experience reduced speed and stumble. This may occur once or multiple times at intervals.

Can a Bad Alternator Cause a Misfire?

Engine misfiring can be a result of various problems in the engine but can a misfiring be attributed to or caused by a bad alternator?

It is not really common but yes, a bad alternator can cause a misfire. For a bad alternator to cause a misfire it simply means it is not putting out enough power.

Parts of the car like the injector, spark plugs, etc., that work hand in hand to create combustion and ensure the cylinder fires correctly need enough power to work properly. When they are starved of it as a result of the alternator not providing enough power, the engine will most likely misfire.

The alternator cannot directly cause the engine to misfire but it can cause some parts like the spark plugs to malfunction leading to a misfire.

What to Do If a Bad Alternator Causes a Misfire?

If after troubleshooting the cause of the engine misfire you find out the alternator is the cause, there are a few things that should be done to rectify it.

The first thing to do if you are confused about what to do with your findings is to take the car to an auto shop. Mechanics at the auto shop will definitely know what to do to resolve the problem.

However, if you are confident about your abilities in fixing the problem. You should repair or replace the alternator.

The bad alternator is the root cause of the misfire here, therefore, you should repair or replace it depending on the severity of the problem. If the firing sequence is fixed without fixing the real problem, there will most likely be a reoccurrence.

It has been established that the alternator cannot directly cause the engine to misfire but does this through some of the firing sequences such as the spark plug, injector, etc.

In this case, you will have to change the spark plug. Without a functional spark plug, the various cylinders in the engine will misfire therefore, it is important to change and replace them when you notice there’s a misfire.

What are the Other Symptoms of a Bad Alternator?

Other than misfiring, there are other known symptoms of a bad alternator you should look out for. Some of them are;

1. Drained Out Battery

One common symptom of a bad alternator is a drained or dead battery. The car battery is charged by the alternator while running but when the alternator is bad there is no way to get the battery charged.

With no alternator to charge the battery, it will eventually run out of power.

2. Non-working Accessories

Other than charging the battery, the alternator is also responsible for powering accessories inside the car. In the event that the alternator is failing or completely bad, all of these accessories will not work as they should.

3. No Start or Stalling

If the engine is not starting when the key is turned in the ignition, then you are probably dealing with a bad alternator.

It could also be that the engine starts but stalls occasionally while driving. A bad alternator will cause power to drain out of the battery which is needed to start the engine.

4. Warning Light is on

This is a common symptom when there is a problem in the car. However. the warning light has been on doesn’t necessarily mean the alternator is bad it could be an indicator of other problems in the car

What Other Problems Can Cause a Misfire?

Some other problems that can cause a misfire are;

Worn Out Spark Plugs

Spark plugs are important for the proper firing of a cylinder, but it is possible that it gets worn out over time or were incorrectly installed.

If any of these happens, the spark plug will cause the engine to misfire. The incorrectly installed spark plug will cause air leakage and an air gap situation.

Problem with Emission Equipment

In the new model of cars, we now have equipment that helps to reduce the amount of pollution released. Although they are good, the downside to them is that if there is an issue with any of the equipment it will cause a change in the air/fuel ratio resulting in a misfire.

Sensor Problem

Modern cars have numerous sensors which are used to determine the control of some car functions. However, over time one or some of these sensors may have a problem that results in a misfire. This is a rare possibility but it is one that can’t be ruled out.

What Causes Alternator to go Bad?

The alternator can go bad for a lot of reasons, some of which are;

  • Wrong Usage of Jumper Cables: Jumper cables are good for when the battery is dead and needs to be revived, however when it is used wrongly it could damage the alternator and cause it to go bad. To avoid this, ensure the correct usage of the jumper cable
  • Leakage in the Alternator: For whatever reason, there may be fluid leakage inside the alternator, if it is not noticed in time and fixed it will eventually cause the alternator to become bad. Leakage will cause the internal parts of the alternator to rust and become useless.
  • Strain Due to Bad Battery: Not all alternators are designed to charge a fully discharged battery, therefore, constantly reviving a dead battery with an alternator will over time cause it to go bad. Too much strain and overworking an alternator will damage it.


If an engine misfires while driving, best believe it will most likely happen again, so rather than seeing how it goes get a mechanic to check it out and if you can do that yourself, that’s fine. The idea is to get the cause of the misfire fixed in time.