can bad alternator cause misfire

Can Bad Alternator Cause Misfire

Engine misfires are a frustrating issue. It impacts fuel efficiency and the overall driving experience. So, can bad alternator cause misfire?

Yes, a bad alternator can cause a misfire. But indirectly. That’s why it’s hard to catch.

When I faced a misfire in my engine, I blamed the alternator for it. The misfire and the alternator problem started on the same day. I did deep research to find out how my bad alternator caused the engine to misfire. In this article, I will explain how bad alternators cause misfires. Let’s dive into the topic: can bad alternator cause misfire?

Alternator Role in The Vehicle

Alternator of a car

First of all, we should understand the role of the alternator. Alternators do more tasks than we think they do. Here are they:

Role of AlternatorDetails
Power GenerationThe alternator converts mechanical energy from the engine’s rotation into electrical energy. This energy powers various electrical components in the vehicle.
Battery ChargingCharges the battery of the vehicle and maintains the battery health by preventing depletion.
Voltage RegulationRegulates the voltage output to maintain a consistent and appropriate level of electrical power to protect the sensitive electrical components.
Ignition System SupportSupply power to the spark plugs for proper combustion in the engine cylinders.
Engine PerformanceBy powering various electrical systems, the alternator indirectly contributes to the overall performance and smooth operation of the vehicle’s engine by powering all electrical systems.

You can reduce alternator issues through regular maintenance, and you can diagnose the alternator by doing a bench test.

What Is Engine Misfire?

When one or more cylinders in the engine fail to ignite the air-fuel mixture, we call it an engine misfire. Engine misfire results in incomplete or no combustion in that cylinder.

What Are the Symptoms of Engine Misfire?

You can experience the following when there is a misfire in your engine:

Rough Idling

There is uneven idling in the engine misfire situation. You can feel some vibrations and uneven sounds.

Reducing Power

Misfires reduce the power of the engine as some cylinders don’t generate power. You can experience reduced acceleration and difficulty climbing hills.

Increased Emission

The misfiring cylinder releases higher levels of unburned fuel into the exhaust system. This increases emissions. Moreover, this can be a reason for the check engine light and failing your emission test. So, remember to repair the misfire, especially before going to the emission test.

Poor Fuel Efficiency

A misfire directly affects the mileage of your vehicle as it disturbs the combustion.

Engine Hesitation

When you press the accelerator pedal, the engine may hesitate. Misfires can create a noticeable delay in power delivery.

What Are the Reasons for The Engine Misfire?

Several factors can contribute to engine misfires.

Ignition System Issues

Faulty spark plugs, ignition coils, or ignition timing problems reduce the spark needed for the combustion process.

Fuel Delivery Problems

Insufficient fuel pressure, clogged fuel injectors, or a malfunctioning fuel pump are the main culprits for fuel delivery problems. This leads to an uneven fuel supply to the combustion chamber.

Air Intake Issues

Malfunctioning mass airflow sensors and clogged air filters disrupt the fuel-air mixture.

Engine Mechanical Problems

A worn-out piston, damaged valves, and a leaking head gasket can badly affect the combustion process and lead to misfires.

Can Bad Alternator Cause Misfire?

Let’s move on to our topic: can bad alternator cause misfire?

Yes. A bad alternator can cause misfires. But not directly. In gasoline vehicles, the alternator supplies power to the spark plugs, causing them to ignite. As I mentioned above, if spark plugs malfunction, it causes a misfire.

How Bad Alternator Affect the Spark Plugs?

You know that bad alternators cause voltage irregularities. Voltage irregularities have a huge impact on the performance of the spark plugs. Here is how it affects the spark plugs.

Weak Spark

Spark plugs need a high voltage to ignite the fuel mixture in the engine combustion chamber. If the voltage is irregular or low, it results in a weak spark. A weak spark leads to incomplete combustion and misfires.

Inconsistent Firing

Spark plugs need a consistent and precise timing of electrical pulses to fire at the correct moment during the engine’s combustion cycle. Then, what happens if there is a voltage fluctuation due to a bad alternator? It interrupts the timing of the electrical pulses to the spark plugs. This causes misfires.

Can Bad Alternator Cause Misfire in Diesel Engines?

Chevy Silverado diesel truck

Above, we discussed gasoline engines. Then what about diesel vehicles? You know there are no spark plugs or ignition coils in diesel engines. They use the compression ignition process.

Also, in diesel engines, bad alternators can cause misfires. The alternator supplies power to the fuel pump. If the fuel pump malfunctions due to a bad alternator, it disturbs the combustion process and causes misfires. Fuel delivery malfunctions cause misfires in gasoline engines as well.


Can an alternator get wet?

The majority of alternators are somewhat water-resistant, although water damage is still a possibility. How will my alternator react if it gets wet from rain? Your alternator may be damaged by water if it gets inside your car’s hood. The alternator may become damaged if it is immersed in too much water.

Can a bad alternator cause your car to run hot?

A bad alternator cannot directly cause the engine to overheat. The alternator and many other components run on the same belt, called the serpentine belt. If the alternator malfunctions, it puts a strain on the serpentine belt. So the engine has to work harder to rotate the belt. Then the engine will overheat.

To prevent the car from running hot due to a bad alternator, the only solution is to fix the alternator problem. You cannot bypass the alternator like the AC compressor, as the alternator is a mandatory component of the engine’s function.

What gauge wire for alternator to battery?

There should be a minimum of 8-gauge wire for the 100 and 120 amps and a minimum of 6-gauge wire for the 140 amp. This advice is predicated on your battery being positioned in the engine compartment of your car with a 1.2-meter battery line. A thicker gauge of wire is required for batteries mounted in the boot.

Can a bad alternator cause sputtering?

Yes, a bad alternator can cause sputtering, as misfires happen due to a bad alternator.


Can bad alternator cause misfire? Yes, a bad alternator can cause a misfire. Other than the alternator, there are many reasons for engine misfires. It is important to diagnose and fix the underlying reason for the engine misfire. As I mentioned above, ignoring misfires leads to low fuel efficiency, rough idling, and vibrations in the vehicle.

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