Lawn Mower Sputters and Dies: 8 Reasons With Solutions

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If you regularly use your mower and it is quite old now, there’s a high chance that you will face a situation where it starts making weird noises and gives up on you midway.

Now, this might be the first time your lawn mower has died, and it’s natural for you to be panicked about it. But it is a more common issue than you think. Even if you take good care of your mower and do regular maintenance, you still might experience something like that.

Don’t worry because there is a cheap and easy workaround that you can easily do yourself. So, let’s look at why your lawn mower sputters and how you can fix it.

About Lawn Mower’s Engine

About Lawn Mower’s Engine 

Before we start discussing the reasons for your inconvenience, let’s briefly look at how a lawnmower’s engine works so you can have a clearer picture when we discuss the issues later.

Depending on your model, your lawn mower’s engine can be four-stroke or two-stroke. But its basic principles remain the same as any other engine. The engine powers the cutting blades and generates the necessary force to cut grass.

Here’s a step-by-step explanation of how a lawn mower’s engine works.

  • The engine starts by drawing in air through an air filter.
  • A carburetor or fuel injector then blends the incoming air with fuel in the right proportions.
  • A piston then compresses the air-fuel mixture to increase its temperature and pressure.
  • Then, the spark plug provides the spark required for igniting the compressed air-fuel mixture.
  • Once the mixture is ignited, it rapidly burns, creating a high-pressure explosion that forces the piston down the cylinder, giving the engine power. This is called the combustion.
  • Finally, after combustion, the exhaust gases are released through an exhaust valve.

This process is repeated cyclically to keep the piston moving up and down and generate continuous mechanical energy required to power the blades.

If your engine starts to sputter, here are some key areas where the problems might have originated.

  • Fuel system
  • Air filter
  • Spark plug
  • Ignition system
  • Compression
  • Exhaust system

Check out the next section to understand how these parts can cause your mower’s engine to sputter and die, along with other possible reasons.

8 Reasons Why Lawn Mower Sputters and Dies and Ways to Fix Them

Here are some reasons your lawn mower’s engine might sputter and die. So, let’s find out which is the case for you and how we can fix it!

1. Clogged Air Filters

Clogged air filters

After knowing the mechanism of a mower’s engine, you already know how important the air is. But it can’t just pass any air to the fuel injector, so it needs to get purified first.

Every engine has an air filter, which constantly filters dust and debris from the air and passes it to the carburetor. While helping filter the air, the part itself gets dirty, and often, a dirty or clogged air filter is the most common reason behind engine sputtering.

How to fix it?

Depending on the type of filter, you can either replace it or clean it. If you have a paper air filter, you need to replace it. But for a foam air filter, you can clean it with some lukewarm water and dish soap.

After washing, remember to squeeze out the excess water and air-dry it completely.

2. Using Old/ Bad Fuel

We know gas prices are high, so you might feel tempted to use that old fuel that has been there in your garage since last summer, but think twice before you do that.

At first, your mower might work fine. But the impurities will soon catch onto the interior of your engine, making it all sticky and non-functional.

So, what are the ways to prevent this?

You must refrain from using old or bad fuel.

Also, you shouldn’t use low-quality gas that contains 10-15% ethanol. Ethanol burns way faster than pure gasoline, causing the plastic parts to melt. Those molten parts can be a reason your mower engine sputters and dies.

You should also never store your mower with fuel in its tank. If it sits in the mower’s engine for more than a couple of months, it can lead to sputtering. But if you must store the machine with fuel in its tank, add a fuel stabilizer to extend its shelf life.

3. Dirty Fuel Filter

Dirty fuel filter

Just like air filters, your fuel tank has a fuel filter that gets dirty over time. Clogged and dirty fuel filters will prevent the flow of gasoline in the engine. As a result, your engine will not get enough fuel and will start sputtering.

Pro Tip: The solution is to clean them from time to time or replace them if they are very dirty.

4. Clogged Carburetor

Apart from the filters, another part that gets easily clogged is the carburetor.

As the carburetor constantly mixes incoming air with fuel and is next to the combustion chamber, it gets coated with a sticky by-product of burning hydrocarbons.

This sticky layer not only affects the functioning of the carburetor but can also contaminate the good fuel in your fuel tank.

DIY tip: You can use a carburetor cleaning spray regularly to melt away the sticky buildup. We recommend spraying it every time you clean your air filter.

5. Faulty Gas Cap

Faulty gas cap

A gas cap is the part that prevents water from damaging the fuel system along with filtering dirt and debris.

If your gas cap is damaged, your fuel system becomes much more susceptible to external threats like moisture and dirt.

Besides, it also helps regulate the venting system. Meaning it regulates how much air should enter the gas chamber. If the cap is broken, air might not get in, and as a result, the entire fuel system will fall apart, and the engine will die.

It is an easy fix: Change the cap if you see it is damaged or bent and restricting the vent hole.

6. Moisture in Fuel Tank/ Line

If water gets in your mower’s tank, it will be a problem for your engine to ignite properly.

How do I find it out and Fix it?

Well, you can remove the gas cap and see if there are any traces of moisture.

If you see any signs of water, there is no other option for you than siphoning or draining the fuel tank and adding new gas.

7. Damaged Spark Plug

Damaged spark plug

Since spark plugs are tasked with ignition and heat dissipation, their central electrode undergoes gradual erosion due to the constant spark generation. On top of that, if there are things like carbon buildup or overheating, they might wear out even sooner.

So check if the plug is damaged or worn out and if it needs to be replaced.

DIY workaround:

If it’s not damaged but simply dirty, you can remove it, clean it with a toothbrush, and reinstall it. Remember to reset the mower into the manufacturer’s setting while reinstalling the spark plug.

Don’t remove the spark plug first since, in most cases, they are not the culprit behind a sputtering engine. However, you can clean or replace it if you see it is dirty or damaged.

8. Dirty Mower Deck

If you barely ever look under your mower’s deck, chances are that’s where the problem is.

Often, grass cuttings get caked on the mower’s deck, causing it to sputter. It is even more common if you cut wet grass or grass that grows tall. In that case, you will notice your mower sputtering as soon as you start cutting the grass.

How to fix it?

Jack your mower and check underneath it for piled-up grass. As a safety measure, you can take a wrench to remove the spark plug first to prevent the mower from turning on while cleaning it.

Once it is off, you can scrape off the excess grass using any scraping tool.


How long does a mower’s spark plug last?

A lawn mower’s spark plug usually lasts for a maximum of two years. While this is the maximum lifetime for a spark plug, changing it every 30 engine hours is recommended.

Is it safe to attempt DIY repairs on my sputtering lawn mower engine?

It depends. Based on the severity of the problem and your knowledge level, you should decide whether you can or can’t DIY the fixing. For example, most people can DIY the filter and deck cleaning, while some may not be able to get the spark plug out.

Can you clean a mower’s carburetor without removing it?

Yes, you can clean the dirt and buildup on the carburetor’s exterior without removing it. But if it is internally clogged and you need to clean it, you have no choice but to remove it.

Final Thoughts

I hope this guide helped you identify why your mower is sputtering and dying whenever you try to use it. If you are a first-time mower user, it is normal to get worried seeing your machine malfunctioning, especially when it is as expensive as a mower.

But don’t worry, sputtering is common if you last cleaned your machine some time ago. So keep cleaning it from time to time, and follow the tips we mentioned here to prevent it from malfunctioning again.

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