How to Fix Lawn Mower Sputtering? – Identify the Causes

Maintaining a lawn before 1930, when the first rotary mower came onto the scene, must have been a chore. After 1930, the work of a lawn owner was made easier with the help of this machine.

The lawn mower, like all other machines, needs regular maintenance to work effectively. This is even more important for slightly more expensive garden equipment like the lawn mower. You don’t want to be changing your mower every fourth night, do you?

Regular maintenance of your lawn mower includes sharpening its bladescleaning its carburetor, and changing its oil, among several other things.

Sometimes, regular maintenance is not enough. You may still encounter problems when using your mower. Almost all lawn mower owners have encountered one common problem at one point, or the other is lawn mower sputtering.

As much as it is a common problem, it can easily be fixed if you know what you’re doing. That’s why I’ve come up with this article to show you some major causes of lawn sputtering and how to tackle this problem.

Before we jump right in, what exactly is lawnmower sputtering?

What is Lawn Mower Sputtering?

Sputtering, in general, indicates an underlying problem that needs immediate attention. This problem is most times incomplete combustion in the engine or a blocked fuel injector.

When it comes to lawn mowers, the sputtering sound usually indicates a small issue that needs to be tackled immediately to avoid the machine stalling.

How Does a Lawn Mower Engine Work?

The lawn mower engine has a simple working mechanism; think of it as a car engine, only way smaller. To work on any engine, you need to know the working mechanism.

How to Fix Lawn Mower Sputtering

I know this may sound like a daunting task. But you do not have to learn every tiny detail about the engine, and just the basic will do.

Suppose you’re operating an engine with a manual starter, where you have to pull a rope a couple of times before it starts. The rope spins the engine causing it to force air and fuel to the engine through the carburetor. The carburetor ensures the right amount of air and fuel goes in.

The flywheel provides electricity to the spark plug. This spark plug ignites the fuel and air mixture. The ignition of the fuel and air causes a controlled explosion that drives the piston down and rotates the crankshaft.

Lawn Mower Sputtering: Causes and How to Fix Them

There are several reasons why your lawn mower might sputter. Understanding the root cause will make fixing it easy and straightforward. You’ll also be able to figure out if this is a DIY task or you’ll need the help of professionals.

With that being said, here are the causes and solutions.

1. Dirty Air Filters

dry air filter lawnmower sputtering

  • Cause: the air filter’s work is to clean the air going into the carburetor, after working for some time; this filter will get clogged by dirt. It is no surprise why dirty air filters are one of the major causes of a sputtering lawn mower engine. The dirt clogging the air filter will lead to a reduced flow of fuel to the combustion chamber.
  • Solution: replace the filter if it is a paper filter or wash and clean it if it is a foam filter. Use liquid soap and warm water to wash the foam filter, squeeze and dry.

2. Moisture in the Fuel Tank

  • Cause: remember the working mechanism? How ignition forces the piston down and rotates the crankshaft? Well, water in the fuel tanks makes ignition difficult. You may be wondering how water can get into the fuel tank. Moisture from the environment can be absorbed into the tank if it is not closed properly or if the tank cap is bad.
  • Solution: open the fuel cap and observe the fuel. If you notice moisture, tip the mower over to remove the fuel and replace the fuel. Tightly close the cap.

3. Old or Wrong Fuel

  • Cause: old fuel is less likely to burn properly than a new fuel. Wrong fuel can easily damage your mower engine. Wondering how you can get the wrong fuel? The fuel obtained from gas stations is usually okay for cars. Still, it may not do well in mowers because they often contain over 10% ethanol. This is because ethanol burns hot and can melt plastic parts.
  • Solution: avoid using fuel with more than 10% ethanol. Avoid using fuel with any ethanol if possible. Change the old fuel to a new one by tipping the machine and collecting the old fuel in a container.

4. Clogged Carburetor

fix lawn mower sputter

  • Cause: after using your mower for a while, gunky deposits start to form in the carburetor. Any time this deposit breaks off, it floats around in the carburetor and sputters the mower. It can even cause the engine to die after starting it when these deposits become too much.
  • Solution: clean the carburetor regularly. You can do this by spraying the cleaner directly into the carburetor’s intake. This will loosen the deposit that has been formed.

5. Bad Carburetor

  • Cause: I know I said you can clean your carburetor using carburetor cleaners to stop your mower from sputtering. This is only effective if the carburetor is only dirty. Sometimes the carburetor is simply bad. A bad carburetor will affect the amount of air and fuel entering the engine.
  • Solution: a bad carburetor needs repair or outright changing. Fixing a carburetor may be out of the scope of an average lawn owner except, of course, you have prior knowledge of carburetor repair. You may need to employ the help of professionals.

6. Dirty or Damaged Spark Plug

  • Cause: a dirty or bad spark plug can make your lawn mower difficult to start; it can also cause the sputter engine. Although a dirty or damaged spark plug is not a major cause of a sputtering engine, it may just be the cause of your mower sputtering.
  • Solution: remove the spark plug and clean the tip using a brush. Replace the plug regularly.

7. Clogged Mower Deck

Clogged Mower Deck

  • Cause: using your mower deck to cut wet grass will cause the grass clippings to stick under the mower deck. When this happens continuously for a while, the grass under the deck forms a cake and clogs up the deck causing the mower to sputter.
  • Solution: tip the mower to allow you access to the mower deck. But before that, ensure you remove the spark plug to avoid the mower accidentally coming on and causing damage. Use a scraping tool to remove the grass cake underneath.


Lawnmower sputtering may be a common problem associated with lawn mowers. Still, as you have already seen, Lawnmower Sputter can be handled quickly and easily. 

Whenever your mower begins to sputter, quickly go through these 7 causes and solutions to settle the issue.

About Jennifer Igra

Growing up in Brooklyn, New York City known for it’s green gardens. Jennifer, a 30 year old gardener and green living fanatic started Igra World to share her gardening journey and increase gardening awareness among masses. Follow Igra World to improve your gardening skills.

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