Reasons Why Lawn Mower Sputters But Runs

Taking regular care of your lawnmower is an important part of keeping it running well. Your lawnmower will be in better shape and work better if you take care of it on a regular basis. Even if you keep your mower in good shape, it may still break down.

If your lawn mower sputters but runs, then it means there’s hope for significant improvement and you don’t need to worry much. The fix for this is usually cheap, easy, and something you can do yourself as part of your regular maintenance.

Lawn Mower Sputters But Runs
Lawn Mower

Engines for Lawnmowers

Your lawnmower’s engine works with a combination of the right amount of gas, air, and a spark for combustion. Your mower needs all of these things to keep from sputtering and giving up. Most of the time, you can fix the problems that cause your mower to sputter on your own.


Nevertheless, there are times when it’s better to hire a professional. Check a few things to find out why your mower is sputtering, and then decide if it’s something you can fix yourself or if you need to call in a pro.

Water in The Fuel Tank

If there is moisture in the gas tank or the fuel line, it could damage the engine. It will keep the fuel from igniting properly, which will make your lawnmower sputter. There may be water droplets in the engine tank of your mower because of condensation.

There may also be water droplets in the gasoline container before it gets to the mower. Therefore, you have to regularly open the top and check the tank to see if there is water in it. You can tell if there is water in liquids by seeing if they separate into two phases or have different colors.

Water in The Fuel Tank
Water in The Fuel Tank

Filters that are Dirty or Clogged

It is one of the most common problems that can make your lawnmower sputter. Mowers use air filters to take in air from their surroundings and mix it with gasoline in the engine.

Therefore, if the air filter is dirty or blocked, it will make it hard for air to get into the carburetor. Dirt can also build up in the parts between the carburetor and the fuel filter, stopping fuel from getting to the combustion chamber.

Spark-Plug Problems

If your lawnmower’s spark plug isn’t working right, it might be hard to start, run poorly, or even break down and die. To figure out what’s wrong, you have to look at two parts of the spark plug.


The first is a firing tip, which is a bend in a metal that makes a space between the metals and electrodes.

Here, the metal bends may have rusted or the electrode tips may have been rounded off, causing the mower to sputter. The other problem is that the porcelain case can break, which makes the lawnmower less effective.

A Dirty Mower Deck

If your lawn’s grass grows up into the mower deck, then that could be one reason why your lawnmower is sputtering. It often happens when the grass in your yard is thick and wet.

If you use a side-discharge mower, the caked grass blocks the hole where the grass comes out, which makes the grass bunch up instead of spreading out evenly.

If you have a bagger, it can hold a certain amount of grass, and if you put more grass in than it can hold, the extra grass will be spread across your lawn.

Lastly, caked grass makes it harder for your mower to cut the grass above the blades. Because of this, as space gets tighter, the cut gets worse. This caked or built-up grass makes it hard for your lawnmower to get rid of grass, which can cause it to sputter.

The Wrong Fuel Or Old Fuel

Most gas at gas stations has 10% ethanol in it. Since this fuel costs less than pure gasoline, many people who own lawnmowers are tempted to use it. However, this gasoline with ethanol in it is known to burn quickly and melt plastic parts as a result.

It could be what’s making your lawnmower sputter. But if you’ve had your mower for a long time, the gasoline in it might have gone bad, making it not work properly.

The Carburetor is Full of Gunk

If you have been using the same mower for a while, the carburetor may have gotten dirty and clogged up with gunk. Such things can make a lawnmower stutter and cause the engine to stop running after it has been started.

The carburetor mixes gas and air in a way that gives the engine more power while using less gas. When there is too much air in the mixture, the power of the engine goes down. If there isn’t enough air, on the other hand, the mower will use too much gas.

If the carburetor can’t find a good balance between the two, your mower may sputter and then stop working.

Gas Cap Problems

The mower’s gas cap might not be vented right sometimes. Because of this, so much air is getting into the gas tank that it causes a vapor lock. If that’s the case, it could be why your mower has been acting funny.

Gas Cap Problems

Related Post: Briggs and Stratton Gas Cap Problems: 5 Things to Fix

How to Fix a Lawn Mower that Sputters but Still Works

  • You can use a fuel stabilizer to make the gas last longer, but I think it’s better to use gas without ethanol. It will help your lawn mower start on the first pull and make a tiger-like roar.
  • A little bit of liquid dish soap and warm water can be used to clean foam air filters.
  • Replace your unclean fuel filters.
  • If the gas cap is broken, bent, or the vent hole is blocked, you should get a new one.
  • Using a carburetor cleaning spray on a regular basis will help remove dirt buildup and keep the holes and hoses on your lawn mower clean.
  • If there is water in your tank, you need to drain it or siphon it out before you add more gas.
  • Put in a new spark plug.
  • Use a scraping tool, like a paint scraper, to get rid of the extra grass.
  • Last but not least, if you think you can’t fix your mower’s problem, call a professional before it starts to sputter and finally stops working.

Final Words

It can be hard to figure out why your lawn mower sputters but runs. But in reality this is very easy to do it yourself. Find out the problem first. Only then can you fix it.  

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