How to fix Lawn Mower Sputtering

A lawnmower is supposed to make your lawn mowing work easier, but without proper maintenance of your mower, you’ll have a more difficult time maintaining your lawn. However, even with proper maintenance, there will be times when you’ll have problems like sputtering with your mower.

Lawnmower sputtering is a very common problem that is mostly caused by dirty air filters and an indication of poor mower maintenance. Dirt present in the system will interrupt the flow of fuel supply to the combustion chamber. Lawnmower sputtering is an easy and inexpensive fix that includes regular maintenance and proper cleaning and replacement of the air filters.

What causes a sputtering lawnmower?

Some common reasons can cause your lawnmower to sputter and how you can fix them.

  • Dirty or clogged air filters

Dirty air filters are a very common problem that causes mowers to sputter. If there’s dirt in your engine system, it will starve your engine of oxygen needed for combustion. The best fix is to clean with soap and warm water then air dry or replace the filters every year at least every year.

  • Dirty fuel filters

With time filters get dirty, and just like the air filters, fuel filters in your mower need to be cleaned or replaced. A clogged fuel filter will prevent the proper flow of gasoline into the engine which will cause your mower not to function properly because of a lack of enough fuel. There will be an imbalance of air and fuel in your engine causing your mower to sputter and run rough.

  • Old or wrong fuel

The gas you get at your local gas station contains 10% ethanol which works well for cars, but can cause problems for your lawnmower engine because it’s low quality.

Ethanol burns quickly which can melt plastic parts causing sputtering in your mower. The shelf life of ethanol-blended gas is only a few months and if you store it in your garage for a few months it will go bad and lead to a sputtering mower.

The best option is to use an ethanol-free gas that will burn cleaner and help your mower to start without problems.

  • Worn or damaged spark plug

If the spark plug is deteriorating, worn-out, or damaged, you should replace it, and if the tip is dirty or fouled with carbon, clean it with a wire brush.

Also, check the spark plug gap using a spark plug gap gauge to ensure the set gap distance is correct according to your lawnmower’s manual.

The wrong gap in your spark plug can easily become fouled with carbon from nor firing properly. You can easily replace the spark plug at least every year.

  • Carburetor issues

If your carburetor is just dirty, you can use a carburetor cleaning spray but there may be other issues causing sputtering.

If the carburetor doesn’t have the correct amount of fuel and air, it can cause it to run rough.

However, it’s tricky to clean and repair the carburetor without prior experience so you might need a professional to clean, repair, and replace it.

  • A dirty mower deck

A clogged deck with grass clippings can also cause your mower to sputter.

If you mow wet and tall grass, the grass clippings can be built up under the deck and prevent the blades from spinning properly which will put a strain on the engine.

To fix it first remove the spark plug to prevent your mower from starting when you’re working, then use a scraping tool to remove the excess grass.

  • Moisture in the tank

If there’s water in the fuel line or fuel tank, it will prevent the fuel from igniting properly.

Condensation or a loose gas cap can allow water to get into the fuel tank or it could have been present in the fuel container.

To fix it you just empty the tank and fill it with fresh fuel. Make sure you properly dispose of the emptied fuel from your mower.

How to Fix lawn mower sputtering



How to fix it

Smoke from your lawnmower

Overfilling or leaks in the oil chamber

Turn off the mower engine and let it cool. Tighten the loose cap

Failure to start

An empty gas tank or leaking, damaged mower battery, dirty air filters, dirty spark plug

Replace the gas tank if leaking and clean or replace the air filters and spark plug

Reduced mower speeds

Damaged drive belt or dislocation

Replace the drive belt


A buildup of grass blocking the exhaust

Remove all the dirt, debris, leaves, and grass

Bumpy ride barrier

Oil inadequacy

Check the oil levels frequently and change it more often

Unusual and excess vibration

Bent or damaged blades, faulty drive belt, loosely mounted bolts

Replace the faulty parts and the damaged or worn out belt and tighten the loose bolts

Stuck or too hard to pull the starter rope

The flywheel brake or lawnmower blades dragging on the ground or stuck grass clippings

Check the flywheel brakes and clean and remove the grass clipping


A lawnmower is a very important gardening tool in your home, so you must know how to fix it and include other common lawnmower problems in your lawnmower maintenance routine to ensure your mower runs smoothly when in use. This will not only save you time, but you also get to save on you would have used to pay a professional.


How do you clean a carburetor on a lawnmower without removing it?

Since you can’t spray your carburetor when the engine is off, you’ll need to start the engine and spray directly at the center of the carburetor while it’s running. Any clogged dirt in your carburetor will be easily removed.

Why are my lawnmower smoking and sputtering?

Black smoke from your lawnmower’s engine is caused by a rich mixture of fuel and air. When there’s less air air to complete combustion the fuel left in the combustion chamber turns to smoke.

Also Read

Do Brand New Lawn Mower Blades need to be Sharpened?

Best Lawn Mower Belts 

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