November 17, 2022
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Sputtering Lawn Mower ? Check THESE 3 Things FIRST!

Is your Lawn Mower Sputtering? Don't worry, you're not the first person to have that issue.

Picture this: you're all set to mow your lawn on a beautiful sunny day, but your lawn mower is making strange sputtering sounds and refusing to cooperate. 

What do you do?

Well, you've come to the right place. In this article, we'll cover three common causes of lawn mower sputtering and provide you with easy-to-follow troubleshooting steps.

Plus, we'll discuss common mistakes, best practices, and expert tips to help you keep your lawn mower in tip-top shape!

The lawn mower typically takes more abuse than almost any other outdoor tool, so this is no surprise AND I'm pretty sure I can help you fix it on own!

Running year after a year through high grass and coarse weeds, hitting against the rocks, dirt mounds, doggy bones, and similar obstacles certainly take its toll on the well-being of your lawnmower. In addition to this beating, a lot of owners skip maintenance actions and improperly store their lawnmowers leaving them at the mercy of rain, humidity, or heat.

So, although some believe that they will awork and cut grass forever, every lawn mower eventually breaks down and you'll need to repair it or replace its parts.  This could be as simple as your lawn mower sputtering, or worse...

Some lawnmower malfunctions require professional help and expertise but, luckily, you can take care of plenty of problems by yourself.

Lawn mowers are not overly complicated machines and their small engines feature a limited number of parts. Their operation principle is fairly simple and more often than not you'll be able to use your average homeowner's technical skills to diagnose and rectify the problem.

One of the most common issues lawnmower users face is that their engine starts to make funny sounds while making rounds around the lawn.

The engine running rough and "coughing" can sometimes be a symptom of a more serious underlying engine malfunction, but, usually, it's an easily solvable matter that you can handle without any extra help.

Here's something you DON'T want to hear about the sputtering in your lawn mower:

Mower Sputtering is mostly just the indicator of improper lawnmower maintenance and can be easily avoided by following the instructions and performing regular checks.

To run smoothly, the lawnmower engine needs:

  1. Fresh fuel
  2. A flow of clean air (so keep a look out for dirty air filters)
  3. And the ignition spark.

So, if your lawn mower sputters, the culprit can usually be found within these three processes.

Sputtering Lawn Mower? Here's 3 Common (And Easy To Diagnose & Fix) Causes!

If you let your guard down and allow dirt or bad fluids into the system, your lawnmowers engine will not only sputter but in time it may fail to even start or eventually die completely.

At that point, you'll have to turn to experts, or pony up the cash for the new engine for your mower.

When trying to figure out the cause of your lawn mower sputtering, you should start with the simplest and most obvious ones.

If you make sure that everything is in order there, but your mower engine still struggles, move on to the next step until you have exhausted all of the options within your expertise level. Below, we listed all of those steps related to the most probable issues causing the lawnmower to start sputtering.

1.) Check the Fuel System

Sputtering Lawn Mower

One of the most common reasons for the faulty engine operation in your mower is the bad batch of fuel inside of your lawnmowers tank.  This is good news since it's also the easiest issue to solve.

Here's a little Lawn Mower 101: Fuel is essential for the internal combustion process that powers your mower's engine. 

But, not all fuel is created equal!

For the best performance, always use fresh, high-quality gasoline with an octane rating of 87 or higher. 

Pro tip: Avoid using gasoline with more than 10% ethanol content, as it can damage the engine over time.

Try to remember when the last time was you filled the gas tank. If it was more than thirty days ago or even at the end of the previous mowing season, then the old gas is the probable suspect for your troubles. Here's Why:

  • Organic components within gasoline can quickly evaporate, making the old gasoline burn faster and rendering it useless. Your mower's engine probably has only one cylinder making it more sensitive to these issues than the ones found in cars with four or six cylinders.
  • The speed at which gas goes stale has a lot to do with the ethanol percentage it contains.

Always look to buy gas with less than 10 percent of ethanol, or, in the best case, completely ethanol-free.

  • Ethanol burns so hot that it can even damage some of the plastic parts. It also helps create water residue within the reservoir and that is definitely not good for the engine.
  • Water in the tanks can also come from condensation, or faulty and loose gas cap, especially if the mower isn't properly stored and protected from rain and humidity. If the water enters the cylinder it hinders its functioning due to a vapor lock.
  • If you determine that you have faulty gasoline in your tank, drain it and dispose of it responsibly.
  • Before you pour in the fresh batch of gas, shmoake your tank a little. Sometimes, an outside object can make its way to the tank and restrict the fuel flow by clogging the exit hose.

If the mower engine experiences gas flow stoppages, it will struggle and sputter. Another issue that can influence the proper gas flow is clogged fuel filter, fuel line, or air filters. Remember to check it and replace it if needed.

Besides the one on the mower tank exit, the fuel system contains at least one more filter (fuel filter or air filters) and a network of hoses and openings.

If any of them is clogged, the supply of fuel for the combustion chamber will not function in a way needed for the engine to run steadily.

So, make sure to also check the lines connecting tank, carburetor, and cylinder, as well as the fuel pump which is usually mounted on the carburetor. If they are dirty, try to clean them or, if that doesn't work, replace them.

2.) Inspect the Ignition

Lawn Mower Sputtering can often indicate issues with ignition. And these issues can usually be traced back to the spark plug.

A common misconception is that if the mower starts, the spark plug must be fine. However, a damaged or loose spark plug can lead to engine problems and poor performance.

According to James Duffy, a certified lawn mower mechanic from Cleveland, Ohio, "A faulty spark plug is one of the most common causes of engine sputtering. Regular inspection and timely replacement are crucial to avoid long-term engine damage."

A damaged or loose spark plug is often associated with starting problems, but it can also cause the engine to struggle and run poorly. If it's dirty or corroded with residue, the plug can no longer properly spark the fuel and set the engine operation in motion.

Here's What You Should Do:

1.) Remove the spark plug using the spark plug wrench and check the firing tip to see if it's clean. 

2.) You can clean oily buildup with an old rag or use a wire brush (or sandpaper) if it's fouled with carbon. If there is grass caked on the bottom, scrape it off using a paint scraper.  

3.) Use the spark plug gauge to measure the spark gap and see if it's set to the distance described in the instructions.

4.) The wrong gap setting will cause issues with the engine running and quickly create a carbon buildup.

If the ceramic housing is damaged, or the tip of the electrode is rounded over, you should replace it with a new one.
Lawn Mower Spark Plug
Since the mower spark plugs are rather cheap, it's a good idea to always have at least one spare lying around. When placing the spark plug back to the socket make sure not to overtighten.

If the spark plug issues persist, consider switching to a different brand. Besides emergency replacements, make installing a new spark plug a part of your yearly lawn mower maintenance.

By the way, you can get Spark Plugs and just about anything else you need on!

3.) Adjust or Clean the Carburetor

Once it receives the supplies of air and fuel from other components, the carburetor's job is to mix them properly to make the engine run. If the mixture is a bit off, the engine will sputter and struggle to maintain operating efficiency. Eventually, it may even die.

Although the carburetor usually performed poorly because it's clogged and dirty, it is possible that it just needs some adjustments:

  •  Adjusting the idle and low-speed setting on a carburetor is fairly simple. Each setting is controlled by a dedicated screw, usually clearly marked.
  • Opening these screws just a tiny bit increases the fuel flow to the carburetor and helps the engine run smoothly at these speeds (or at idle). 

Bear in mind, if the mower carburetor is dirty, this is just a quick and temporary fix.

The body of a carburetor contains jets, springs, floats, and needle valves, all of which are extremely minuscule and sensitive.

Sticky by-products of the combustion and fuel residue can create gunky buildup over these components preventing them from performing their function to the fullest.

If one of these gunky deposits breaks off, it can float through the system, clogging it and causing the whole engine to sputter. The sensitivity of carburetor parts is the reason why the tinkering with the carburetor is usually best left to the professionals.

Still, there's some cleaning you can try on your own to see if you can make your lawn mower sputtering stops.

Carburetor cleaner sprays can be bought at any better-equipped store and you can use it for regular preventive maintenance.

Spraying it directly into the intake helps dissolve the deposits and frees up the flow inside the carburetor.

Keep in mind that the process of adjusting or cleaning the carburetor may vary depending on the make and model of your lawn mower.

So, it's always a good idea to refer to your mower's user manual for specific instructions. If you're new to lawn mower maintenance and need a visual guide, check out this helpful YouTube tutorial that demonstrates how to clean and adjust a carburetor step by step.

Additionally, some modern mowers come with electronic fuel injection systems that eliminate the need for carburetors altogether, so be sure to adapt the maintenance process accordingly!

if you feel you're extra handy, you can try disassembling the carburetor and performing a thorough cleaning. 

Even getting to the carburetor is not a particularly easy task:

Depending on the mower engine type, you'll probably have to remove the fuel tank, air filters, breather pipe, fuel lines, and manifold seal. 

Carefully disassemble the carburetor and soak it in cleaning liquid.

You should leave it there overnight. In the morning carefully clean all of the components. You can use compressed air to blow through them, but be careful.

While you're at it, consider buying a carburetor repair kit and replacing all of the gaskets. Once you're done, reassemble it, put it on the back on the engine and reinstall all of the components on the mower in the reverse order.
Again, if you're unsure about any part of this process, don't even start with it and get the help of an expert. Another option is purchasing a new carburetor and replacing the old one.

What to Do if the Lawn Mower is Still Sputtering?

If none of the above methods work with your mower sputtering, consider your mowing practices.

Letting your grass grow too high before mowing or cutting it while still wet can also burden the engine and cause it to stutter.

See how your mower works when faced with less challenging assignments (shorter grass).

And if the problem persists, then there's no other option than taking your machine to a mechanic.

If the engine sputter is still present after you've performed all of the steps on our list, then probably have a serious engine issue on your hands.

Whether you try to take care of your mower yourself or leave it to a professional, the most important thing is to react as soon as you notice your lawn mower sputtering.

Continuing to work your mower in that condition can lead to irreversible damage and leave you with no other option other than buying a new one.

Final Thoughts

Sputtering is a common issue that lawn mower users may encounter, but with a little know-how, you can troubleshoot and resolve the problem in no time.

Remember to check the fuel system, inspect the ignition, and clean or adjust the carburetor if needed.

Be mindful of common mistakes and always follow best practices for lawn mower maintenance.

Your lawn mower is an investment, and with proper care, it'll serve you well for many years to come. Happy mowing!

Frequently Asked Questions

What are some common causes of a lawn mower sputtering?

Some common causes of a lawn mower sputtering include a clogged fuel filter, a faulty spark plug, or a dirty air filter.

How can I troubleshoot and fix a lawn mower that is sputtering?

To troubleshoot and fix a sputtering lawn mower, you can try the following steps: 1. Check the fuel filter to see if it is clogged or dirty. If it is, clean or replace it. 2. Check the spark plug to see if it is faulty. If it is, replace it. 3. Check the air filter to see if it is dirty. If it is, clean or replace it. 4. Check the carburetor to see if it is clogged or needs to be adjusted. If it is, clean or adjust it as needed.

Can I fix a sputtering lawn mower myself, or do I need to take it to a professional?

Some simple repairs, such as cleaning or replacing a fuel filter, spark plug, or air filter, can be done by a homeowner with basic mechanical skills. However, if you are unsure of how to fix the problem or are unable to diagnose the issue, it is best to take your lawn mower to a professional for repair.

How can I prevent my lawn mower from sputtering in the future?

To prevent your lawn mower from sputtering in the future, you can try the following steps: 1. Regularly check and clean or replace the fuel filter, spark plug, and air filter as needed. 2. Use fresh, clean fuel and add a fuel stabilizer to prevent the fuel from breaking down. 3. Store the lawn mower in a dry, protected area when not in use. 4. Follow the manufacturer's recommendations for maintenance and care.

What are some signs that my lawn mower may be about to start sputtering?

Some signs that your lawn mower may be about to start sputtering include a decrease in power or performance, difficulty starting, or unusual noises coming from the engine. Paying attention to these warning signs and taking care of any issues as soon as they arise can help prevent your lawn mower from sputtering.

Daniel Simmons

About the author brings my 25 years experience as a professional gardener and landscaper to you!

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