Why Lawn Mower Is Running Rough? Superb Guides To Fix Your Lawn Mower (2022)

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Lawn mower is running rough, but this does not mean that you have to give up on it.

There are several things that you can do to make sure that the mower runs smoothly,..

…and lasts a long time.

Check out Britanni’s story about her father’s lawn mower.

I just got accepted into a remote job, so I decided to stay for a while at my parents’ house.

Both of them like to be active.

My Mom is super into Yoga, while my Dad likes to take care of their lawn.

After a while, I started to notice that my Dad’s lawn mower runs…

a little rougher than how mine does.

I asked him if it was alright, but he brushed me off.

I got a little worried.

Is this something problematic, or should I just forget about it?

Read this article until the end to find out the answer to this issue.

In this blog, we also have an article about quietest lawn mower on amazon that…

…you might want to read about it.

A lawn mower is a machine utilizing one or more revolving blades to cut a grass surface to an even height.”


Why Your Lawn Mower is Running Rough

Lawn mower is running rough
Source: Getty Images

You know your mower best, especially if you use it on a weekly basis…

…during the busy mowing season.

You notice the engine isn’t performing optimally.

It starts out rough, sluggish, and bogging down.

Aside from engine damage, there are numerous causes for an engine to begin running rough.

When the air filter is clogged, water is in the fuel tank, old gas…

…causes fuel restrictions in the fuel filter, fuel lines, or carburetor,..

…the spark plug is bad, the gas cap is bad, and the mower deck is clogged,…

…the choke is set incorrectly, or the ground speed is too fast, and the lawn mower will run rough.

Follow the safety precautions outlined in your operator’s manual.

This includes stopping all moving parts and removing the spark plug wires,..

…so your mower does not start while you are working on it.

If your lawn mower had started smoking, read our guide about how to fix a smoking lawn mower.

In fact, the lawn is often the largest area of the garden. So having a high-quality lawnmower that suits your grass and garden size is vital. In fact, I think it’s the most important gardening tool you can own.


Water in the Gas Tank

Gas in your lawn mower or in a fuel can can start to degrade…

…and lose its combustible properties as soon as 30 days after purchase.

Most gasoline contains ethanol, an environmentally friendly alternative fuel added to gasoline.

Ethanol attracts moisture from the air by nature.

It will result in the formation of a gummy solution, causing restrictions in the fuel system.

Your lawn mower may run rough due to a loss of combustible properties and fuel restrictions.

Water in the fuel system can cause poor running performance,..

…and old fuel affects your mower.

This can occur if the mower is left outside in heavy rain.

I’ve even seen a young boy attempting to assist his parent by…

…inserting a garden hose into the fuel tank.

When water and gas enter the engine, it sputters because…

…water is not combustible and the engine has difficulty compressing it.

To fix this, use a siphon to drain your fuel tank.

Fill it with the appropriate fuel for your engine type.

If you can’t use the fuel within 30 days, stabilize it with…

…a product like Sea Foam Motor Treatment.

More information about Sea Foam and its effects on the fuel system can be found here.

Plugged Air Filter

Mowing isn’t the cleanest task regardless of the type of mower you use.

Mowers create a lot of dirt and debris.

When the engine doesn’t get enough air, dusty conditions can clog the air filter,..

…causing the lawn mower to run rough and sluggish.

Solution: Remove your air filter and inspect it.

Replace a dirty air filter when it is extremely dirty, covered in oil, or in poor condition.

Follow the instructions below to clean a paper air filter.

Clean a lawn mower’s paper air filter as follows:

  1. Remove the air filter housing’s air filter cover.
  2. Snaps, wing nuts, knobs, or clips secure the cover.
  3. Remove the air filter with care. Allow no dirt to enter the air intake.
  4. Remove any remaining dirt and debris from the air filter housing. Again, don’t allow any of it to fall into the air intake.
  5. Tap a solid surface with your paper air filter. Use the plastic or rubber edge to hit against the surface so you don’t damage the paper. You’re attempting to loosen the dirt so that it can fall out of the filter. (Using compressed air will damage a paper air filter.)
  6. Hold your air filter up to a light; if you can’t see light shining through the paper element or it’s covered in oil, don’t reuse it. Reuse the filter if it appears to be in good condition, and you can see light through it.
  7. Place the air filter inside the housing.
  8. Reassemble the air filter cover.

Damaged or Dirty Spark Plug

When the spark plug is dirty and covered with carbon buildup or oil,..

…the lawn mower may start running rough and have intermittent running problems.

When the tip of a spark plug becomes very dark in color,..

…the porcelain cracks, or the electrode burns, it must be replaced.

To avoid problems with your mower not starting or running,..

…make sure the spark plug gap is correct and the spark plug wire is securely attached.

Solution: Using a socket wrench, remove the spark plug…

…and replace it with a new spark plug.

Because a spark plug is required to keep your lawn mower running smoothly,..

…I prefer to replace it rather than clean it.

If you choose to clean a dirty plug, remove the buildup with a wire brush.

Plugged Fuel Filter

The fuel filter strains the fuel as it exits the tank to keep dirt…

…and other contaminants out of the fuel system.

When the fuel filter is not changed on a regular basis…

…or when the fuel is extremely dirty, the filter can prevent a fuel flow from passing through it.

When a higher concentration of air than fuel is burned…

…in the combustion chamber, a lack of fuel required for…

…the engine to run can cause it to run sluggishly.

Replace a dirty filter that is preventing fuel from flowing through it.

When installing the fuel filter, ensure the arrow on the filter points…

…in the direction of the fuel flow.

The arrow should point away from the fuel tank and toward the carburetor.

Fuel Line Restriction

Gummy deposits from old fuel can prevent a good fuel flow…

…from moving through the fuel lines.

As a result, your mower may run slowly or not at all.

For this, try to locate the clog in the fuel line and clear it.


Lawn mower is running rough 2
Source: Getty Images

The carburetor regulates the ratio of fuel and air mixed in the engine to form combustion.

The carburetor is located on the top or side of the engine block.

It is usually located beneath or behind your air filter.

When the carburetor becomes dirty due to deposits left behind…

…by old fuel, the fuel passageways can become clogged and…

…the engine’s small components can stick and fail to function properly.

This can prevent the proper mixture of fuel and air from…

…reaching the engine, causing it to run rough.

If you’ve confirmed that the bad spark plug and air filter…

…are in good condition and that you’re getting fuel to the carburetor,..

…the carburetor is most likely to blame for your sluggish running.

FIX: Remove the carburetor.

Most homeowners can do this if they are mechanically inclined…

…and don’t mind working with small parts.

Your local lawn mower repair shop can help if this isn’t you.

Fuel Gas Cap

To allow air to pass through a gas cap, it must be vented.

A broken or clogged gas cap will cause the fuel tank to form a vacuum,…

…preventing fuel from leaving the tank.

The mower will become sluggish and eventually shut down due to a lack of fuel flow.

If your mower is running slowly, remove the fuel cap…

…and let it run to see if the problem persists.

Take care not to let dirt or debris enter the fuel tank.

If the engine starts fine but then becomes sluggish and eventually dies…

…after you reinstall the cap, you may have a fuel cap venting issue.

Replace the fuel cap with a new one.

Types of lawn mower

Lawn mower is running rough 3
Source: Getty Images

Lawn mowers are divided into two types: Electric and Gas powered.

There are also several riding lawn mower types you can read in our blog.

Gas-powered lawn mowers are very popular in the US.

These lawn mowers have more power and also more features than electric lawn mowers.

But these gas powered lawn mowers have more maintenance costs…

…and also need to be refueled regularly.

Electric powered lawn mowers are less expensive than gas lawn mowers…

…but they cost more to run.

Electric-powered lawn mowers do not use fuel like gasoline and diesel oil.

They use electricity instead of fuel.

Some people prefer electric lawnmowers because of their low cost…

…and easy availability of electrical outlets everywhere and…

…also the environmental friendliness of them.

Electric lawn mowers are quiet compared with other kinds of lawn mowers.

In some cases there may be no sound at all except the…

…whirring blades of an electric lawn mower.

Electric-powered lawn mowing machines need a cord to start it up.

This cord provides electricity from a wall socket and also helps…

…you to push the lawn mower around

Sum Up

Knowing what to do to fix your rough-running lawn mower is easy.

If you’re unsure, it’s always better for you to call a professional.

Either way, if you feel like something’s wrong, get them checked out.


Do you have any experience with a rough-running lawn mower?

Do share your experience in the comment box!

Frequently Asked Questions Around Lawn Mowers Running Rough

Why is my lawn mower not running smoothly?

There are a few potential causes for an unruly lawn mower,..

…and the most common ones include clogged filters,..

…worn out blades or motors, and problems with the transmission.

Each of these can be corrected by performing a simple repair or Replacement.

If your Lawn Mower doesn’t start easily, check to see if it has gasoline in the tank.

If not, try pouring some Starter fluid into the carburetor to help it start (don’t overdo this!).

Cleaning all of the key parts of your machine such as blades and power cord,…

…regularly will also keep them running smoothly.

And lastly, make sure that you have adjusted its height settings…

….properly so that grass is cut at exactly the right level.

How do I stop my lawn mower from sputtering?

If your lawn mower is sputtering and not running at its full potential,..

…there may be a problem with the fuel filter.

This can become clogged over time due to residue build-up…

…from engine lubrication or leaves and other debris.

To fix this issue, you will need to remove the carburetor cover…

…and clean all of the parts that go into it.

Make sure to replace any damaged or old gaskets to give your lawn mower…

…fresh fuel injection every time you use it.

Why is my lawn mower chugging?

There are a few potential causes for your lawn mower to chug; the most common is misened fuel.

This can be caused by a number of factors, including dirty air filters,…

…clogged fuel injectors, or build-up of sediment in the carburetor.

In order to fix this issue, you will need to take some basic steps,..

…such as cleaning the engine and replacing any worn or disintegrated parts.

If these simple measures don’t resolve the issue, then it may be time for a new lawnmower.

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