Lawn Mower Sputtering (Causes + Fixes)

A sputtering lawn mower can become a nuisance if not fixed. It can lead to longer mowing times, an uneven trim and other general annoyances. 

There are many different reasons why a lawn mower can begin to sputter. Sputtering can be a fairly common issue and can have a variety of fixes available. Some of the most common reasons for sputtering involve moisture or dirt getting into the system. Luckily, most solutions are fairly straightforward.  

As the solutions to a sputtering mower are fairly simple, they can often be carried out during annual maintenance . Knowing the signs and what to look out for when faced with this issue can help fix it. 

What is Sputtering?

Sputtering refers to the sound that a lawn mower makes which may denote damage or an issue within the engine. Sputtering can be described as a series of spitting sounds, made in quick succession. Sputtering is often a warning sign that there is some sort of maintenance issue that needs addressing within your lawn mower. It is rarely a signifier of major damage, but it can become a larger problem if left untreated for long periods of time. 

What Causes Lawn Mower Sputtering?

Lawn mower sputtering can be caused by several different factors, and is often the cause of something becoming trapped within the lawn mower. Most fixes are fairly easy, but diagnosing the cause of spluttering may be somewhat more difficult if you don’t know what to look for. 


Lawn mowers can be very finicky when it comes to gas. Whilst some people assume that any gas is suitable for lawn mower use, there are certain types, brands and compounds which aren’t ideal. For instance, gas that is high in alcohol is more likely to result in a lawn mower backfiring due to the likelihood of it igniting. 

The best type of gas for a lawn mower is one that is low in alcohol or alcohol free. If you are using one that contains alcohol, perhaps making the switch could solve your sputtering woes. 

If the type of gas you are using isn’t the problem, consider the age of the gas. If it has sat inside the lawn mower for an extended period of time, it might be time for a refill. 

a lawn mower sitting on uncut grass


Moisture with nowhere to escape may be a cause of sputtering, especially if you store your lawn mower outside, or if it is exposed to condensation. Lawn mowers can get wet to an extent before the moisture starts to cause problems to its internal workings.

One needs to be wary of moisture getting into the fuel tank or fuel lines of a lawn mower, as it can result in sputtering if not dried out. You can check if your fuel tank or lines are affected by water by checking inside during general maintenance and ensuring that the liquids are not separated or different colors. 

Air Filters

Your air filters play a large part in maintaining the health of your lawn mower. If these filters are blocked or dirty, it can lead to issues such as overheating or spluttering. If the air filters are dirty or blocked, the air flow to the carburetor will be affected, leading to spluttering. 

Spark Plug

Your spark plug can affect startup and your lawn mower’s runtime. This could be either because there is damage to the spark plug itself, or because it is dirty and simply needs cleaning. The effects caused by spark plug malfunction may be the cause of any sputtering your lawn mower experiences. 

The Deck

The lawn mower’s deck may have a tendency to become caked in debris and grass from previous cuttings. This can lead to sputtering, as it can decrease airflow, the intake and outtake of grass, and can decrease the quality of your lawn mower’s cut. Regardless of whether this is the direct cause of your lawn mower sputtering or not, it’s sometimes worth cleaning the deck during routine maintenance. 

The Carburetor

The carburetor is similar to the air filters in that it can cause sputtering if left clogged and dirty. This can lead to both sputtering and the lawn mower’s power dying if left untreated.

The carburetor can lead to issues without being dirty and clogged up. If it is working incorrectly by failing to maximize power and minimize fuel consumption, it can lead to an excess of air in the system which may lead to sputtering, backfiring and eventual lawn mower failure. If this is the case, it’s best to speak to a professional for advice instead of attempting to fix the issue on your own. 

Gas Cap

The gas cap is located on top of the gas container and ensures that the gas is sealed within. If this cap is faulty, or isn’t screwed on correctly, it can lead to excess air getting into the system and be the cause of spluttering. 

How to Fix Lawn Mower Sputtering

Knowing how to fix your lawn mower’s sputtering depends on what is causing the mower to sputter. Depending on the cause, the solution will be different. 

Fixing Moisture

If you have determined that your lawn mower is sputtering due to an increased presence of moisture in the fuel lines or tank, the best thing to do is to replace the contents of the tank. This simply includes draining the gas from the tank and replenishing the supply. 

Fixing Air Filters

There are a few options when it comes to fixing a lawn mower’s air filters. These include either cleaning them, or replacing them. This depends on the severity of the damage to them and the material that they are made of. For instance, paper air filters will need to be replaced, whilst foam ones can easily be cleaned using dish soap and air dried before reinsertion. 

Make sure that your air filters are dry before inserting them back into the lawn mower.

Fixing the Spark Plug 

There are two parts to a spark plug that should be considered when it comes to fixing it. The firing tip and the porcelain housing. 

If the firing tip is causing the issue, simply clean it out using a wire brush and reset the gap between the metals and electrodes by following the manufacturer’s specifications. 

If the issue lies in the porcelain housing, the spark plug should be replaced with a new one. This is a simple task to carry out, and some people opt to replace their spark plug every time they complete general maintenance on their lawn mowers to keep them running smoothly. Of course, that is entirely optional. 

Fixing the Deck

The lawn mower’s deck is easily cleaned, and just requires some time and patience to do it. It can be scrubbed down using a paint scraper in order to scrape away any excess grass that could be causing an issue. Make sure before doing this to remove the spark plug to prevent accidental startup and avoid any accidents.

Fixing the Carburetor

A dirty and clogged carburetor is an easy fix as it simply requires cleaning it out and making sure it is clean during routine maintenance. Sometimes it can simply be wiped out, but specific carburetor cleaners exist and can be sprayed inside to prevent build up of gunk. 

Fixing the Gas Cap

Possible one of the easiest fixes on this list, you can easily fix any issues with the gas cap by replacing it with a new gas cap which fits your lawn mower’s model. 

Final Thoughts

A sputtering lawn mower is often caused by a fixable blockage in the system, be it from grass or dirt. Knowing what to look for when diagnosing the issue can ensure that it is solved quickly and less invasively. It also helps to solve these issues earlier to prevent further damage to the lawn mower’s system. If you ever find your lawn mower sputtering, make sure to check over each component to try and find a cause before sending it in to be looked over by a professional, as the solution is often a quick and easy one. 

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