Lawn Mower Surging | Top 5 Troubleshooting Guide 2021

Fact Checked By James A Weber | Post Updated On: September 21, 2021

A very common problem that the lawn mower users complain is the engine surging. Surging refers to the engine starting properly but stopping in the middle with a misfire or surge. In such situations, you must know what to do!

Let us know how you can confront lawn mower surging and get your lawn mower engine ready to work once again! Have a look!

Problems and Solution to Lawn Mower Surging

Air Filter

When you go through lawn mower surging, the very first thing that can be the reason for this problem is the air filter. At times, the air filter gets clogged and it causes lawn mower surging. Let us learn how to clean the clogged air filter to ensure fewer complications.

When the air filter is dirty, engine surging of the lawn mower is common. Paper or foam is used for constructing the filters. All you need is to remove the foam filter and clean it up! As there is coating oil on the foam filters, the carburetor can get dirty too.

On the other hand, paper filters work differently. This is the most common problem and the fix is easy! Let us learn how to clean the clogged air filter to ensure fewer complications.

  • First of all, you have to check the spark plug and disconnect it. This is a necessary step when it comes to the repairing process of such devices. The spark plug can cause accidents.
  • Once you are done with the spark plug disconnection, you have to take off the air filter. After taking off the air filter, you have to get your hands on the housing of the air filter. Remove the housing too.
  • Now, it is time for you to clean the filter. For cleaning the foam filter, use soapy water. Wait for it to dry properly. Get engine oil coating and apply it lightly on the surface. In case of the paper filters, you must replace the filter here. Now, clean the filter housing and install the filter once again!

Fuel System

As there will be dust and pollution, the fuel tank cap hole might be clogged too. In that case, you will face surging. Here is a way to help you out!

The cap of the gas tank of your lawn mower has a small hole added to it. The work of the vent is to let the air get inside the tank. Also, it helps is adding back-pressure so that it is easy to deliver fuel to the carburetor. On the other hand, the hole is a little small.

So, it is easy for it to get clogged with a lot of dust and dirt from the mowing work. All you need is to clean the vent! In some cases, water gets inside the fuel and result in surging! If you keep the mower outside in too much rain, this can happen easily. Here is a way to help you out!

  • Firstly, you have to check the vent of your gas tank cap. Clean it up carefully. In most cases, it is dirty, so cleaning is a must.
  • After this, you have to get your hands on the gas tank and drain it. Then, check the gas bowl and clean it. A fresh batch of fuel can add more to the process. In some cases, fuel cleaners work amazing too.
  • Your lawn mower will be ready to use now! There will be no surging at all!


If you count on the most common reasons of your lawn mower surging, most of the people will complain about the carburetor. Yes, if the carburetor is dirty, you might see the surging anytime. If there is dirt, the flow of fuel will not be adequate and this will cause surging. Let’s learn how to deal with it.

It is always better to take the help of a professional when it comes to such engine issues. They will remove the carburetor and will clean it for solving the surging issues.

  • But you might want to do it at home. In that case, you have to disassemble the carburetor first by disconnecting the air filter and fuel tank. Also, get your hands on the breather pipe, governor control link and disconnect them. Disconnect the keeper ring along with the manifold too.
  • Once you are done disconnecting the carburetor, you have to take some carburetor cleaner and start cleaning it. Replace it if necessary.
  • Reassemble the stuff you have disconnected before and get the carburetor in work once again. There will be no surging at all!

Bad Spark Plug

The engine will not run properly if a suitable spark not delivered from the lawn mower spark plug. So be careful about the spark plug good or bad. The following 4 steps will help you out to repair a bad spark plug.

All you need is to check for them and replace the plugs if necessary! The following 4 steps will help you out to repair a bad spark plug.

  • To repair bad lawn mower spark plug, you should disconnect the plug wire
  • Remove the spark plug very carefully. For any worn-out electrode or cracks inspect the plug
  • Finally, Replace the spark plug with a new spark plug- use proper size which recommended by producer or manufacturer.

Leaked Vacuum


Another reason behind the engine of the lawn mower starting fine but stopping at the middle is vacuum leaks. Yes, it can lead your mower to stop and at times, you might end seeing misfires too!

At times, the carburetor of your mower is not tight. As a result, the loose carburetor will start sucking the air. It will take in air through the crevices.

Eventually, there will be air between the engine block and the carburetor. So, if there is a lot more air than it needs, surely, there will be a misbalance of air and gas. And as a matter of fact, the unbalance of air will affect the ratio of air and gas.

So, all you have to do is make sure that the ratio doesn’t get bothered! Let us check how we can solve it!


  1. Your first work in this case is to go through the carburetor. The bolts of the carburetor should be checked first.
  2. You must check the air intake manifold here. All you need is to tighten them.
  3. As they are loose and it is affecting your mower, you have to move forward and tighten them. Get the perfect fit and make sure it is tight.

Fuel Condition


Yes, you have dealt with the fuel system and the carburetor but the condition of the fuel is also a factor here. No matter how much clean the fuel tank cap is and how perfect the carburetor is working, if the fuel is not clean, you can never save your lawn mower from surging!

If you use old gasoline, it can cause severe surging and backfire. Also, contaminated gasoline can be the reason here! The gasoline gets contaminated by the water condensation at times. If you keep the gas inside the mower throughout the winter, it can get old or contaminated. So, let us learn how to solve the issue without facing any surging!


Firstly, you have to ensure that there is no old gas inside the tank. Mostly, the old gas is the reason for this and so, you have to take out the old gas first.

Once the old and contaminated gas is taken out, you have to get your hands on a siphon. All you need to do is save spills on your lawn mower engine along with the floor.

Now, check the manufacturer's guidelines. There is a specific ratio of the mixture mentioned there. Check it out and note it down.

Then, start adding some fuel stabilizers. Add it to the gas tank according to the noted ratio.

Now that you have added the stabilizer to the tank, you must add some gas. Make sure you have added a full tank of gas in this situation.

Now that the tank is ready, check if it is working properly or not. Start the engine of your lawn mower. Two to three minutes of the run will be enough to learn if the engine is working properly or not. This will help in circulating the fresh air.

Now, you have to check if you are facing any engine surging issues or not! And you are done!

Note: Mostly, the problems with the mower surging will get solved without any complication after running all these steps. However, at times, they might not be solved easily with this one.

In that case, your mower has serious internal problems that require professional hands to get them perfect. Make sure you that it to an expert and then work on the solution.

Reasons For Lawn Mower Surging

There are tons of reasons behind the lawn mower surging and backfires. However, here are some common causes of the backfire. Let us learn why our lawn mower gets into the fire!

In cases, if you tend to lower the speed of your lawn mower’s engine too fast, there is a chance of backfire or surging.

At times, gasoline is the only reason for backfire or surging. You must understand that it is a blend of alcohol. And the amount of blends of alcohol is higher here. As a result, it can cause a surge. Try to avoid using any sort of old oil. Contaminated oil is the basic reason for surging. So, new and fresh oil is necessary for this one.

The muffler construction is something you have to keep in mind if you are a lawn mower owner. The muffler construction can be the reason behind your mower starting and stopping with backfire.

There are several carburetors available in the market and some of them are prone to induce backfire. The internal transitional passage in some cases is more sensitive in some carburetors than the others. As a result, these can cause your mower to stop after starting!

The normal engine temperature might exceed in some situations. This can result in a backfire after you start the engine of your mower.

The carburetor adjustment in some situations is not done properly. As a result, it stays in a sloping position or it leans. If it is set too lean, it will end up in surging of your lawn mower.

FAQs on Lawn Mower Surging

What does engine surging mean?

If you think that engine surging refers to trouble-to-start engine or the engine that doesn’t start, you are probably wrong. Engine surging is much more than that. Knocking engine is not what engine surging refers to. When you are going through engine surging process, the engine will surely start and will also accelerate smoothly. But after some time, the engine will surge in speed or it will misfire!

Does vacuum leak cause lawn mower surging?

Yes, in some cases, the vacuum lean can be an issue of lawn mower surging. At times, the carburetor is loose. As a result, it sucks the air that stays between the engine block and the carburetor. As there is additional air, the air and gas ratio will not be perfect. In short, it won’t be able to move air and fuel rightly. You will see mower surging and irregular mower engine!

What causes a lawn mower engine rev up and down?

If you have a lawn mower that is hunting or surging, there might be issues related to the airflow of the engine. Engine requires air to run itself properly. But if this air is blocked, the engine will slow down and at times it will surge. All you need to do is ensure there is no blockage and your engine will run smoothly.

Wrap Up

This is how you can stop the surging issue of your lawn mower. If you have a lawn mower and you work regularly, these are the things you have to face almost every day! So, it is better to be prepared even before so that you can fight the problems!

If you have any queries or suggestions, don’t forget to comment below! Also, share your experience about lawn mower surging with us!

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