Mower Engine Surging (Why + How to Fix)

If your lawn mower engine is surging, it can be frustrating and prevent you from mowing your lawn effectively. In this article, we'll discuss the common causes of mower engine surging and provide practical tips on how to fix them. By identifying and addressing the underlying issue, you can ensure your lawn mower runs smoothly and effectively.

Dealing with a surging lawn mower engine can be a challenging experience for anyone. Surging can cause the mower engine to rev up and down, leading to uneven cuts and an unsightly lawn. It can also make it difficult to control the mower's speed, making it harder to maneuver around obstacles. Additionally, a surging engine can indicate underlying issues with the mower's components, such as the air filter, fuel system, governor, throttle cable, carburetor, ignition system, or blades.

Table Of Contents

Understanding the Causes of Surging in Lawn Mowers

There is no single reason why a lawn mower surges, as a combination of factors can cause it. Identifying the underlying cause of the surging requires a diagnosis of the mower's specific symptoms and thoroughly inspecting of its components. It's best to check each potential cause individually to determine why the lawn mower is surging and take the appropriate steps to fix it. It can be caused by these factors, including:

Dirty air filter
Poor quality of fuel
Fuel problems include a clogged fuel filter, contaminated fuel, or a malfunctioning carburetor.
A dirty or worn spark plug
Speed governor issues
A loose or damaged throttle cable
Leaks in the intake manifold.
A malfunctioning ignition system.
Mower overload or dull blades.

By identifying the underlying cause of the surging, you can take the appropriate steps to fix it and ensure your mower runs smoothly.

How to Fix Your Mower Engine Surging?

Once you've identified the cause of surging in your lawn mower engine, we provide practical tips on fixing it to ensure it runs smoothly and efficiently. From cleaning or replacing air filters to inspecting and adjusting governors, we'll cover the steps you can take to fix your lawn mower engine and prevent surging in the future.

1. Air Filter

The air filter prevents dirt, debris, and other contaminants from entering the engine and interfering with its operation. This restricts the airflow to the carburetor, causing it to run lean or rich, which can result in surging. To fix a dirty or clogged air filter, you can start by removing the air filter cover and inspecting the air filter. If it is dirty or clogged, you can clean it by tapping it gently on a hard surface or blowing it out with compressed air. If the filter is too dirty or damaged, it may need to be replaced.

2. Quality of Gas

When fuel contains impurities, it can cause the carburetor to become clogged, resulting in surging. Poor quality fuel can also lead to water contamination, which can cause the engine to run erratically and surge. The fuel quality is impacted when it has been sitting for too long. Use high-quality fresh fuel with the correct octane rating for the lawn mower engine.

Additionally, fuel stabilizers can help keep fuel fresh and prevent the buildup of impurities, which can help avoid surging in the future. If you suspect poor quality fuel is causing surging in your lawn mower engine, it's best to drain the old fuel and replace it with fresh, high-quality fuel.

3. Fuel System

Several issues with the fuel system can lead to surging:

Clogged fuel filter: A clogged filter can restrict fuel flow to the carburetor, leading to a lean fuel mixture and surging.
Contaminated fuel: Contaminants such as dirt, debris, and water can get into the fuel system and clog the carburetor or injectors, causing surging.
Malfunctioning carburetor: A carburetor that is not functioning correctly, such as a stuck float, can lead to an incorrect fuel mixture and surging.
Old fuel: Fuel sitting in the mower for too long can break down and lose effectiveness, leading to surging.

To fix these issues, you may need to clean or replace the fuel filter, drain and replace the old fuel, or clean or rebuild the carburetor.

4. Spark Plug

A faulty spark plug makes an irregular spark that can cause surging. One way to test your spark plug is using an inline spark plug tester. If it turns out faulty, remove the spark plug and clean or replace it. You can also check the spark plug gap to ensure it is set to the manufacturer's specifications.

5. Governor

The governor controls the engine's speed. If the governor is not working correctly, it can cause surging. The governor spring can stretch out over time. You can simply adjust the spring or have it replaced if stretched out.

6. Throttle Cable

If the cable is damaged, it may not be able to provide a smooth and consistent supply of fuel, which can lead to surging. You may need to adjust the cable tension if loose by tightening or loosening the adjustment screw. A damaged cable may need to be replaced.

7. Vacuum Leaks

If there is a leak in the intake manifold or vacuum lines, unmetered air can enter the engine and cause it to run lean and potentially surge. To check for vacuum leaks, inspect the vacuum lines and intake manifold for any cracks, holes, or loose connections. If any leaks are found, they can be repaired by replacing or repairing the affected components. If left unresolved, vacuum leaks can cause other engine problems.

Final Thoughts

The frustration of dealing with a surging lawn mower engine highlights the importance of proper maintenance and regular inspections of the mower's components. Understanding the common causes of surging and how to fix them can save you time and money.

Routine maintenance, such as cleaning or replacing air filters, using high-quality fuel, and inspecting and adjusting components like the governor and throttle cable can help prevent surging and ensure a smooth, efficient mowing experience. If you fail to identify or fix the issue, you can seek the help of a professional mechanic to ensure your lawn mower runs smoothly and efficiently.