How To Troubleshoot a Lawn Mower Not Running at Full Power

Have you ever faced an issue such as your lawn mower not running at its peak potential? Unfortunately, it is a typical experience for many mower owners. Consequently, the owner of a lawn mower must be familiar with the problem-solving process.

As part of the troubleshooting process, you will need to clean the air filter; check out the fuel system; adjust your speed control cable; clean your carburetor; clean your spark plug; and clean your blades.

This article will explain why a lawn mower not running at full power. Also, the cost-free troubleshooting process for this particular issue. Continue reading the article till the very end.

What Causes Lawn Mower Not Running at Full Power?

How annoying is it when you want to mow, but your mower is moving at a snail’s pace? This issue could make it difficult, if not impossible, to accomplish your work on time!

You may be able to expedite the troubleshooting process by being aware of the root causes of this problem.

A clogged air filter, contaminated oil or gas, tainted oil or gas, a clogged fuel filter, a clogged carburetor, and a clogged spark plug are just few of the many causes that might contribute to a lawn mower’s sluggish performance.

7 Steps to Troubleshoot a Lawn Mower That Not Running at Full Power:

There is lots of troubleshooting available on the internet to level your mower deck. But several approaches for troubleshooting may not be practical.

As a result, I have enlisted a straightforward and cost-free solution to the problem, and the outcomes certainly meet your satisfaction.

Things you will need to troubleshoot lawn mower not running at full power

Check the list of essential tools and materials for troubleshooting a lawn mower that is not running at full power:

4-In-1 ScrewdriverCarb Cleaner
Adjustable WrenchCompressed Air
Needle Nose PliersRPM Gauge
Half Inch Socket 
Nut Driver 
Safety Gloves & Goggles 

Step 1- Check the Oil Level

The first thing you must check is the oil level. Both low and high oil levels are responsible for the lawn mower not operating at maximum power.

If your engine’s oil level is low, there will be insufficient lubrication to keep the engine’s internal components moving smoothly. In addition, increased friction may generate heat in the engine, resulting in a loss of power. 

In addition, excessive engine oil in the crankcase may cause your engine to smoke. This dense smoke cloud might clog your air filter. 

To solve the problem, adjust the engine oil level to the right level using the lines on the dipstick as a guide.

Step 2- Clean the Fuel Tank

Next, you must ensure that the engine is receiving adequate oil. Due to low fuel quality, dirt might build up in the fuel tank. It will cause a variety of issues, including power loss.

You may diagnose blocked fuel lines by stopping and restarting flow by using the fuel shut-off valve or crimping the fuel line while inspecting fuel line sections.  

Spray the fuel line with carburetor cleaner to remove the blockage. After this blast of compressed air will clear the line of obstruction. If required, these processes should be repeated.

If you cannot remove the blockage, replace the clogged fuel filter by installing a new filter.

Step 3- Replace the Bad or Old Oil/Gas

Following that, check the quality of your fuel. The engine also loses power due to the use of old or poor-quality fuel.

If you use old or bad oil or gas, your fuel filter will get clogged and sticky. Eventually, the clogged fuel filter will prevent fuel from reaching the engine, resulting in the lawn mower losing power.

To resolve the issue, the contaminated oil or gas must be drained from the fuel tank. Then, refuel it with new oil or gas so that it can run at full power. 

Step 4- Clean the Air Filter

An air filter ensures the proper volume of air is introduced into the engine for combustion to occur and also removes harmful debris such as dirt and dust from the engine.

If it gets clogged with dirt and dust, it can negatively impact its performance. In addition, air flow into the carburetor is reduced when this occurs, resulting in power loss or difficulty starting the engine when the engine is underpowered.

If the air filter is dirty, a thorough cleaning will likely be sufficient to resolve the issue. Use compressed air to blast dirt from the opposite side as the air flows. It would be more practical to replace it if it were really dirty.

Step 5- Clean the Carburetor

Managing the air-to-fuel ratio and ensuring the engine consumes the right amount of each is critical for internal combustion engines.

When the carburetor is clogged, the engine is unable to perform properly. Eventually, it will cause your lawn mower not to run at maximum power. 

To clean the carburetor, the following steps should be followed:

  • Turn the shut-off valve or clamp the fuel line.
  • Remove the throttle cable using a needle nose pliers.
  • Using a screwdriver, remove the air filter and wipe it off with a rag.
  • Remove the carburetor.
  • Clean the outside of the body using compressed air.
  • Remove the carburetor bowl and use carb cleaner and a wire brush to clean the nut on the carburetor.
  • Check the stem for clogged holes and rinse out to unclogged holes.
  • Then reassemble the carburetor.

Step 6- Clean the Spark Plug

A spark plug delivers an electric current to the combustion chamber in order to ignite the mixture of fuel and air. However, if this gets clogged by dirt, it will not be able to produce the current constantly, eventually resulting in a loss of power.

To clean the spark plug, the following steps should be followed:

  • Remove the spark plug.
  • Clogged in spark plugs should be identified.
  • The side of the spark plug that was in the engine cylinder (The Tip) needs to be cleaned.
  • Adjust the gap on the spark plug by measuring the small space between the end of the electrode and its grounding piece at the very tip of the spark plug and matches it with the manufacturer’s recommendation.
  • Reconnect the ignition cable and place the spark plug back into the engine.

Step 7- Properly Adjust the Speed Control Cable

An incorrectly adjusted speed control cable is one of the most frequent reasons of a lawn mower operating at low power.

To resolve the issue, you must first locate the speed control cable on your lawn mower. Then, adjust the speed control cable appropriately and measure the speed by RPM gauge. Finally, it would be best to recheck the speed several times to get the maximum rpm.

You may see this video.


Before using, maintaining, or troubleshooting your lawn mower, you should always read the lawn mower’s instructions manual. Before beginning the comprehensive inspection, turn off the engine and unplug all power sources.

Frequently Asked Questions

Does Mowing Tall Grass Impact a Lawn Mower’s Ability to Run at Full Power?

Yes, mowing tall grass will strain the engine, resulting in a poor cut and more engine stress. This stress might cause your lawn mower not to run at maximum power.

Is Battery Responsible for Power Loss of Your Lawn Mower?

Yes, it is. Due to the battery, battery-powered electric lawn mowers may not be able to run at maximum capacity. As the batteries deteriorate over time, it may become necessary to replace them.

What Could Be the Reason for a Lawn Mower not Running at Full Power?

Some other potential factors might cause lawn mower operating not at full power. It includes height of the mower deck, blade condition, mowing tall grass, etc.

Can High Ground Speed Cause Power Loss of Your Lawn Mower?

Yes. Your mower may gradually lose its speed if you mow your lawn at an excessively high pace.

Final Verdict

The steps I have outlined to troubleshoot a lawn mower not running at full power will be apparent to you after reading this article. Now you can quickly have your lawn mower working at full power.

Make sure that you check the engine oil in your lawn mower before you begin mowing the grass. It is also vital to perform routine maintenance to prevent such problems.

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