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14 Reasons Your Toro Mower Loses Power and Bogs Down

Your engine seems to be bogging down and not running strong. This is something that should be diagnosed and fixed right away not only for good performance but also to prevent potentially costly repairs.

A Toro lawn mower will lose power when the engine doesn’t get good airflow and fuel flow, or the engine runs hot.

This can be the result of a low engine oil level, clogged air passageways, plugged air filters, a dirty carburetor, or restricted fuel components.

A Toro mower may also begin to lose power when the engine is under load due to a plugged mower deck or too fast of a ground speed for the mowing conditions. Keep reading for more details.

Engine on a Toro mower

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Follow all safety instructions provided in your equipment operator’s manual before diagnosing, repairing, or operating. Consult a professional if you don’t have the skills, or knowledge or are not in the condition to perform the repair safely.

This is Why Your Toro Lawn Mower Loses Power & Bogs Down

1. Plugged Air Filter

One item that can cause your mower to lose power is the air filter. The air filter is essential to use to keep dirt from entering the air intake and damaging the engine.

However, you can also damage the engine if you don’t keep the filter clean. Because mowing is a dusty job with your mower kicking up grass clippings and dirt, the air filter can become plugged.

The buildup of dirt on the filter can keep air from passing through the filter causing the engine to begin to lose power and bog down.

It is good practice to replace your air filter with a new one annually. Then, clean it several times throughout the mowing season.

You may have to change and clean your filter more frequently if you are mowing in very dusty conditions.

How to Clean Your Toro Lawn Mower Air Filter
These instructions are for cleaning a paper-style air filter. Find instructions for cleaning other types of filters here.

  • Remove the cover from the air filter housing. This is often held on by clips, knobs, or wing nuts.
  • Carefully remove the air filter so you don’t allow dirt to fall into the air intake.
  • Clean out any dirt that remains in the air filter housing using a dry clean rag.
  • Tap your air filter against a hard surface to knock as much dirt loose and out of your filter as possible.
  • Hold your filter up to a light source. If you can see light shine through the paper, go ahead and reuse the filter. If you can’t or the filter is damaged or covered in oil, replace it with a new air filter.
  • Install the filter and reattach the air filter cover.

2. Old Fuel

Old fuel can definitely make your Toro mower run sluggishly. This is because gas begins to break down as soon as 30 days after purchasing it.

The ethanol and moisture drawn into the fuel system may leave behind gummy deposits that restrict fuel flow. A power loss will be experienced when the engine doesn’t get enough fuel.

If you find old fuel in your mower, drain the fuel tank and fill it with fresh gasoline. Gas-powered Toro mowers require unleaded gasoline with a minimum 87 octane rating and a maximum ethanol content of 10%.

While Toro mowers manufactured today use a 4-cycle engine requiring straight gasoline, you may still find older Toro mowers with 2-cycle engines being used.

2-cycle engines require a gas and oil mixture in the fuel tank. Read more about choosing the right type of fuel for your Toro mower here.

Add a fuel additive like Sea Foam Motor Treatment to stabilize the gas, reduce moisture in the fuel and clean the fuel system.

It is also helpful to add Sea Foam when you have more gas than you can consume within 30 days. I like to add Sea Foam to every tank of fuel as added protection to the fuel system and engine.

You can find out more about why I like Sea Foam in this guide.

3. Plugged Fuel Filter

A fuel filter strains the fuel as it comes out of the fuel tank to keep dirt and debris from entering the fuel system. When the filter isn’t changed out regularly, the filter will become plugged preventing fuel from passing through the filter.

It is good practice to replace your fuel filter annually when performing your routine Toro mower maintenance. This filter is an inexpensive part that can prevent fuel supply issues and significant engine damage if it fails to strain dirt efficiently.

To replace the filter, shut off the fuel flow using the fuel shut-off valve on the mower or fuel pinch-off pliers if your mower doesn’t have a shut-off valve. Remove the clamps and pull the filter out of the fuel lines and install a new filter.

Pay attention to the arrow you’ll find on the side of most inline filters. The filter must be installed with the arrow pointing in the direction of the fuel flow.

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

4. Clogged Fuel Line

The gummy deposits mentioned previously from running old gas can clog the fuel lines.

Check for a clog in your Toro mower by stopping the fuel flow and removing the end of a section of the fuel hose and placing it in a container. Start the fuel flow to check for good flow out of the fuel line.

When you find a clogged fuel line, stop the fuel flow and remove the section of the line from the Toro mower. Spray carburetor cleaner into the line.

This is to help loosen up the clogs. Blow compressed air through the line to free the obstruction.

If you cannot remove the blockage or you notice your line is dry and cracked, replace it with a new fuel line of the same length and diameter.

5. Dirty Carburetor

Your carburetor is an important component of your mower. It regulates the correct amount of fuel and air allowed in the cylinder to form combustion.

The substances left behind by running old fuel can collect in your carburetor preventing it from providing the fuel needed to run. When this happens, the dirty carburetor can cause your Toro mower to experience a loss of power.

Clean a carburetor that isn’t allowing fuel to get to the cylinder. Before you tear your carburetor apart, remove the air filter and spray carburetor cleaner into the air intake.

Start your engine to see if it will run. You need to clean your carburetor if it runs but won’t stay running. Refer to the article to find step-by-step instructions to clean your Toro carburetor.

6. Bad Spark Plug

A fouled spark plug can cause an intermittent spark that may result in a loss of power. Inspect your spark plug for signs of carbon, dirt, and oil buildup on the tip.

If you find a dirty or damaged spark plug, I recommend replacing it with a new one to ensure you’re running a good plug in the mower.

Alternatively, if it’s only dirty and not very dark in color, you can attempt to clean it with a wire brush and reuse it.

7. Low Engine Oil Level

When the engine oil level in your Toro mower’s crankcase is low, you’ll experience a loss of power. You could be low on oil if you didn’t add enough oil into the crankcase during your last oil change.

It could also be the result of an engine oil leak or from burning oil due to running the wrong oil viscosity.

It’s never good to run your mower low on oil. If you do and it’s not caught soon enough, significant engine damage can result in a large repair bill or even an engine replacement.

Engine oil is required to keep the internal engine parts lubricated. When there is a lack of lubrication, friction builds from the moving parts and creates extreme heat.

This can cause your Toro mower to overheat and smoke from burning oil and melting parts.

Check your engine oil level before each use of your Toro mower as a precaution. I understand it’s one more step in your busy schedule, but it doesn’t take long and can help you catch oil leaks and engine problems before they develop into significant problems.

To check your engine oil, remove the dipstick and use a clean rag to wipe the oil off the stick. Replace the dipstick and then remove it. Check the oil level. The oil needs to be at the full level on the dipstick.

If it is not, add fresh engine oil until it is full. Do not overfill it or you’ll run into more problems.

If you continue to have problems with your engine after you refill it to the full level, you should have the engine diagnosed by an experienced small engine mechanic.

A low engine oil level may have caused internal damage that can’t be fixed by adding a little fresh oil.

8. Too Much Engine Oil

Overfilling the crankcase with engine oil will cause your engine to smoke. Increased pressure builds as a result of too much engine oil and oil can be pushed into the cylinder through the valve train.

When this happens, a bluish-white smoke is emitted when the oil burns in the cylinder.

This thick cloud of smoke can plug your air filter causing running issues because your engine isn’t able to get the clean air it needs. Check your air filter and your spark plug, and clean or replace them if needed.

Continuing to run your Toro mower with too much oil can cause seal damage, the engine to hydrolock, and a bent piston rod.

Remove a Little Engine Oil

You can remove the oil by loosening and quickly tightening the drain plug to only allow a little oil out of the engine. You can also remove oil from the oil filter or out of the oil fill area using a turkey baster or oil evacuator.

9. Dirty Engine Cooling System

The engine uses air to keep it cool. Air is circulated around the engine block and cylinder head.

It’s important to keep the cooling fins clean so they don’t become plugged with grass clippings and mud inhibiting the amount of air that is pushed around the engine. Replace damaged cooling fins.

Just like you need to remove debris from collecting in your cooling fins so the engine doesn’t overheat and experience a loss of power, the same is true of cleaning around the engine shroud and air intake areas.

10. Blocked Air Passageways

The engine needs to be kept cool to prevent overheating and losing power. Make sure your engine has good air circulation by removing any grass clippings, dirt, and debris that may be collecting around your engine.

Remove all the debris that has been collected under your engine shroud. Make sure the heat shield is securely in place.

11. Fast Ground Speed

Trying to complete your mowing task quickly so you can move on to relaxing for the day sounds like a good idea, but it may be the cause of your Toro mower losing some power.

Mowing your lawn at a fast speed can put an extra load on your mower when mowing thick, wet, or tall grass.

Operate your Toro mower at a slower speed to account for your mowing conditions so you put less strain on the mower. This includes slowing down when mowing on an incline.

12. Cutting Wet or Tall Grass

Avoid cutting grass that is damp or wet. Wet grass causes your engine to work harder.

It is more susceptible to clumping and sticking to the underside of the mower deck. For the best cutting performance, mow your lawn when the grass is dry.

It’s best to keep your grass cut at a manageable length by regularly cutting your grass. If your grass does get very tall, your mower can bog down when attempting to cut it.

As much as you try to keep your grass mowed, there are times when the grass does get tall.

When mowing tall grass, you should double or triple-cut your lawn for the best results. Do this by adjusting the mower deck to its highest setting for the first cut and then lowering the cutting height for the next cut.

13. Plugged Mower Deck

The area under the mower deck must be kept clean and free of debris to avoid overworking the engine and experiencing a loss of power. When the Toro mower blades are rotating under the mower deck, they should be able to move freely.

A packed mower deck puts extra strain on the engine when it is required to work harder to turn the blades through the debris. Keep your mower deck clean by regularly scraping it to remove debris.

This is not only good for your engine but also for avoiding a terrible cut.

14. Dull Mower Blades

Dull mower blades magnify a plugged deck problem. Adding worn blades to a plugged deck that is already experiencing a loss of power will require additional engine power to turn the blades.

Check your blades and sharpen or replace them if needed. You can find more information on inspecting your blades and the sharpening process here.

Still Having Problems with Your Toro Lawn Mower?

It would be great to own a problem-free lawn mower, but it’s never the case. No matter what brand mower you own, you’re going to run into problems the longer you own it.

To help you troubleshoot your mower problems, I have put together a list of common problems along with causes and solutions to fix them. Check out Common Toro Lawn Mower Problems and Solutions to learn more.