Lawn Mower Smoking and Sputtering- How to Fix [DIY Solution]

Have you ever experienced that your mower is smoking black or white? It’s truly an embarrassing situation for all who just started their lawn mowing but stopped due to smoking and sputtering. If you want to fix the problem, you first need to know why the lawn mower is smoking and sputtering.

Smoking and sputtering can occur in a lawn mower due to some possible reasons. It may happen due to incomplete combustion, overfilling the lawn mower with excessive oil, tipping it the wrong way, and inflating the gasket.

Don’t worry; if you find such problems in your lawn machine that can cause smoking and sputtering, you can fix them yourself. Let’s dive into the topic.

4 Reasons Why You Lawn Mower Smoking and Sputtering

Your lawn mower is misfiring, putting out black smoke? Let’s know the key reasons below.

1. Overfill With Engine Oil:

Like a car, you shouldn’t overfill your lawnmower with excessive engine oil because it can overheat the engine.

Your engine might get locked up due to excessive engine oil in your lawn mower. In that case, the engine will not run well and cause smoke. It is one of the most common things that you may come across.

Note: You will face the sputtering problem in your lawn mower due to using old or wrong fuel.

Tip: Check the air filter to ensure it isn’t overfilled with oil. You can use the dipstick to check the oil level. 

2. Tip Over the Lawn Mower in the Wrong Way:

Another common reason for lawn mower smoking and sputtering is tip over the lawn mower incorrectly. If you tip the mower the wrong way, the chances are that the oil will leak into the tube and restrict the fuel line.

Or, if the oil moves into the breathing tube, oil can restrict the air filter. Thus the engine can’t run and cause the problem.

Tip: You can replace the faulty tube with a new one or replace the air filter.  

3. Inflated Gasket:

If the gasket gets a little crack, it will start leaking out the oil, clogging the fuel line and restricting the engine’s running. Ultimately, the engine will be overheated and cause smoking.

Tip: You can repair the gasket crack or change the faulty one with a new head gasket.

4. Incomplete Combustion:

It happens because of incomplete combustion. Generally, sputtering or smoking is caused by two things.

  • The first one is your spark plug either fouling or not working properly. There is no appropriate gapping.
  • The second reason can be the air filter when it is dirty and not working properly. It can cause incomplete combustion.

Basically, the reason why it causes incomplete combustion (when the spark plug or filter is not working properly) is because of the fuel. The fuel is coming through the lawnmower, but it is not properly burning.

Because of the incomplete fuel burning, it blows out black smoke; your lawnmower will run roughly. You may also experience your lawn mower losing power or backfiring etc.

How to Troubleshoot the Lawn Mower Smoking and Sputtering? Easy 2 Methods

To sort out the problem, the first thing that you usually check is to check the air filter. You should ensure that it is clean and clear, and after that, you must check the spark plug.

Inspect if the plug is really black or carbonated. You may need to change the plug or clean it. Also, inspect the gap and ensure that there is an appropriate one on the spot.

Here, I will explain the process of checking and cleaning the air filter and then the Spark plug. So, let’s come to the diagnosis process.

Method 1: Check and Clean the Lawnmower Air Filter

Step 1- Check the Airport

First of all, you should check the airport. It is all nice. Ensure it should be clean enough. Unscrew the screws and tap the box to open the airport.

Check the Airport

Step 2- Inspect the Airport

Once you have removed the airport, inspect it thoroughly. Make sure there should be no dust in excessive amounts.

Inspect the Airport

Step 3- Take off the Foam

For proper cleanliness, take out the foam from the filter and check it thoroughly.

Take off the Foam

You can see old lawn clippings, dust, and everything like that. Such hurdles add to misfiring and incomplete combustion.

It is a non-effective air filter that deteriorates the overall performance. So you need to clean it. Clean it thoroughly and ensure all the debris and grass particles are removed.

Once it is properly cleaned, reinstall it at the previous place. Check the lawnmower; if it is still sputtering or smoking, then the problem is with the spark plug so check for the spark plug.

Method 2: Check and Fix the Lawnmower Spark Plug?

Here I will teach you three simple steps to check clean and then replace the spark plug if needed. It will boost the engine performance.

Things You Will Need:

  • Spark Plug Wrench
  • Hex turning tool
  • Spark plug wire brush
  • Spark plug gapping tool

Step 1- Read the Manual

It will help you to finish your job quickly and perfectly if you read the instruction manual.

Read the Manual

Step 2- Check for Spark Plug

First, you must remove the spark plug to check it thoroughly.

remove the spark plug to check it thoroughly.

Start with removing the spark plug wire. You can grip it and go ahead and pull it straight off of the spark plug.

Then move it out of the way, get a spark plug wrench, and place it over the spark plug until you feel it engaged.

 over the spark plug until you feel it engaged.

Then install the hex turning tool and loosen the spark plug. You may need to turn it on for a few seconds.

You may need to turn it on for a few seconds.

Once it is removed, you can inspect the spark plug. You can see it is dark and covered with carbon. You can restore it after cleaning the carbon. Also, check for the gap.

You can see it is dark and covered with carbon.

Step 3- Clean the Spark Plug

Take a soft wire brush; it would protect your spark plug from damage.

Clean the Spark Plug

While cleaning it with a brush, start from the outside edge of the spark plug and then turn it. You will be able to access the entire surface and also check for the spark plug gap.

That looks fairly good now; check for the spark plug gap. You should use the spark plug gapping tool.

Insert the tool between the open and gap in the spark plug on the smallest end; this is point zero to zero.

Then slide the spark plug up until it stops. Check the measurement; it should be less than zero

it should be less than zero

Reinstall it, but if needed replacement, go ahead to replace it with a new one.

Step 4- Replace the Spark Plug

Take a brand new Spark plug that should be compatible with your engine brand. Then take a spark plug wrench to remove the older one and install a newer spark plug.

Place the new spark plug at the end of the wrench and carefully turn the spark plug. Turn it until you feel the threat set, and keep it turning slowly until the spark plug stops.

Tighten it some more to ensure correct installation.

Once you have tightened it, finally reattach the spark plug wire.

Switch on the lawnmower to test, hope there will be no sputtering or smoking issue. You have done your job well.

Read Another Article About Spark Plug: 5 Lawn Mower Bad Spark Plug Symptoms to Look Out For!

Frequently Asked Questions(FAQs):

What are signs that a lawn mower air filter is bad?

You may notice poor engine performance if there is a problem with the air filter. Common signs include hard starting, random misfire or sputtering, stalling, smoking, and failure of fuel system parts.

What does it mean when my lawn mower smokes grey or blue?

If you notice your lawn mower is smoking blue or grey smoke, it means the problem is with the engine. Your engine is burning the fuel inside the combustion chamber. Maybe there is leakage of valve seals or bad piston rings.

Why is my lawn mower smoking white?

There may be an issue with the combustion chamber. Coolant or water is vaporized in the combustion chamber, producing white smoke.

What happens if my lawnmower is sputtering or smoking?

If your lawnmower smokes, there is no harm except an unpleasant mowing experience. It may cause frequent engine stalling if you do not immediately remove the issue.

Final Verdict

Lawnmower smoking or sputtering is a common issue you can fix in a couple of minutes. Air filters, combustion chamber, spark plugs, fuel quality, and poor wiring can be possible reasons for smoking.

You should immediately identify and fix the issue for a smooth mowing experience. If you find it tough to solve the problem, then please don’t hesitate to take professional help.

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