Lawn mower plug fouling. How To Clean a Fouled Spark Plug? Causes, Symptoms, and Fixes

How To Clean a Fouled Spark Plug? [Causes, Symptoms, and Fixes]

When a spark plug gets fouled, it will cease to fire and burn the air-fuel combination. As a result, a misfire is produced, causing a loss of power and fuel efficiency and an increase in tailpipe hydrocarbon (HC) emissions.

As a driver, one of the issues you are likely to experience is fouled spark plugs. So, how do you clean a fouled spark plug?

How To Diagnose and Read the Color of Your Spark Plug

To address this issue, abrasives such as a file or sandpaper may be used to efficiently clean your spark plugs. However, if you don’t have either one, a blow torch could also do a fantastic job.

Keep reading to get all the information you need on how to clean a spark plug.

What is a Spark Plug Fouling?

When your spark plugs get dirty or contaminated, the performance of your engine suffers. A fouled or faulty spark plug has gotten coated with a material such as oil, petrol, or carbon.

It can be caused by blisters due to overheating. Driving with clogged or damaged spark plugs can create a slew of issues with your engine.

Why Does Spark Plug Foul Get Dirty?

These plugs are intended to clean themselves to a certain extent. So when the engine is running, the ceramic coating that covers the electrode heats up and burns off every oil or fuel ash accumulation. Otherwise, it will clog the spark plug.

Yet, the spark plugs must not be overheated to the point of detonation or pre-ignition. So, you can only use the spark plugs that are recommended for your engine.

In fact, full-speed and lengthy rides are good for spark plugs since they produce heat, which helps keep the spark plugs clean.

However, short excursions, city travel, and idling for an extended period are not healthy for the spark plugs as they can’t reach the required temperature to burn off all of the deposits.

What Causes Spark Plugs to Foul Quick?

Spark plugs foul fast because other faults within your engine lead them to wear out prematurely. Check that your valves are correctly sealed and that your ignition system is operational.

If you have oil-fouled spark plugs, inspect the PCV valve. A faulty PCV valve may allow harmful fumes to travel through the piston rings and deposit oil on your spark plugs.

You should also ensure that your automobile is not running too strongly and that the fuel-air combination inside the combustion chamber is enough. This will ensure that your spark plugs have a long life and that you wouldn’t have to replace them.

Spark Plug Foul Visual Symptoms

If your spark plugs are clogged or damaged, they can cause various issues such as decreased gas mileage, intense vibrations, engine misfires, and difficulty starting the engine. So, if you’re having engine trouble, inspecting your spark plugs is a Smart place to start.

Reduced Engine Power

There is no doubt that if your spark plugs are faulty or dirty, your gas mileage will drop. So if you find any of these problems, you should evaluate them.

When your automobile is running, the O2 sensor in front of the exhaust measures the exhaust gasses.

Also, if your gasoline somehow doesn’t burn quite well, the O2 sensor will verify the measurements and determine that your exhaust fumes are not acceptable.

As a result, the engine will be told to pour additional gasoline into the combustion chamber. gasoline equals more unburned fuel and more trips to the gas station.

Strong Vibrations

The constant wear and tear from engine vibration can cause the electrical connection at the spark plug to loosen.

This raises the voltage necessary to ignite the spark plug, potentially damaging the ignition coil and the spark plug wires.

lawn, mower, plug, fouling

Additionally, Worn or filthy spark plugs can cause a petrol automobile’s engine to misfire in one or more cylinders, causing vibrations while the car is idle or driving.

Hard Engine Start

One other sign of clogged spark plugs is trouble starting the automobile. When there is no spark within the combustion chamber, the gasoline will not burn, and the engine will not start.

This can be caused by clogged spark plugs, poor compression, faulty connections, faulty coils, a faulty starting motor, or a dead battery.

In fact, when you have problems starting your automobile, the problem can be caused by various factors.

So, if the spark plugs are black from carbon or coated with oil, there is an insufficient spark. However, if the spark plugs aren’t in good condition, you should replace them.

Engine Misfire

Engine misfires are among the most prevalent issues that automobile owners, like you, confront when their spark plugs are faulty or clogged.

This is due to two conditions that might cause the cylinders to function unevenly and cause the engine to misfire; lack of spark or a spark that is insufficiently powerful or delayed.

When this happens, you’ll see that the engine’s operation is radically different and does not function smoothly.

These misfires are loud out from the exhaust and noticeable when you push the throttle. So, there should be some loud bangs when a cylinder is misfiring.

How to Identify a Foul Spark Plug?

When looking for a faulty spark plug, start with the firing tip. It might be a fouled spark plug coated with a foreign material such as petrol, oil, or carbon.

Instead of bridging the gap and starting the engine normally, this coating will simplify the voltage to follow down the insulator nose, seeping back down into the metal shell and producing no spark.

Several things must be addressed. One of them is if the air-fuel ratio is overly high, which can be caused by faulty carburetor adjustment or a badly performing injection system. Aside from that, a filthy or clogged air filter can also contribute to this rich state.

Another thing to consider is when piston rings or valve seals wear, this will allow oil to flow into the combustion chamber and cause oil fouling.

How to Clean a Foul Spark Plug?

Spark plug fouling can be caused by a variety of circumstances. As a result, cleaning them differs depending on what caused the spark plugs to foul.

Carbon Foul

If you notice a lot of carbon build-up on your spark plug, it signifies your engine is frequently misfiring or is running too richly.

As a result, the spark plug cannot ignite all of the gasoline spilled into the cylinder. Hence, the carbon on the spark plug accumulates.

Causes Of Spark Plug Fouling | Maintenance Minute

It is advisable to replace the fouled spark plug to resolve this issue. Also, ensure that all of the other ignition components are operational.

Check the carburetor if you have a carbureted automobile and the fuel injectors if you have a fuel injection car.

However, if you have a direct injection vehicle, such as an Audi, BMW, Hyundai, Kia, Mazda, Mercedes-Benz, Nissan, Lexus, Saab, Subaru, or Volkswagen, this is typical. Carbon accumulation happens as a result of their engineering and construction methods.

Coolant Foul

In another situation, a blown head gasket indicates that your vehicle is burning coolant. Vapors may be produced by the coolant in the combustion chamber. Hence, these fumes can enter the spark plug, cause rust to form on the threads, and harm the electrode.

To resolve this issue, you will need to change the head gasket, and even the spark plugs with new ones.

This will ensure that your problem has been resolved and that you have no more problems with the ignition system or the spark plugs.

Oil Foul

If you see that the spark plugs have a lot of oil over them, it indicates that the valves are leaking. This will cause the valve seals to fail to seal correctly, allowing oil to leak into the cylinder and ignite. When oil burns, it produces carbon in the combustion chamber and fouls the spark plugs.

Another cause of oil on your spark plugs is a faulty PCV valve. When this valve becomes blocked, it prevents crankcase pressure from building up. This ultimately allows the oil vapors to pass through the piston rings and leave an oily mess on your spark plug.

Hence, the simplest solution is to replace the spark plugs and leave them for good. Sadly, this is not a long-term fix since your spark plugs may foul and become defective again.

So, the problem can be solved by removing the head and inspecting the valves. Examine their situation and then take action to permanently resolve this issue. Don’t forget to check the PCV valve as well.

Ash Deposits

The accumulation of ash in spark plugs is a very regular phenomenon. These ash deposits might accumulate over time and lead your spark plug to malfunction.

Generally, these ash particles can be formed by the combustion chamber burning oil or fuel additives.

If these deposits cause a significant accumulation. They can obstruct the spark and hinder the spark plug from functioning correctly. This can lead to the development of misfires.

Remove the spark plug and use sandpaper to scrape out the ash deposits to resolve this issue. Check for any additional impurities, and your spark plug should be operational in no time.


Blistering of spark plugs is possible. So If your spark plug is blistered, you’ll see some bubbles on it. Other than that, it will also have a slightly brownish tint.

A poor fuel-to-air combination causes spark plug scorching. specifically, a low fuel-to-air combination. Blisters seen on your spark plugs are one of the consequences of running your automobile too low.

So, you must ensure that your fuel-to-air mixture is right and that your engine is operational. If you have a carbureted automobile, you may achieve this by adjusting the carburetor. However, if you have a fuel injection system, a simple computer tweak will do the work.

Fuel Foul

If your spark plug is saturated with fuel, it signifies your engine is running too heavily. Hence, the air-fuel combination must be altered, and you must immediately address this issue before it worsens.

So, if you are experiencing this issue, it is a Smart option to inspect the carburetor if you are driving a carbureted vehicle.

Perhaps the carb spills an excessive amount of fuel into the combustion chamber. As a result, there is petrol on the spark plug.

The ignition wires should also be checked. If they aren’t good, it implies they’re not doing their job correctly, which leads to a cylinder malfunction.

If you own a fuel-injected car, check the condition of the coils to ensure they are in correct working order. Misfires and gasoline on spark plug issues might occur if the coil is faulty.

Some other consideration is the injectors. Each time, the injectors must deposit the correct fuel volume into the cylinder. When they’re not doing it, this indicates that something must be broken with your fuel injectors.

They may be inspected using an OBD2 scanner tool connected to your OBD2 port. However, keep in mind that this troubleshooting may necessitate using a more sophisticated scanner to analyze the output of each injector.

As more modern scanners are more expensive, you’ll need to have a budget for them. If you don’t have the money, you may take your car to a shop, and they will diagnose the injector problem.

Gapped Foul

Gap bridges in spark plugs happen when the sediments that link the electrodes become too wide, prohibiting a spark from occurring within the engine cylinder. This might be caused by an accumulation of oil or ash.

The answer to this problem is straightforward. You only have to change the spark plug. However, if you don’t want to replace the spark plug, simply pull it out and wipe it all with sandpaper. This will ensure that the carbon deposits on the spark plug have been removed.

Tips to Avoid a Fouled Spark Plug

Aside from treating the root cause of your spark plug fouling, there is another technique to avoid spark plug fouling.

Following the primary purpose of a spark plug, the firing end temperature of the spark plug must be kept low enough to avoid pre-ignition yet high enough to prevent fouling. This is called “thermal performance,” and it is governed by the chosen heat range.

Frequently Asked Questions (FAQs):

Aside from the information provided above, you might have other issues regarding the fouling of your spark plug. So, here are the most frequently asked questions and the answers to them.

Will fouled spark plugs clean themselves?

The answer is yes. Spark plugs are designed to self-clean. So, stepping on the gas and driving your automobile for a fast 20-minute drive on the highway would do the thing in cleaning your clogged spark plugs.

Can you still use fouled spark plugs?

Yes, you can. Your fouled plugs can be cleaned and reused. Every fifty hours, clean, gap, and test spark plugs. If you obtain a clogged plug, use carb cleaning or sandpaper to remove the deposits. Use a brass wire brush to remove difficult deposits (the brass will not harm the electrode).

What is the quick fix for fouled spark plugs?

If you have only driven your car on occasion, or for short distances, or the engine has remained idle for 15 minutes or longer. It can cause your spark plugs to become clogged and your automobile to misfire.

So, you must take it onto the road, accelerate aggressively, and run it for 15 to 20 minutes at the highest speed limit permissible in your location. When the fouling is not caused by unusual means, it will automatically clean the plugs.

If it still misfires due to fouling, the plugs may be unclean or worn. You may also remove the spark plugs and check them, clean them if feasible, or replace them.

How do you get debris out of your spark plug?

There are various ways to clean the spark plug. You can either use the items below alone or one after the other for the greatest results.

  • File
  • Blowtorch
  • brush made of wire (wire brush)
  • 220 grit sandpaper
  • Airgun (for remaining debris)

What happens when you leave a fouled spark plug?

When you leave a filthy spark plugin, it stops working properly. If your spark plugs are fouled, the engine will run rough, lack power, consume more gasoline, or perhaps fail to start at all.

Takeaway: Cleaning Fouled Spark Plugs

After 20,000 to 30,000 miles, spark plug fouling might develop. Whether you want to clean or replace an old plug, it must be done correctly since spark plug fouling can create serious automotive problems.

Any material that accumulates in the spark plug hole or combustion chamber due to cleaning might harm the engine and lead to more significant issues, such as accidents.

In brief, to clean a spark plug safely, use a wire brush or spray-on plug cleaner made exclusively for this ignition component. A strong knife can also be used to scrape away stubborn deposits. However, it is important to remember that you should never use a shot blaster or abrasives to clean a spark plug.

How to Tell If a Lawnmower Spark Plug is Bad?

It’s a real mood destroyer when you are mowing your lawn, but your mower won’t start easily or won’t start at all. But if you know the reason behind the problem, there is often an easy fix. A highly likely cause of your engine having trouble starting could be a bad spark plug. Lawnmowers with gasoline engines need spark plugs to provide ignition to the engine. A spark plug is a small, simple device with a center electrode and a side electrode. A spark made to flow through the small gap between the two electrodes ignites the cylinder’s air-fuel mixture. Mowing becomes problematic when the spark plug is bad. You can judge symptoms if your spark plus is having problems and needs a change.

How to Tell If a Lawnmower Spark Plug is Bad:

  • The engine is difficult to start. This is the most common symptom of a bad spark plug.
  • The engine shows poor performance and keeps stopping while mowing.
  • Unusually high fuel consumption.
lawn, mower, plug, fouling

Now that you know the most common symptoms associated with a bad spark plug let’s go into the details of why a bad spark plug may cause these problems and what to do when these symptoms emerge.

  • 1 What does a Spark Plug do
  • 2 Symptoms of a Bad Spark Plug
  • 2.1 Engine Has Trouble Starting:
  • 2.2 Bad Performance:
  • 2.3 Unusually High Fuel Consumption:
  • 3.1 Understanding Problems:
  • 3.2 Spark Plug Gap:
  • 6.1 Step 1: Get a similar Spark Plug
  • 6.2 Step 2: Disconnect the Spark Plug
  • 6.3 Step 3: Remove the Spark Plug
  • 6.4 Step 4: Put the new Spark Plugin
  • 6.5 Step 5: Reconnect the Spark Plug wires

What does a Spark Plug do

Though a spark plug is relatively small in size, it plays a vital role in a gasoline-powered engine. The spark plug in a lawnmower’s engine performs the same job as in an automobile engine.

Unlike most parts of an engine that perform mechanical roles, a spark plug is an electrical device. Its central electrode receives a high voltage from the ignition coil or the magneto. That’s why it is the live electrode. The side electrode doesn’t receive voltage from any source and is a ground electrode. When a high voltage is provided to the central electrode, a high potential difference is created between the two electrodes, which allows a spark of current to flow between the electrodes. The spark plug is fitted in the engine cylinder head, and the spark ignites the air-fuel mixture. Combustion of the air-fuel mixture provides energy for the engine to run.

If the spark plug cannot do its job correctly, there will be no ignition or improper ignition, causing all sorts of problems. In the worst case, your engine might not start at all.

Symptoms of a Bad Spark Plug

You know the main symptoms now; let’s get into their details so that judging becomes more comfortable for you.

Engine Has Trouble Starting:

Like said before, it is the most common symptom associated with a faulty spark plug. An engine with a bad spark plug won’t start normally. If you are using a push mower, it will take many pulls on the starter rope before the engine starts. Likewise, if you are using a lawn tractor, a single turn of the key won’t be enough to start the engine.

Now that you know what a spark plug does, the explanation of this symptom becomes relatively easy. A faulty spark plug generates a spark too weak to ignite the air-fuel mixture coming from the carburetor. As more mixture enters the cylinder and only a tiny portion gets ignited, the engine gets flooded by the entering mixture.

Bad Performance:

Even if the engine with a faulty spark plug finally starts after many tries, it will fail to keep running for a normal period. Because the spark plug is not functioning correctly, the engine will die out immediately or stop mowing.

When the engine keeps dying out, it needs to be started again and again. After each try at starting the engine, starting becomes more difficult as the engine is getting warmer. This is because heat causes expansion in metals, which widens the gap between the two electrodes, and the strength of the ignition spark further decreases.

Other performance-related problems associated with a faulty spark plug may include the engine sputtering, popping, or missing. Misfires cause these problems.

Unusually High Fuel Consumption:

If your lawnmower is taking more fuel for the same job than usual, one reason might be a bad spark plug.

With a bad spark plug, ignition is not efficient, and the fuel is not combusted correctly. This decreases the fuel efficiency of the mower, thereby increasing fuel consumption.

Another way to judge that your mower is not burning and consuming fuel efficiently is odor. Because of a bad spark plug, the fuel is not burned correctly, and raw gasoline is created as the mower is in operation.

lawn, mower, plug, fouling

Checking the Spark Plug:

A faulty spark plug will give you clear enough symptoms of the problem, but you don’t necessarily need to wait for the signs. You can check the spark plug periodically so that you are always aware of your mower’s spark plug health. There are several criteria on which you can judge the health of your spark plug. Once you know your spark plug is not in perfect condition, you can either fix it or change it.

Understanding Problems:

Stay well informed about the problems an engine might have if the spark plug is bad. You can learn about these problems from the user manual or easily from the internet.

If the engine is not starting at all or not starting correctly, immediately check the spark plug. If the engine shuts down during operation, check the spark plug. If you are forced to add fuel, again and again, check the spark plug.

Spark Plug Gap:

The spark plug gap is the gap between the two electrodes. The gap of the spark plug must be right. Even a small deviation from the designated width can cause problems.

During operation, the engine becomes hot, which causes expansion, and the gap increases. When the engine is cold, contraction occurs, and the gap reduces. Over time, the electrodes develop residual stresses and strain the gap is permanently distorted from its right width. The wrong gap reduces ignition strength. Due to this reason, you should let the engine cool down a bit if you’ve been trying to start it again and again and let the gap.

The spark plug gap can also change during shipping or handling or if the plug falls on the floor, or if the anode gets thinner. So, always check the gap before installing a spark plug.

The spark plug gap is something that can be adjusted. If your engine has a problem starting, check if the spark plug gap is right. If it’s not, you can adjust it to match the spark plug packaging or engine manual’s gap specification.

When to Change Spark Plug?

According to experts, a home-owned lawnmower’s spark plug needs to be changed once per season or after 25 hours of operation.

An acceptable practice can be to be cautious about the problems and change the spark plug as soon as any problem appears.

To stay safe, though, and avoid any problems, it’s good to change the spark plug once a year.

Cleaning the Spark Plug:

If the spark plug is corroded too badly or has carbon burns or burnt deposits, all you can do is change it. But if the spark plug is just wet from too much gas or oil buildup, it can be cleaned.

The live electrode (central electrode) should have an even and flat surface at the top. If its top surface is damaged, the spark plug should be changed. If there are any cracks on the spark plug’s porcelain sheath, the spark plug needs to be changed.

The plug can only be cleaned if it is wet from gasoline or oil, and there is no visible physical damage.

Replacing the Spark Plug:

The spark plug in a lawnmower is located under the black spark plug wire. Disconnect the wire and take the plug out for inspection.

Follow these steps for replacing a spark plug:

Step 1: Get a similar Spark Plug

Ensure the replacement plug is the same size and with the same specifications as the one being replaced.

Step 2: Disconnect the Spark Plug

Disconnect and clean around the spark plug wire.

Step 3: Remove the Spark Plug

Take the plug using a wrench out and inspect the electrode for any signs of engine problems. If it’s too dry or wet, there might be a problem with the carburetor.

lawn, mower, plug, fouling

Step 4: Put the new Spark Plugin

Put the new plugin by first turning it in by hand to ensure that you don’t cross-thread. When it can’t be turned by hand anymore, use the wrench for further turning.

Step 5: Reconnect the Spark Plug wires

Connect the spark plug wire back.

Final Remarks:

A faulty spark plug can cause problems to the lawnmower engine, making it almost impossible to operate. But if you have basic knowledge of a spark plug’s function and how it works, and the symptoms of a bad spark plug, the problem can be easily solved. Problems like distorted gap and the electrode being wet can be fixed, while if there is any physical damage to the plug, it has to be replaced.

About Us

This blog is written by a group of Garden Tool enthusiasts. Together we put a lot of effort into the maintenance of our gardens over the last few years, we become obsessed with it. Nearly every weekend you will find us doing small or big jobs or just enjoying our garden. We like to help other people maintaining their garden and find cool products to write about.


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How to Tell When it Is Time to Change Bad Spark Plug in a Lawnmower

A lawnmowers spark plug plays a critical role in how the engine operates. If it fails to fire, or doesn’t work properly, your lawnmower will not work.

But how to tell if a lawn mower spark plug is bad?

There are a few ways to diagnose a bad spark plug. The following article will explore Symptoms Of bad lawn mower spark plug, and When How To change a spark plug in a lawn mower.

  • 1 What Does A Sparkplug Do?
  • 2 What Are Some Signs Of A Bad Spark plug?
  • 3 how to tell if a lawn mower spark plug is bad?
  • 4 how to change a spark plug in a lawn mower?
  • 4.1 Step 1: Disconnect the lawnmower’s sparkplug wire.
  • 4.2 Step 2: Use the spark plug socket to carefully remove the spark plug.
  • 4.3 Step 3: Examine the sparkplug, paying close attention to the electrode.
  • 4.4 Step 4: Double-check the new sparkplug.
  • 4.5 Step 5: Install new spark plug
  • 6.1 Can Dust And Debris In The Fuel Tank Cause A Problem?
  • 6.2 Cleaning Or Replacing the Air Filter
  • 6.3 Winter Lawnmower Maintenance Helps Preserve The Engine And Spark Plug
  • 6.4 Stabilize the Fuel
  • 6.5 Clean the Deck
  • 6.6 Spring Lawnmower Preparation Is Essential
  • 6.7 Change The Oil
  • 6.8 Lubricate the Moving Parts

What Does A Sparkplug Do?

It’s essentially an electrical device that directly draws power from a special induction coil that is connected to the flywheel of the engine.

When it is operating properly it ignites the fuel and air mixture in the combustion chamber. Without it, there is no way to burn the fuel and the piston that drives the mower’s blades simply will not work.

While spark plugs are designed to be durable, and their construction is quite simple, they do have a finite lifespan.

As they start to degrade, or physically deform from excessive use, the spark plug tends to fire intermittently.

What Are Some Signs Of A Bad Spark plug?

As time goes on a failing spark plug could make it much harder to start. This could manifest as a frustrating number of pulls on the drawcord.

In the case of a riding lawnmower, it could take a lot longer for the starter motor to turn the engine over, which could also start to tax it or even affect the life of the battery.

A badly degraded or deformed spark plug could cause the lawnmower’s engine to stall. This is especially likely to happen if it bogs down in tall grass.

A riding lawnmower with a hydrostatic transmission and a bad spark plug could potentially stall out completely when the engine is being taxed by doing something like cutting while going uphill.

how to tell if a lawn mower spark plug is bad?

If you are paying attention, you can usually notice if a lawnmower’s sparkplug is starting to go bad.

A pull mower might take an increasingly longer number of pulls, or a riding mower might take longer than usual to start when you turn the key.

A lawnmower with a bad sparkplug might also start to develop performance issues or consume more fuel than usual. This could even cause a lingering smell of raw gasoline while you are mowing.

A truly bad sparkplug might also show visible signs. Physically the center of the electrode should have a flat top. If you take the plug out and it looks rounded on top or there are some cracks, then it’s probably wise to replace it.

At the same time, some bad spark plugs will also look black from carbon or degraded excess gasoline.

In a pinch, you might be able to lightly clean the plug and gently adjust the gap between the electrodes.

While this might work once or twice, to get you through a mowing session, you should still consider replacing the plug.

how to change a spark plug in a lawn mower?

Spark plugs have a limited lifespan. So, it’s unrealistic to expect it to last forever.

However, making sure that you properly maintain the lawnmower’s engine and other components can reduce the conditions that can prematurely shorten the spark plug’s lifespan.

It’s also worth bearing in mind that seasonal maintenance is just as important as periodic in-season maintenance.

Beware Dust And Debris

Dusty, dry conditions can potentially affect how a lawnmower performs. Dust and even excessive airborne pollen can start to clog the air filter.

When this happens the fuel-air ratio in the engine’s combustion chamber can lead to premature carbon buildup in the carburetor or around the spark plug.

Can Dust And Debris In The Fuel Tank Cause A Problem?

At the same time dust that gets into the fuel tank through the breather on the gas cap or when you open the cap to refill the tank can become a problem.

As it settles lower into the tank these tiny particles can start to collect and congeal. If you run the tank low or completely dry during a long mowing session, this debris can be sucked into the fuel line.

Not only can this impede the passage of fuel into the system, but it can also start to clog the lawnmower’s fuel filter.

Cleaning Or Replacing the Air Filter

Air filters naturally clog over time. In a certain light, it’s their job. When it is functioning properly, the air filter is tasked with catching any dust and airborne debris before it makes it into the carburetor.

As debris starts to buildup, it can rob the lawnmower of the air it needs to efficiently ignite the fuel-air mixture in the engine’s combustion chamber.

Excess fuel and other debris can then damage or corrode the spark plug.

With some older, gas-powered trimmers and lawnmowers, the air filter is little more than a piece of soft flexible foam.

To clean it you simply loosen the long, threaded bolt that holds the lid in place. You can then wipe off any noticeable debris with a clean piece of paper towel or a shop rag.

If you have a can of air or a shop air compressor, you might be able to blow off any stuck-on debris.

Some newer gas-powered push mowers and riding lawnmowers have more sophisticated air filters and air cleaner systems.

In a case like this, you should check the part number in the owner’s manual. If you don’t have it, the air filter itself might have something stamped or printed on it.

When in doubt, you should be able to easily take it out and bring it with you to the auto parts store.

There are even some discount retail chains that have an automotive department stocked with common lawn mower air filters.

Winter Lawnmower Maintenance Helps Preserve The Engine And Spark Plug

If you live in a part of the country where it gets cold in the winter, or the grass merely goes dormant, then you will need to take some measures to ensure the lawnmower is stored away properly.

Stabilize the Fuel

Fuel stabilizer is very important when storing a lawnmower for the winter. Not only does it help prevent the octane of the gasoline from degrading, but it also reduces the chances of water settling out of the fuel.

Personally, I try to run the fuel tank very low on the last mowing session of the fall. Then I take a small siphon and suck out the last quarter of a tank of gasoline.

This helps suck out some of the dust and other debris that might have found its way into the tank during the summer.

Then I mix fuel stabilizer with fresh premium gasoline in a separate gas can. At that point, I fill the tank until it’s roughly half full.

This allows me to add fresh gasoline with the first session next spring. It’s not something critical, but it helps hedge my bets!

Clean the Deck

I also make it a point to clean away any lingering grass clippings and other organic matter from the underside of the mower deck.

Mice and other small rodents will sometimes be attracted to stuck on grass clippings during a particularly cold and harsh winter.

When they do, they have a knack for chewing on things that they shouldn’t. This includes spark plug wires!

In the case of a riding lawn mower or lawn tractor, I will pull the battery out and bring it into the house.

A battery that is exposed to freezing conditions without proper charging can slowly degrade.

Spring Lawnmower Preparation Is Essential

Spring weather can be fickle. When the trees don’t have any leaves, a rainy day that gives way to a few days of sun can bring your grass out of dormancy with a fervor.

One day you just look outside only to find that things have gotten out of control.

Change The Oil

In a moment like this, it can be tempting to run out to the garage, dump the old gasoline for the snowblower into the lawnmower and just pull the cord.

While you might get away with it once or twice, it’s likely not very good for the long-term lifespan of your lawn mower spark plug or your carburetor.

After a long winter sitting in the garage, your lawn mower’s engine likely needs an oil change, the air filter needs to be cleaned or replaced, and it could do with a good dose of fresh fuel.

If you didn’t add fuel stabilizer to the tank when you put it away, you should add some Iso Heat or a similar fuel conditioner to address any potential water separation in the tank.

Lubricate the Moving Parts

If you have a lawn tractor or riding lawn mower that won’t start, you should also grease the pulleys and bearings. A simple grease gun and two healthy pumps on every zerk fitting will improve operating efficiency.

While this won’t have an appreciable impact on the spark plug, it’s still a wise move for maintaining your investment.

If your riding lawnmower has a battery, you need to make sure it is properly charged before you install it, and try to start the mower for the first time.

From his childhood obsession with gardening to the decade he spent operating a hobby farm, Eric has developed over four decades of experience in self-sufficiency. Not only does this include the organic elements of growing and tending plants, but it also includes a wealth of experience in lawn care, landscaping, and gardening equipment.

Spark Plug Fouling

Spark plugs are the “canary in the coal mine” of the combustion chamber. The electrodes and porcelain can reveal short- and long-term problems if you know where to look.

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Most OE spark plugs have a life of more than 50,000 miles, thanks to electrodes that contain precious metals like platinum and iridium. OEMs consider the spark plugs a part of the emissions system on most modern vehicles.

If the plugs fail sooner than the recommended interval, it’s important to solve the problem before installing new plugs. If you are replacing spark plugs to solve a misfire problem, the car will be back.

But, first, what causes spark plugs to foul quickly? What does a fouled spark plug look like, and what is spark plug fouling?

Carbon Fouling

If the spark plugs have a matte black or grey appearance, it could be carbon fouling — something typically caused by a fuel mixture that is too rich.

During normal combustion, most of the fuel oxidizes and changes into carbon dioxide and carbon monoxide gas. When there is more fuel than oxygen, the carbon in the unburned fuel polymerizes into carbon deposits. These molecules like to stick to the hot spots in the combustion chamber, and this includes the spark plug’s tip and insulator.

Curing the problem will typically point to the fuel system and how the engine is breathing. If a fuel injector is clogged or sticking open, extra fuel can cause carbon problems.

If the mass air flow sensor or oxygen sensors are not accurately reporting the air that’s coming into the engine or the oxygen content in the exhaust stream, it could cause a rich-running condition that can cause carbon to foul the spark plugs.

Another factor is how the air flows past the valves. If the air is restricted or has to flow past carbon deposits on the intake valves, it will be turbulent and disturb the flame front and fuel droplet size in the combustion chamber. This means that the fuel injected into the intake port or combustion chamber will not entirely burn.

Oil Fouling

Oil fouling of a spark plug typically results in a shiny, black appearance. If enough oil is in the combustion chamber, the deposits can build up on the tip, porcelain or shell.

If you can’t determine if it is carbon or oil fouling, smell the plug; it will smell like engine oil. The oil can come from the piston rings, valve stem seals or the positive crankcase ventilation (PCV) system. Leaking piston rings can be diagnosed with a leak-down test. If one cylinder has oil fouling, a relative compression check can help to assess mechanical issues with that cylinder.

Malfunctioning PCV systems are becoming a leading cause of oil fouling in modern engines. These systems have become more than just a spring-loaded check valve. Modern systems can separate oil from the crankcase vapors and electronically regulate when the engine ingests the vapors.

Some PCV systems have a heater to ensure that the valve does not freeze under certain conditions when condensation is present. If the valve does freeze, it can cause higher-than-normal crankcase pressure. This can cause oil to be forced past the valve seals.

If the PCV valve is stuck open, the excess vapors and oil droplets can quickly foul the spark plugs.

A failed turbocharger can be another source of spark plug oil fouling. The seals on the turbine shaft are robust, but they can be victims of heat and poor oil quality. The oil that lubricates the shaft can enter into the pressurized intake and eventually the combustion chamber.

OEMs have issued TSBs concerning excessive oil consumption. Most of these problems relate to cylinder deactivation and variable valve timing.

The main culprit in these problems is vacuum generated in the cylinders that sucks engine oil past the rings and into the combustion chamber. On vehicles with cylinder deactivation, the deactivated cylinder has negative pressure and draws oil droplets in the crankcase past the ring and eventually into the converter. This has happened on some GM and Honda engines.

On some vehicles with variable valve timing (typically on the exhaust and intake cams), the valve timing could produce higher-than-normal vacuum pressures that could suck oil past the rings. This was the case for some recent Toyota, Honda and GM models. The customer would report increased oil consumption that exceeded one quart every 1,000 miles.

Beyond the oil getting past the rings, the oil trapped in the rings can become carbonized and cause damage to the cylinder walls. This can lead to even more damage and more oil consumption. In some cases, the oil consumption results in a low-oil condition that would cause damage to the bearing surfaces.

Coolant Problems

Internal coolant leaks can foul a spark plug and cause a misfire. The problem could be a leaking intake manifold or a head gasket, and the fouled plug might be localized to one or two adjacent cylinders. The burned coolant leaves ashy, white deposits on the electrodes and insulator, creating hot spots that could cause pre-ignition and a misfire code to be set.

When the plug is pulled, it might have a chalky appearance on the ground strap and center electrode. Modern coolants do not cause this type of buildup quickly, due to the reduction of phosphate, zinc and other additives that can contaminate the catalytic converters.

In the past, the converter would become clogged and stop the engine before significant damage occurred.

Unfortunately, formulations mean that drivers can run a vehicle with a coolant leak for several thousand miles, while the plug becomes slowly fouled.