How To Clean A Spark Plug

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Spark plugs play a critical role in any combustion-engine vehicle. From the point you turn the ignition to when you shut it off, each plug is under pressure, being exposed to a hot mixture of fuel, air, and oil in each cylinder.
Over time, they become dirty and fouled. This is why taking care of them is vital.
In this article, we cover the whys, whens, and hows of cleaning spark plugs at home (using minimal equipment).

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How Often Should You Clean Spark Plugs?

Refer to your car owner’s manual for the manufacturer’s specifications and tips for when to clean your spark plugs. If this maintenance information is unavailable, a good rule of thumb would be to clean them after every 10,000 kilometres of driving.
At this point, they will be likely covered in fuel, oil and debris, particularly around the electrode at the tip.
Performing this service will maximise both the car’s performance and each plug’s useful lifespan. As a result, you can drive for much longer without needing a new plug installed.

How To Clean A Spark Plug With Household Items

This cleaning task is pretty straightforward, especially using tools you already have at home. For instance, you can clean them by scrubbing, applying abrasives, or blasting them with direct heat. A gap tool would also come in handy if you have one.
For harder-to-clean plugs, you will get better results by using all three methods in conjunction.

Cleaning A Spark Plug With Sandpaper And A Wire Brush

The most straightforward way to clean any spark plug is with sandpaper (e.g. 180-grit or higher) and a brush.
With this approach, you will need to use both items to scrub any buildup in and around the electrode, the spark plug gap, and around its threads.
Besides scrubbing the outside of the plug, you will also need to scrub between sections at the tip of the spark plug. This includes the electrode, and insulator where dust and dirt accumulates.
Once everything looks clean and shiny, blow the sanded and brushed parts yourself or with a can of compressed air.

How To Clean A Spark Plug With Oven Cleaner Spray

Another household product that you may find helpful is oven cleaner spray. These sprays contain chemical abrasives that are effective for removing build-up inside gas ovens. This is similar to what you will find around the dirty spark plugs in your car.

Cleaning Spark Plugs With Butane Torch

Believe it or not, a focused blast of direct heat can also remove buildup on spark plugs. Standard butane torches are common, and they are an excellent way of burning off the build-ups that have formed. Be sure to use pliers to hold the plug so your fingers don’t get burned.
The plugs themselves are designed to withstand a lot of heat, so don’t worry about them getting damaged.

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Spark Plug Cleaning Process

No matter which approach you decide to use, here is what the process will look like:

  1. Engine Cooldown: To prevent injury, always let the engine cool down before touching it. 2-3 hours is enough, or do it first thing in the morning when the engine is as cool as it can be.
  2. Remove the spark plugs: Disconnect the spark plug wires and remove any boot in your way. Then, use a socket wrench or spark plug socket to unscrew and slide them out of the cylinder head on the engine. 
  3. Inspect: Look at the plug up close under a light to understand which parts of the spark plug need cleaning.
  4. Clean: Scrub the spark plug with sandpaper and a brush, apply oven cleaner spray, or burn off the deposits with a butane torch. For stubborn buildups, use more than one of these methods in conjunction with one another. For the space between the tip and electrode, you’ll need a gapper and a file. Slide the file in to clean any debris, then use a gapper to ensure the space is sized correctly.
  5. Reinstall: Once the plug is clean and shiny, use the spark plug socket or wrench to reinstall it in the combustion chamber. Tighten it and then reconnect its wire. Then, repeat the process with every other spark plug that you want to clean.

Frequently Asked Questions

Are Spark Plugs Worth Cleaning?

Yes, these items are still worth cleaning if you can successfully remove the buildup that forms on them.

What Can I Use To Clean Spark Plugs?

You can clean spark plugs with sandpaper and a brush. Oven cleaner spray will also be helpful as it contains abrasive chemicals. If you have a butane torch, you can use it to burn off the carbon deposits on them as well.

Can You Use WD40 To Clean Spark Plugs?

Yes, WD40 can also be helpful to loosen up some of the dirt and carbon buildup. Spray some onto a cloth and use that to apply the WD40 around your spark plugs evenly.

Can You Clean A Spark Plug With Gasoline?

Yes, gasoline has properties that make it suitable for breaking down the buildups that form on a spark plug.

What Are The Symptoms Of Bad Spark Plugs?

Whenever any spark plug goes bad, the vehicle’s fuel and air mixture will not combust efficiently. A few clear symptoms that something is wrong include: 
– The engine idles or accelerates roughly
– The engine struggles when you turn the ignition
– The engine misfires or the vehicle surges
– The engine has higher fuel consumption than normal
You can’t repair bad spark plugs, so your options are to either clean or replace them.

How Much Does It Cost To Replace A Spark Plug?

In Australia, auto spark plugs cost between $120-$150 to replace a set of four. If you prefer replacement spark plugs made of a precious metal like platinum or iridium, they will cost more at an average of $150+.