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How To Clean Spark Plugs (Step-By-Step Guide) + 4 FAQs

December 8, 2021

A car spark plug needs to be cleaned once it accumulates a lot of grime and oil. 

If it isn’t cleaned, you may face a range of troubles, including slow acceleration, lousy fuel economy, deposits on the cylinder head, etc.

But how do you clean them? 
Or should you just get a new plug?

These are the questions we’ll answer today!

This step-by-step guide will show you how to clean spark plugs and we’ll also answer a bunch of relevant FAQs to help you understand the process better.

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Let’s begin!

How To Clean Spark Plugs? (Step-By-Step)

Before we jump into a step-by-step guide on how to clean spark plugs, let’s go through all the equipment and materials you’ll need:

Apart from gathering the equipment, you must perform 3 important preparation steps before cleaning spark plugs. 

Now that you have everything you need and all prepared, let’s discuss the 2 ways of cleaning spark plugs:

Method 1: Clean With Abrasives

Here’s the first method for cleaning spark plugs:

Step 1: Detach The Spark Plug Wire And Unscrew The Plug

The best way to remember where each spark plug wire goes and to stop debris from falling into the cylinders or combustion chamber is to clean each dirty spark plug, one at a time.

Hold the spark plug wire (or ignition coil) securely, very close to the spark plug, and pull it away off the plug.

Don’t yank it or pull from high on the wire. 
If you do, it could sever the inside of the spark plug wire from its connector.

If you can’t seem to remove the spark plug wire, twist it a bit to loosen it and then pull.

Once done, remove the plug using a spark plug socket. Turn it in a counter-clockwise manner to unscrew the plug till it’s loose. Then you can unscrew it by hand.

Step 2: Use 220-Grit Sandpaper On The Spark Plug Electrode

Once you’ve removed the spark plug, look at the firing end (or firing tip). This is the side that fits into the engine. There you’ll find a small piece of metal extending out of the spark plug, known as the electrode. 

If this electrode is black, discolored, or doesn’t look like bare metal, use sandpaper to clean it. Move the sandpaper back and forth on the spark plug electrode till you see the clean metal.

While checking the spark plug electrode, also check the ceramic insulator for damage or dirt buildup.

Note: Always use protective eyewear and a mask when using sandpaper.

Step 3 (Optional): File Down The Dirt On The Electrode

If the spark plug electrode is extremely dirty and the sandpaper doesn’t work, it’s time for a new spark plug. 

But in case of an emergency, you can use a small file to remove the carbon buildup on the electrode.

Step 4: Scrub The Threads With A Wire Brush

It’s possible to have oil and dirt build-up in the spark plug threads. 
If that’s the case, it’ll be difficult to re-install them. 

Clean it by scrubbing the threads with a wire brush. 

First, clean it by holding the wire brush at an angle to move in the same direction as the threads. This’ll help remove the most dirt off the fouled spark plug. Once done, scrub from other angles for ultimate spark plug cleaning. 

Note: Wear gloves when scrubbing with a wire brush to prevent poking yourself with it.

Step 5: Spray Brake Cleaner On The Spark Plug

Brake cleaner can clean many car parts — one of them being spark plugs.

Spray the brake cleaner on the plug, including threads. Then wipe it off with a clean cloth to remove any remaining gunk.

If need be, you can use the brake cleaner and wire brush collectively to deal with stubborn filth.

Then wipe thoroughly with the clean cloth to remove every bit of the brake cleaner that soaked up the grease and grime.

Step 6: Reinstall The Clean Plug And Repeat The Process For The Remaining Plugs

Now that you have a clean spark plug, place it back and reconnect the ignition coil or spark plug wire. Then repeat the entire spark plug cleaning process with each fouled spark plug and reinstall them.

To reinstall a clean spark plug:

There’s another way of cleaning spark plugs as well. 
Let’s check it out.

Method 2: Using A Blowtorch

Here’s how to clean spark plugs using a blowtorch:

Step 1: Hold The Spark Plug With Pliers

You’ll need to hold the spark plug with pliers to protect your hands from heat produced by the blowtorch. This is an essential safety measure, so you must take it seriously. 

Don’t hold it too tight with the pliers, or you’ll damage the spark plug. Just let the plug sit in the pliers like a handle extension.

Step 2: Use Gloves And Turn On The Torch

Turn the knob on your propane torch, which lets the gas flow, and then hit the ignition button. The propane torch will then light up.

Step 3: Hold The Spark Plug In The Flame

The flames from the propane torch will burn the carbon buildup and dirt stuck on the fouled spark plug. 

Rotate the spark plug side to side as you hold it in the flame till the electrode and the end of the plug turn red hot.

Step 4: Let The Spark Plug Cool

Since the plug is now extremely hot, let it cool for some time. Once it has cooled entirely, you’ll have a clean spark plug ready for reinstallation.

Warning: The spark plug will turn from red hot to its normal color long before it has cooled enough to be able to touch.

Step 5: Repeat The Process For Each Dirty Spark Plug

After the clean plug has cooled down, reinstall it and reconnect the spark plug wire (or ignition coil). Then repeat the entire process for each dirty spark plug one by one.

Now, you probably have a few more concerns and queries. Let’s answer some of them.

4 FAQs About How To Clean Spark Plugs

Here are answers to some common questions over how to clean spark plugs:

1. Can I Clean An Old Spark Plug?

Yes, you can clean an old, fouled plug. 

However, it’s best to replace it with a new plug in most cases. That’s because an old spark plug won’t give the optimal performance like a new spark plug will. 

After all, electricity discharges best from sharp edges that only a new plug can have. 
And a used, old plug will have worn edges.

Moreover, the spark plug cleaning process can contribute to the wearing of the edges.

2. When Do I Need A New Spark Plug?

To understand if you have a fouled plug and need to replace it with a new plug, look for certain signs such as:

3. Can I Spray Carb Cleaner Inside The Spark Plug Hole?

Yes, you can spray carb cleaner, short for carburetor cleaner, inside the spark plug hole. 

This’ll help dissolve hardened debris and loose materials in the spark plug wells. After that, you can remove the filth with a compressed air can.

4. How To Set The Spark Plug Gap?

To do so, you’ll need a spark plug gap tool. Use it to correct the gap between the plug and electrode. 

Check the owner’s manual to find the accurate spark plug gap measure. 

Then pry the electrode further from or closer to the plug’s body to increase or decrease the gap. Do this until the spark plug gap meets the car’s specifications.

Final Thoughts

Spark plug fouling can occur after 20,000 to 30,000 miles.

And it doesn’t matter if you wish to clean or replace an old plug, it has to be done right because spark plug fouling can cause severe car issues. 

Any debris in the spark plug hole or combustion chamber due to cleaning can damage the engine. And the car spark plug installation needs to be accurate with the right amount of tightness.

If you need help, you can always rely on a professional mechanic, like Repairsmith. We’re a mobile auto repair and maintenance solution available for you 7 days a week. We also offer competitive and upfront pricing on a range of car services and repairs.

Contact RepairSmith today, and our ASE-certified technicians will clean your dirty spark plug or replace it, right in your garage, in a jiffy.