How to Clean Car Engine Spark Plugs


Spark plugs are crucial parts of an engine, igniting the fuel-air mixture that powers your car. They’re constantly in use, which means that, over time, they can accumulate oily or carbonaceous deposits. These can impact performance, so from time to time, spark plugs need to be cleaned. 

Your mechanic will be able to perform this for you, but if you feel confident with automotive DIY, it’s not too difficult a task to do at home. Here’s how.

You will need:

  • A spark plug socket
  • Rags
  • 220-grit sandpaper
  • Lightly abrasive file
  • Wire brushes
  • Brake cleaner
  • Gap tool
  • Socket wrench

How to remove the spark plug

  1. Disconnect the negative battery terminal and ensure the cable cannot accidentally contact the terminal.
  2. Find the spark plugs. Look for cables running into the top of the engine – the spark plugs are beneath each of these cables.
  3. Clean the area around the bottom of each cable with compressed air – no debris should be present when you remove the spark plug.
  4. Label each spark plug (and its corresponding cylinder) with masking tape so you do not confuse them – they’re not interchangeable!
  5. Firmly hold the boot that the wire is plugged into and remove the spark plug wire. Remove and clean each one at a time, to reduce the risk of debris entering the cylinders.
  6. Using the spark plug socket, remove the plug from within the cylinder.

How to clean the spark plug

  1. Take your sandpaper and lightly brush the curled electrode on the end of the plug until you it is clean, and you can see bare metal.
    • If the electrode is especially dirty, use a file to remove the dirt.
  2. Using one or two wire brushes (depending on how oily the plugs are), remove any grime from the spark plug threads until they are clean – a small amount of oil is fine, but the majority should be removed.
  3. Take the can of brake cleaner and spray the spark plug, using your rag to wipe away any dirt.
  4. Placing the gap tool between the electrode and spark plug body, press or force apart the electrode to the exact measurement as noted in your vehicle’s service manual.

How to reinsert the spark plug

  1. Place the spark plug into the spark plug socket so the threads are exposed.
  2. Put the plug inside the correct cylinder, making sure the threads are correctly lined up, then lightly screen in the plug until it is secure. 
  3. Use your socket wrench to tighten the spark plug – but be careful not to overtighten as this can damage the plug.

Repeat the steps above for each spark plug in the engine, making sure not to put the incorrect plugs in each cylinder.

How often should you replace spark plugs?

The service life of spark plugs can vary hugely depending on the vehicle model and quality of the spark plug. Single-electrode copper-nickel plugs can last 25,000 miles, while higher-specification, multi-electrode iridium, and platinum plugs may last up to 120,000 miles. With spark plugs, paying for a higher quality model really can cut down on maintenance.

Cleaning your car engine’s spark plugs isn’t too complex a task, but as always, if you don’t feel confident, we always recommend visiting your local mechanic instead.


Leave A Reply