How To Change Spark Plugs

What’s a relationship with no spark?

byTony Markovich|
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Like rotating tires or changing oil, replacing spark plugs is a job that can be easily, and inexpensively, done in the confines of your own home. Although they don’t need maintenance as often as the other two tasks, spark plugs are equally as important and require consistent monitoring.

Although it might seem intimidating to begin removing engine parts, novices need not worry. With the right tools, and help from your favorite informational team (wink, wink), spark plugs are essentially plug-and-play. 

To keep the wrenching as stress-free and smooth as possible, The Drive’s crack informational team has laid out exactly what you need and what to do when you want to change your spark plugs. 

Spark Plug Basics

Estimated Time Needed: Half-hour to 3 hours, depending on plug location

Skill Level: Beginner

Vehicle System: Engine

What Is a Spark Plug?

A spark plug is a key cog in a vehicle’s ignition system. The small insulated device uses high-voltage electricity to create a tiny spark within a cylinder combustion chamber. The spark, which is created between a center electrode and a ground electrode, then ignites the air and fuel mixture inside the cylinder, and poof, you’ve got ignition.

Spark plugs are made with a variety of different materials. The most common types use copper, nickel, iridium, and platinum, to varying degrees. Ceramics are used as insulators and protectants on spark plugs.

The composition of NGK spark plugs., NGK

Spark Plug Replacement Safety

Working on your car can be dangerous and messy, so here’s exactly what you’ll need to ensure you don’t die, get maimed, or lose a finger.

Most importantly, spark plug replacement needs to be done with the car off and cooled down completely. 

Everything You’ll Need To Change Spark Plugs

We’re not psychic, nor are we snooping through your toolbox or garage, so here’s exactly what you’ll need to get the job done. 

Tool List

Parts List

  • A set of spark plugs with anti-seize properties (thus, anti-seize lube is not needed)

Organizing your tools and gear to change your spark plugs so everything is easily reachable will save precious minutes waiting for your handy-dandy child or four-legged helper to bring you the sandpaper or blowtorch. (You won't need a blowtorch for this job. Please don’t have your kid hand you a blowtorch—Ed.)

You’ll also need a flat workspace, such as a garage floor, driveway, or street parking that’s also well-ventilated to change your spark plugs. Check your local laws to make sure you’re not violating any codes when using the street because we aren’t getting your ride out of the clink.

A socket wrench and used spark plugs., DepositPhotos

Here’s How To Change Spark Plugs

Let’s do this! 

Removing the Spark Plugs

  1. Disconnect the negative battery terminal. 
  2. Remove any covers, if necessary.
  3. Vacuum, blow out, and clean the area around the spark plugs to prevent dirt and grime from falling into the spark plug pocket or the engine.
  4. Remove the spark plug boots one at a time. The engine fires in a specific order, and it’s paramount to retain that order, so as you go, use a labeling method such as masking tape to mark which wires go to which plugs. 
  5. Remove the spark plugs one at a time and inspect for damage, build-up, or foreign materials.

Inspecting the Spark Plugs

  1. All spark plugs will be slightly darkened with black or brown coloring as part of normal wear, but look for carbon build-up, oil, or gasoline on the plug. If any of these are present, bigger issues that need further diagnosing could be the causes.
  2. Check the center electrode. If it is still relatively even and correctly shaped, it might not need replacing. (However, spark plugs are inexpensive and vital to a car’s health, so be sure to replace them within the specified maintenance window, regardless of how the plug looks). 
  3. If the plug is young, and you decide to keep it, check the spark plug gap with the gap measuring tool. Check the manual for the specified gap and adjust the gap. When closing the gap, do not hit with a hammer or on a directly hard surface. Lightly tap on something like a manual or on a towel over a hard surface.
  4. If you’d like to clean the spark plug of dirt, lightly rub with a non-metallic brush, spray it with brake or carburetor cleaner, and wipe dry. Do not use a sandblaster. 
  5. If the plugs are bad or too old, throw them out and replace them with new plugs.

Installing New Spark Plugs

  1. Most modern spark plugs come with a preset gap from the factory, but it never hurts to do a double-check and adjustment with the gap tool.
  2. Using a plug starter or the socket extension (spark plug sockets typically have magnets or rubber boots to hold the spark plug), hand-thread the new plugs back into the engine. If it feels difficult, pull it back out and try again. The last thing you want to do is cross-thread the plug or over-torque.
  3. Look up the torque specification for your vehicle and use a torque wrench to tighten the spark plugs.
  4. Reattach the plug boots to their specified plug mates.
  5. Reconnect the battery.

That’s it, well done!

Spark plug wires for four spark plugs., DepositPhotos

Get Help With Spark Plugs From a Mechanic On JustAnswer

The Drive recognizes that while our How-To guides are detailed and easily followed, a rusty bolt, an engine component not in the correct position, or oil leaking everywhere can derail a project. That’s why we’ve partnered with JustAnswer, which connects you to certified mechanics around the globe, to get you through even the toughest jobs. 

So if you have a question or are stuck, click here and talk to a mechanic near you.

Possible Symptoms of Faulty Spark Plugs

Here are some of the most common symptoms of faulty spark plugs.

  1. The car has trouble starting.
  2. A knocking or pinging sound is coming from the engine.
  3. The car has a rough idle.
  4. Performance is muted or inconsistent.
  5. Noticeable fuel economy degradation. 

How Often Do You Need To Change Spark Plugs?

On average, spark plugs should be changed every 30,000 miles, but that could fall between 20,000-40,000 depending on the vehicle. Read the owner’s manual for specific information about your car, and use your judgment when checking the plugs to determine if they need to be replaced. If the plugs are corroded, it’s time to change.

How Much Does It Cost To Change Spark Plugs?

On traditional consumer cars, not performance-oriented racecars, an average single spark plug can range from $2-$20. 

Pro Tips To Change Spark Plugs

We spoke to Senior Product Manager of Bosch Spark Plugs Justin Wolf about what a beginner needs to know before tackling the task of changing spark plugs. Here are his top tips for DIYers: 

  • "The most important thing to remember is to always follow the vehicle manufacturer’s instructions for replacement. This is a blueprint on how to best repair your vehicle."
  • "Before you begin, ensure the engine has cooled for your safety." 
  • "Complete one cylinder at a time to avoid mixing coils or spark plug wires."
  • "Avoid downgrading in metallurgy – if your car came with an Iridium plug, avoid a platinum or copper replacement. 
  • "You can damage the electrodes or ceramic by mishandling the spark plug. Take your time and avoid rushing the repair to achieve the best results."
  • "The most common mistake people make is overtorquing or overtightening spark plugs."

Life Hacks To Change Spark Plugs

Since you may not have access to the right tools or a friend with that wrench you need, we also compiled a list of our best hacks to make your life easier and drain your pocket less.

  • If you don’t have a plug starter or a socket that grips or holds the plug, a spare rubber hose can be used, if it’s the right size to grip the plug.
  • Long-nose pliers can also work, provided you make sure you don’t damage the spark plug’s top when putting them in.
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