How to Gap Spark Plugs

Most new car parts are plug-and-play. You simply remove the old part, replace it with the new one, tighten some … Continued

Most new car parts are plug-and-play. You simply remove the old part, replace it with the new one, tighten some screws, and you’re off on your merry way. Spark plugs aren’t that simple.

Spark plugs are hugely important to your car’s performance and correctly installing them requires properly gapping them, something that’s become sort of a lost art. Luckily, you have Car Bible’s editors to dust off the long-forgotten manuals and get you gapping spark plugs like you were born for it.

What Is Gapping a Spark Plug?

Gapping a spark plug is when you adjust the gap between the spark plug’s center electrode and ground electrode.

Gapping a spark plug involves a spark plug gap tool, a coin-like metal device that’s tapered around its circumference. Another version looks like a color swatch you’d get at the hardware store and are of different thicknesses.

The taper is marked by thickness, which you use to gap your spark plugs.

Mechanic removing spark plug from car

How To Gap Spark Plugs Guide

We know that the idea of gapping a spark plug may be intimidating, but it doesn’t have to be. Here’s exactly how to gap spark plugs.

  • Gapping the Spark Plug
  1. Determine your car’s required spark plug gap. This can be found either in your car’s manual or online.
  2. Take one spark plug and insert the spark plug gap tool between the center and ground electrodes.
  3. You may have to increase the gap, which you’ll do by sliding the tool between the two electrodes. Or you’ll have to decrease the gap by gently, but firmly, squeezing the electrodes together.
  4. Check the gap again to ensure it’s correct.
  5. You’re done!

Also, besides gapping, spark plugs need changing too, once in a while. Sadly they are not everlasting. We are sure that our seasoned readers already know how to do it, but for you newbies here, we also have a handy guide on how to replace spark plugs  efficiently and safely. So, if you ever need a handy reminder on replacing spark plugs – no worries we got you covered. Better be safe than sorry, we always say.

Spark plugs with a good gap

Spark Plug Gap FAQs

Q: Why Do You Need To Gap a Spark Plug?

A: You need to gap your spark plugs to ensure your car’s ignition stays consistent throughout its combustion cycle. A precise air and fuel mixture requires a precise and timely spark to burn it. If you don’t, you’re liable to damage your engine’s components.

Q: What Are Spark Plugs Made Of?

A: Spark plugs are made with different materials. Common types use copper, nickel, iridium, and platinum. Ceramic is used as insulators and protectants on spark plugs.

Q: What Happens If You Don’t Gap Spark Plugs?

A: If you don’t gap your spark plugs or gap them incorrectly, the gap may be too wide for a spark to ignite, it could skip the spark entirely, or it could ignite the fuel/air mixture too soon causing a rough idle or misfire.

Q: What Happens If Your Spark Plug Gaps Are Too Small?

A: If your spark plug gap is too small, the spark may be too weak to ignite the fuel/air mixture to cause ignition. The result is an engine that will run inefficiently or rough.

Q: Do Spark Plugs Come Pre-Gapped?

A: Some do! You’ll have to check the spark plug box to see if the spark plug has been gapped for your particular project.

Spark Plug Gap Tips & Tricks

There are always tips and tricks to learn, and Car Bible’s editors want to give you all theirs. Here are our tips and tricks for gapping a spark plug.

  • You can clean the spark plug of dirt by lightly rubbing it with a non-metallic brush, spray it with brake or carburetor cleaner, and wipe dry.
  • Long-nose pliers can also be used to increase the gap between the electrodes, provided you make sure you don’t damage the spark plug.
  • A lot of issues with your engine and ignition can be avoided if you know how to read the warning signs that your spark plug is telling you. You don’t know what we are talking about? Then check out our How to Read a Spark Plug guide right now.

And remember – drive safely and good luck with plugging.

Jonathon Klein

Jonathon KleinJonathon has jumped Aston Martins for Automobile Magazine, clocked 200 mph in a McLaren 720S for Playboy, and sampled his best life behind the wheel of a Ferrari Dino Evo for Road & Track. He’s hopelessly addicted to the strongest coffee he can brew. Please send him more. Contact the author here.