Save Money, Learn How To Replace Your Car's Sparkplugs

Save Money, Learn How To Replace Your Car's Sparkplugs

By changing your own spark plugs, you may drastically reduce the expense of auto maintenance. For a four-cylinder engine, changing spark plugs takes approximately an hour, and you can do it yourself and save at least $100 in labor costs. Most of the time, it's a straightforward task that will help to maintain optimum performance and the best gas mileage.

Tools Required

  • gap gauge
  • Needle-nose pliers
  • Rags
  • Socket/ratchet set
  • spark plug wire puller
  • swivel socket.
  • Torque wrench

Materials Required

  • Anti-seize compound
  • Dielectric grease
  • Spark plugs

Why Do Spark Plugs Need to Be Changed?

Small amounts of metal from each electrode are really burned off (eroded) when a spark leaps the distance between them. The distance between the two gradually widens until the spark is unable to jump. Misfires, poorer gas mileage, sluggish acceleration, and eventually the dreaded "Check Engine" light occur at that time.

When to Check & Change a Spark Plug

Not all spark plugs have a 100,000 mile rating. In fact, several automakers advise replacement every 30,000 miles. To determine when to change spark plugs, always refer to the owner's manual's chart of recommended spark plug service intervals. However, you can pull your spark plugs and inspect the gap and their condition if you can't recall the last time you changed them. However, after you've put in the time to start inspecting the spark plugs, you might as well replace them to provide a fresh baseline for the future.

Signs of a Bad Spark Plug

Manufacturers' recommendations for how frequently to change oil are generally unduly conservative, whereas those for changing spark plugs are typically overly optimistic. For instance, if you have 80,000 miles on a set of plugs rated for 100,000 miles, they are 80% worn and starting to affect gas mileage and engine efficiency. Even worse, spark plugs have a tendency to seize in the cylinder head after that many miles due to excessive spark plug wear. It can be expensive to remove a seized plug, especially if the cylinder head's threads are damaged. What are the advantages of replacing spark plugs then? Early replacement makes sense when you take into account the decrease in gas mileage and the potential for seized plugs.

Do it Yourself or Take it to the Mechanic?

The type of engine in your car determines the answer. To change the spark plugs on some V-6 models, parts of the intake manifold must be removed. Bring your car to a professional if you don't feel comfortable doing it. However, you can likely complete the task yourself if your engine allows for simple access to the back bank. Just be sure to use a torque wrench and space the spark plugs correctly. The tools displayed are offered by online vendors and car parts retailers. Ask the shop assistant for your vehicle's spark plug gap and torque specs while you're there. Likewise, get a tiny packet of dielectric grease. Prior to scheduling an appointment, it's crucial to inquire about the cost of spark plug replacement.

How to replace your own sparkplugs

Open Up and Clean Your Work Area

Start by removing the plastic “vanity” cover (if equipped) and the air cleaner assembly from the top of the engine.

  • Label any vacuum hoses you remove so you restore them to the right place.
  • Blast compressed air around the ignition coils to prevent crud from falling into the cylinders. Then blow any remaining loose dirt off the engine before you set out your tools and new plugs.

Remove the Ignition Coil and/or Boot

  • Disconnect the ignition coil electrical connector by depressing (or pulling up) on the locking tab.
  • Rock the connector off the coil.
  • Remove the coil hold-down bolt and pull out the entire coil and boot assembly.

If your car doesn't have COP ignition, the spark plug wire will end in a boot that attaches to the spark plug. A spark plug wire puller makes it easy to pull the boot off.

Unscrew the Plug

  • Blow away the dirt and grime that’s settled on and around the plug since it was installed.
  • Slide the proper size spark plug socket over the plug.
  • Rotate the plug counter-clockwise to loosen it.

How To Gap a Spark Plug

Gap all plugs before installation using the manufacturer's specs. Always check the spark plug gap before installing it.

  • Slide the correct wire gauge (or gap gauge) between the electrodes. The wire should drag slightly between them.
  • If the gap is too small, open it with the gap gauge by prying up.
  • If the gap is too large, tap the side electrode lightly on a solid surface.
  • Place a small dab of anti-seize compound on the plug threads and hand thread the plug into the cylinder head.

Install the New Plug

Proper spark plug torque is critical in today's engines.

  • Always use a torque wrench and the manufacturer's spark plug torque specs. Insufficient torque can result in a plug blowing right out of the cylinder head, taking the threads with it. Too much torque distorts the plug.
  • If you used anti-seize compound on the plug threads, reduce torque by 10 percent. If you don’t have a torque wrench, go to the spark plug manufacturer’s website to find manual tightening techniques and spark plug torque specs.

Lube the Spark Plug Boot and Button It Up

  • Apply a thin coating of dielectric grease around the inside of the spark plug boot before reinstalling the coil. The grease prevents misfires and makes it easier to remove the boot in the future.
  • Reinstall the ignition coil, hold-down bolt and coil electrical connector.
  • Reinstall the air cleaner and vanity cover and fire it up.