How to Replace Your Spark Plug Wires

The best spark plugs in the world won’t deliver if the sparkplug wires connecting them to your distributor cap aren’t up to par. Good spark plug wires are essential for reliable ignition performance. Bad ones will cause spark plug misfiring, hard starting (especially during rainy, cold or snowy weather), rough idle, hesitation when accelerating, poor fuel economy and increased hydrocarbon (HC) emissions. On 1995 and newer vehicles with OBD II Onboard Diagnostics, a bad wire-prompted misfiring may set a fault code and light up your “Check Engine” signal.

Good spark plug wires are just as essential to ignition performance as your spark plugs themselves.

If you’ve got any of these problems going on with your ride, inspect the sparkplug wires and look for burns, cracked insulation, chaffing, visible arching and loose plugs or terminals. If you see any of those, it’s time for new wiring. Luckily, replacing your spark plug wires is fairly easy and typically requires no tools. But get it wrong and your hot rod won’t leave your garage until you fix it. To make sure you get it right the first time, E3 Spark Plugs offers step-by-step instructions on replacing your spark plug wires.

  • First, lay out your new spark plug wires according to length if they’re not numbered (most will be numbered and most come in black, though you’ll also find them in blue, red, orange or yellow.
  • Start at one end of the engine and remove only the first spark plug wire by pulling on the boot at the end of the wire until it pops off.
  • Follow the wire with your hand to the other end and remove it from the distributor cap. Note that in some vehicles, this end of the spark plug wire is permanently attached to the distributor cap. You know what that means – You’ll have to replace the entire distributor cap. Sorry ’bout your luck.
  • Check your spark plugs to ensure they’re still in good condition. Hopefully, you’ll see spark plugs lightly coated with grayish brown deposits. If they’re covered in black or if the electrode or core nose is worn, cracked or otherwise damaged, replace them with new spark plugs. Keep in mind that spark plugs typically foul long before they wear out and that a single fouled spark plug can ransack up to a quarter of a four cylinder engine’s power.
  • Replace the old spark plug wire with one numbered the same or of the same length. Listen for a quiet “pop” that lets you know the wire is securely connected to the spark plug. Most cars have small plastic pieces with slots designed to hold the wires in place and keep them from rubbing together or resting on engine parts. If your vehicle has one of these, use it! It will help them last longer.

DO NOT be tempted to pop off all the wires at once. Even if your spark plug wires are numbered, it’s too easy to get them mixed up and connect your spark plugs to the distributor cap in the wrong order. Do this and you’ll have changed the firing order. Your car will run like a racehorse with a bum leg or might not run at all.

Also, don’t assume that new spark plug wires will be part of your 30,000-mile tune-up. Most shops don’t include this service because it bumps up the cost of your tune up. A new set of wires can cost anywhere from $20 to more than $100 depending on the type of vehicle and the quality of the wires. Don’t skimp here. Cheap spark plug wires won’t save you a dime in the long run.