• Likes:
    • Views:
  • Last Updated: 21 April 2020

Before we’ll clarify how to change spark plugs, let’s jump deeper into a definition and their essence. They are the spare parts of the car or other vehicles for fuel-air mixture ignition in the petrol engine in the various types of an ignition system. They have a direct impact on the engine’s operating. They provide the vehicle’s start quality, maximum speed and optimal fuel consumption, stability at idle and other functions. Why change spark plugs? New parts provide the correct engine’s work, emission reduction, and good motor dynamics. They help regulate thermal loads and severe mechanical stresses, as well as to make the cylinder’s working life longer.


Changing spark plugs is required after its long-term work. They’re always under extreme voltage up to 60.000 V and extremely high temperatures in the combustion chamber that leads to their electrodes’ outburning and clearances’ increasing going out the factory parameters. The spark’s depreciation is the reason for uneven engine’s performance. The frequency of their replacement depends on their types. For example, iridium sparks have a longer working life than common ones. The average period of service for all those spare parts is up to 16.000 miles of the run.


Spark plug replacement needs some tools.

  • If you have high voltage wires, we recommend using special boot puller plier with isolation to remove points.
  • Tongs for demounting ignition coils.
  • Reamer holder and a handle for unscrewing. In the case of lacking either reamer holder or a handle, take the extension socket and adapter.
  • Standard 5/8″ or 13/16″ socket or an advanced socket with an add-on wobble extension.
  • To unscrew the spark, pick up proper multi-sided sockets for keys (14mm, 16 mm or 20.8 mm). You can use a socket with magnets, a spring unit or a piece of rubber to hold the spark in the head.
  • Wrench to measure the clearance.
  • Torque wrench to tighten the spark plugs.


Not only tools needed to change spark plugs but some additional materials and accessories.

  • Wire loom spacers to avoid misfires and to preserve gas mileage, ignition coil and module, and, sometimes, the powertrain control module.
  • Anti-seize to escape permanent plugs’ connection with the cylinder head threads.
  • Dielectric grease to make boot removal easy without voltage leaking out.
  • A can of compressed air to remove small particles of dust.

We recommend replacing the distributor cap as well, that let the ignition system perform at maximum efficiency.


Let’s deal with some general information on how to replace spark plugs. First, choose the new parts with the shape that is identical to the previous ones. Then, consider the heat rating that is recommended in the logbook after the car service. Start working with the cool engine to avoid burns. Preliminary stage:

  • Find where are spark plugs located.
  • Prepare all the necessary tools and materials.
  • Clean the engine to remove dust, use a can of compressed air to make the process easier.

Main stage:

  • Remove the old parts.
  • Install the new ones.
  • Mount the high voltage wires that you’ve removed before.


How to understand when to change spark plugs? The visual examination is crucial to reveal the possible damages. For example, if the plug is wet and has residue, the replacement is necessary. Sometimes, there are cracks in the ceramic insulator or brown annuluses around the electrodes that imply the immediate replacement. The increased clearance between electrodes is one more warning sign. However, some problems that appear while driving may also mean the spark plugs further unsuitable.

  • The starter doesn’t work on the first try.
  • The fuel consumption is increasing.
  • The car performance is decreasing.
  • Muffled slams in both pulsating air and pulsation systems.


How often to change spark plugs? This was subject to the type of this spare part and on the ignition system. For example, most of the advanced engines use lean fuel composition that reduces the plug’s length of service to 10.000 miles. The individual driving manner, engine attrition, and low-quality fuel also contribute to their working life reduction. The parts made of the rare-earth metals work much longer because they’re more credible and resilient to dust. It deals with iridium, golden, silver, and platinum items. Some manufacturers also enhance electrodes to make the parts serve longer. They increase the number of side electrodes or make special V or U-shaped nicks on them. So, choose innovative and high-quality spark plugs to make them serve as long as possible.


The majority of the advanced cars have overwhelming construction that requires demounting almost half of a motor to reach the spark plugs. Computer diagnostics equipment is necessary to check the ignition system. So, we recommend applying for a pro if you lack the experience and tools for a proper spark plug replacement. However, the trial is possible if you’re sure about your powers.


1. Make Your Workplace Clear as Your Dining Table

The spark plug service starts from the preparation if workspace. Provide enough space on the desk or even of the floor to place there the necessary tools and materials in order not getting all mixed up.

2. Demount the Ignition Coil/Boot

Switch off the engine and open up the hood to find out the ignition coil. Its possible placements are next to the fender, starter or ignition distributor. We recommend following the wires from the ignition distributor in the opposite direction from the spark plugs. Use goggles and tools with the isolated handles to avoid electrocution.

3. Wire Puller as a Silent Assistant

When the ignition component fails, it should be replaced, but removing the sparks and its wires can be a challenge. Wire puller is helpful in disconnecting the boot or a coil from the distributor or coil to provide the hassle-free spark plugs and wires unfastening. This tool is very straightforward and even a rookie can handle it. It is usually made of durable materials to succeed even with heavy-duty parts and provide for its owner long-lasting service. When choosing the right model, pay attention to its toughness, type of drawing block hookup, and length of a puller. Such characteristics as maximum die-pull, reduction area, and wire tensile strength are also important. Wire pullers fit spark plug wire boots to avoid damaging spark plug wires. It is a professional tool with a gripping looped end that allows the user twisting the boot on the spark plug, breaking the corrosion or plain tight grip, so that the boot can be pulled free without crushing the boot top. We’d recommend buying a tool with no less than 11 inches in length.

Some Tips on Pulling the Booth

How to manage the boot wires? Take the caps of the wires first. They usually sit very tightly that’s why it is better to shake them a little from the right to the left, and only then to pull them up to the moment of disconnecting between the wire and the plug. Take the wire off only one plug because they are hooked up with the unique connectors that are not allowed mixing up. Remove the wire from 1 plug at a time, and don’t disconnect both ends of it!


Take a soft (not synthetic) and clean piece of textile or a little paintbrush to remove dust from the area where the spark enters the block. A soda straw may also come in handy to blow all the dirt away. Keep an eye the hole into the cylinder to prevent it from being polluted with junk while demounting the plug. The next step is to place a large spark plug socket with the rubber lining (magnets or a spring unit) over the old spark plug. Add some pressure (not too much without flip throws) while turning it slightly to be convinced that it’s all the way down. Some rational strength is necessary but try to control your enthusiasm. The mistake will cause damages that will cost you money.

Swivel Socket and Bent Ratchet

To make the procedure easy and fruitful, use such straightforward tools as a swivel socket set and bent handle ratchet. Fortunately, the modern auto market offers a wide range of them from bare-bones entry level to professional grade. A handle ratchet snaps into one end of a socket via a square-drive connector. The other end of the socket is put on a fastener. A ratchet mechanism allows engaging and tightening a fastener when swinging it in a clockwise direction, as well as loosening fasteners. The main task is to suit a ratchet and socket in the best way that’s why to choose the right socket size for spark plug’s replacement.


Some new items are pre-gaped but we recommend calibrating the gap to make it corresponded to a certain car. This is crucial for those who prefer to buy on the Web. In that case, the spare part may be mishandled or dropped during packaging or shipping. If you have no idea about your perfect gap, apply for the manual or official dealer before the spark plug’s replacement. However, we can define the pattern. The engines with high compression and power require small gaps.


  • Prepare a special gauge to verify the gap.
  • Select the right wire considering the dimension of the gap.
  • Run the wire between 2 electrodes and make it cover them as it passes through.
  • Expand the gap, if it is not wide enough, by hooking the gauge on the ground electrode and pulling gradually. Follow the procedure to prevent the gauge from contacting the porcelain or the center electrode. It can touch only the ground electrode!
  • Sometimes, narrowing the gap is required. This step needs pressing or tapping the ground electrode smoothly against a soft surface.
  • Make the final check and adjustment.

A well-gapped plug never skips or misses at high speeds, makes cylinder drag or lets he engine to start rattling.


Gap gauge/feeler is a very simple measurement system that comes in straight leaf or tapered leaf modification. The first variant is suitable for spark plugs while the latter usually measures gaps between electrical contacts, shafts or bearings. We recommend choosing models with corrosion-resistant finish and heat treated for toughness. Despite the brand and quality, they are not expensive to replace if you lose or bend them.


When you’ve already pulled the old spark plugs out, don’t forget to examine it, eliminate dust and particles, and gap it to male perfect adjustments if it is necessary. Then install the new item before you’ll start removing another old one. To make everything correct, use the optimal amount of torque. The needed torque depends on plug thread diameter. If the thread diameter is 18 mm, the proper amount of torque is 35 to 40N·m (3.5 to 4.0 kgm ). The spark plug torque wrench can be very helpful for this purpose because it prevents the common over-tightening problem. However, you should adjust it considering the brand listed setting. This tool fits to tighten fasteners but don’t forget to dial the wrench back to zero (never below it).


While trying to diagnose ignition coils unseating, one more question raises. Is it necessary to use anti-seize lube or grease on the currently installed spark plugs? High-quality products are able to prevent galling and seizure. Sometimes, the substance is applied to the shaft of the coil to prevent spark jump, as well as moisture from entering the spark plug wire end. Don’t use too much of the material for the same area and never apply it to low voltage plug-in connectors. Do you have experience of installing spark plugs from scratch? Share your achievements, impressions, and conclusions in the comments.

Share your thoghts
Please fill required fields
Please fill required fields
Please fill required fields