Spark Plugs 101: Everything Beginner Mechanics & Drivers Need to Know

A spark plug is what makes the combustion inside the cylinder happen… think of it as a small electric charge inside your cylinder which creates the ignition for the combustion needed to fire up your engine & keep it running.

By creating the electric charge, the spark plug ignites the air & fuel mixture that is compressed by the piston’s movement towards the top of the cylinder.

Why do we need them, you say?

Simply, without a spark plug, your engine wouldn’t start. Plus, your spark plug’s health has a lot to do with your engine’s performance (you will know there’s an issue with your spark plug when you feel that your car isn’t accelerating the best, or when you try to start your car in the winter; it struggles – which is what we call a ‘cold-start’). 

Bad plugs also lead to terrible performance, greater fuel consumption and a lower car value. A show of hands for the people that love to spend money on fuel? Crickets..

The life of a Spark Plug:

Spark plugs are made to withstand extremely high pressure and temperatures, and with time they endure thousands of kilometers in harsh conditions. That’s where the importance of the spark plug materials lies; the sturdier the material, the higher its lifetime.

As you know, every machine or mechanical part has a lifespan, and a spark plug won’t last you a lifetime.

How to find out if Spark Plugs need replacing:

You can easily sense when it’s time to change your spark plugs. Your car will literally tell you as it will directly impact your car’s performance and the sounds your engine will make.

1. It is hard to start the car if your car takes a long time to start and makes some weird noise while starting, or it just feels jerky. This means your spark plugs’ ignition isn’t timed right.
2. Poor performance: Bad timing means poor performance; you’ll know this when you feel that your car isn’t speeding up as efficiently.
3. Rattling or knocking noises from the engine: unusual noises coming from the engine because of the pistons not working properly or the combustion not happening at the right time as the spark plug misfires.
4. Higher fuel consumption for less mileage: many things may cause this to happen. However, fuel does get wasted as a spark plug isn’t giving the igniting charge at the right time.

How Often Should You Do This?

Manufacturing companies suggest that spark plugs be changed every 30,000 miles. However, a spark plug’s lifetime depends highly on its material. For example, copper plugs have the shortest lifespan, while plugs made from more durable metals such as platinum or iridium can live considerably longer and withstand worse conditions.

Keep in mind that spark plugs are inexpensive, but essential for optimal performance, so be sure to replace them within the specified maintenance window, regardless of how good the plug looks. 

Changing the Spark Plug; Time to Get Down and Dirty:

First, you’ll need the following tools:

• Torque wrench
• Socket wrench
• Spark plug socket
• Spark plug gap tool
• A rag or a brush

Now let’s start with removing the spark plugs:

1. Disconnect the battery terminals (or you can disconnect just the negative one).
2. Clean the area around the spark plugs. This way, no dirt or grime would fall into the plug pocket or inside the engine.
3. Remove the spark plug wires one at a time (the rubber insulators), you must be careful to avoid damaging the rubber boot. (The metal terminal inside the boot which connects to the spark plug must be removed simultaneously with the boot to avoid any kind of damage).
4. Remove the coil on plug (COP) by gently twisting the boot side to side while lifting up from the spark plug.
5. Take out the spark plugs one at a time by unscrewing them, make sure they’re not damaged or that there’s anything visibly wrong. (You should know that the engine fires the electric charges in a specific order and so, keep track of which wires go with which plugs – If you’re not too sure, you can always take a picture!)

1. Inspect the plugs thoroughly. You have to look for any carbon build-up because of combustion or if there was any gasoline on the plug. These signs might mean there might be bigger issues that need further checking and quite possibly repairs and maintenance.
2. Check the center electrode, if it is in the right shape, twisted, or melted.
3. If the plug looks fine, and you decide to keep it, double-check the spark plug gap and the measure on the gap measuring tool. Check your car manual for the specified gap and adjust it accordingly. When closing the gap, ensure that you DO NOT hit with a hammer or on a hard surface directly. Lightly tap it with something like a manual or a towel over a hard surface.
4. If the spark needs cleaning, do not use any metallic brushes or sandblaster. Use a regular brush (or anything that is not metallic) and a brake or carburetor cleaner, then wipe it dry.
5. If the plugs are bad or you find them to be too old, discard them and replace them with new Spark Plugs.

Installing Your New Spark Plugs:

1. Make sure each plug part number matches the part number and box description.
2. Inspect the new spark plugs for any damage.
3. Make sure the threads are clean and in the right shape, the electrode and the tip are intact, and the insulator for the plug wire is not damaged (cracked or chipped).
4. Check the gap to make sure it matches your engine’s plug gap specification (get the right gap specification from the owner’s manual; alternatively it can also be found if you google it).
5. Install the new spark plugs, while being careful not to cross-thread and damage the spark plug and cylinder head threads.
6. Be sure to tighten to the proper amount of torque using your torque wrench (check the owner’s manual or the spark plug box for the right torque).
7. Reconnect the battery.

For better performance and a better experience, replace your spark plugs regularly. You also save on fuel over the duration of time with an inexpensive fix and this will also give you a better value when you decide to cash your car.

That means more eco-friendly emissions. So you get better performance, faster acceleration, and you’ll know your car will start without a glitch.

And there you have it, all you need to know about spark plugs and how to replace them in one place. Keep up your car maintenance and keep it well in shape. Because our cars are our companions on the road and keeping them in shape will keep us alive and far from accidents.

Author: Anshed Mulla is the Managing Director of Sell Your Motors in the UAE. Sell Your Motors is a company that offers car buying services in Dubai.

For over 10 years, Sell Your Motors has been a noteworthy company in the automobile trading industry; offering professional purchasing services that reached thousands of people in the UAE.