Spark Plugs

What is a spark plug?

spark plug
This website contains some great close-up photos of a spark plug firing.

Every gasoline uses a spark plug to ignite the air/fuel mixture in each cylinder. Very high electrical voltage generated by the ignition coil is fed into the spark plug, and then – having nowhere to go – is forced to ionize (or jump) the gap between the spark plug’s two electrodes. This creates a spark that ignites that gasoline in the cylinder, causing the fuel to burn. 

This process happens dozens of times every second. Over its life, the average spark plug in a modern vehicle will fire over 250 million times!

airdrie spark plug
Electricity passes through the centre of the spark plug; crosses the gap; and returns to ground through the threaded body.

Why do spark plugs have to be replaced?

Comparison of a very worn-out spark plug vs a new one. Notice the centre electrode is totally worn away!

Every time a spark plug fires, a microscopic amount of material is eroded from its electrodes, which causes the electrodes to slowly wear down. This causes the gap between the electrodes to increase in size. As the spark plug gap grows, more power is required from the ignition coil to create a spark strong enough to cross that gap. Eventually the coil just can’t supply this much voltage, and the spark plug stops firing. This causes the engine to misfire, or run poorly.

Even before the engine reaches the point of misfiring, worn spark plugs are already starting to take their toll on your engine’s performance and fuel economy. This is because your ignition coil can only produce so much voltage. The more voltage that’s required to ionize a worn spark plug gap, the less voltage is left to keep the spark “burning” for a set amount of time. 

Along with wearing out, spark plugs can also become fouled, where deposits left behind from burning fuel and oil build up on the spark plug. This can also cause the spark plug not to fire correctly. 

When do spark plugs have to be replaced?

How often should spark plugs be changed? Most modern vehicles require new spark plugs every 100,000 – 180,000 km. You can find your vehicle manufacturer’s recommendations inside the maintenance section of your owner’s manual. Don’t have an owner’s manual? We’d be happy to look up this information for you.

Platinum? Iridium? Explaining spark plug construction:

airdrie tune ups

Twenty years ago, almost every spark plug used a steel ground electrode with a copper centre electrode. This design still works very well today, but these spark plugs wear out quickly and require fairly regular replacement: usually every 40,000 – 90,000 km. Today’s vehicles are required by law to maintain like-new emissions and fuel economy levels for a long time, which has created the need for a longer-lasting spark plug. 

Because of this, today’s vehicles use a spark plug whose electrodes have a tip made of various precious metals, including platinum; palladium; or iridium. These metals erode away much more slowly, which means the spark plug gap wears (or grows) very little over time. These metals also allow for a finer or smaller electrode tip, which resists deposit build-up and fouling. 

Do platinum or iridium spark plugs improve performance or economy?

Contrary to popular belief, these precious metal spark plugs are not designed to increase performance. They do not produce a “stronger” or “hotter” spark. (The firing voltage of a spark plug is a function of the gap size; the pressure inside the cylinder, and – to some degree – the output of the ignition coil.)

The only advantage of a precious metal spark plug is that it resists fouling longer, and wears out more slowly; they won’t improve performance. The best spark plug for your vehicle is the one that the rest of your engine was designed around: the original spark plug.

Selecting the right replacement spark plug:

airdrie spark plug replacement

With all the different spark plugs out there, selecting the right spark plug for your vehicle can sometimes be tough! Unfortunately, even some Airdrie automotive repair shops don’t get this right; unknowingly doing their customers a disservice by installing spark plugs that aren’t quite correct for their vehicle.

As an example, let’s look at a 2012 Honda Civic. The OEM (factory) spark plug for this vehicle is a double platinum design, as shown in this photo. This means it uses a platinum-tipped centre electrode and ground electrode, and these spark plugs are designed to last for 160,000 km. A popular aftermarket replacement, the NGK G-Power, is technically also a platinum finewire spark plug; but it only has a platinum centre electrode and is designed to last for only 60,000 km!

To ensure that we provide a lasting and correct service to our customers, we only use genuine OEM spark plugs in every vehicle.

What about those fancy spark plugs I’ve seen advertised? (E3, Platinum Plus 4, etc.)

e3 spark plugs airdrie
The only difference you’ll notice from these fancy spark plugs is less money in your bank account.

For decades now, companies have popped up offering “revolutionary” new spark plug designs that claim to provide major improvements in horsepower or fuel economy. This simply isn’t possible, and these spark plugs are a waste of money. 

In today’s competitive marketplace, if there was a horsepower or efficiency improvement to be had by changing spark plug design, car manufacturers would have done this years ago. 

In some vehicles, using these radical spark plugs actually results in a loss of performance, or even a misfiring/rough running engine.

What is a carbon tracked spark plug?

airdrie engine repairs
Two spark plugs that are carbon tracked because of deteriorated spark plug wires.

Carbon tracking refers to the black line that is burned into a spark plug when, instead of taking its normal path through the inside of the spark plug, electricity arcs down the side of the ceramic insulator on the outside. Since the spark plug fires thousands of times per minute, this quickly burns a “track” into the spark plug. Since the spark is no longer going through the electrodes, the spark plug does not fire and the engine runs poorly as a result.

What should you do when you see a carbon tracked spark plug? This problem is not actually due to a failure of the spark plug; it’s due to the breakdown of the spark plug wire (or ignition coil boot) that seals to the ceramic insulator. If only the spark plug is replaced, the new spark plug will eventually carbon track again in the same place. For a lasting repair, the spark plug and ignition wires or coil boots must be replaced.

What is a fouled spark plug?

airdrie engine diagnosis
Bad oil fouling on a spark plug.

Fouling refers to the build-up of deposits from the burning of gasoline or oil on the spark plug. This will also cause the spark plug not to fire correctly, creating an engine misfire. Fouling was a lot more common decades ago, when carbureted vehicles would run very rich (too much fuel being burned) or lean (not enough fuel). Today, your fuel burn is tightly controlled by an engine computer and the main cause of spark plug fouling is oil consumption.

Every engine burns oil in tiny, almost undetectable amounts. However, when this oil burning becomes excessive, the oil leaves deposits that build up on the spark plugs. Eventually this causes the spark plug to stop firing. The oil consumption may be due to a crankcase ventilation system issue; worn-out piston rings; or other mechanical issue. Replacing the spark plug will temporarily fix the issue, but a lasting repair will include diagnosing and correcting the oil consumption problem as well. 

Replacing spark plugs in Airdrie: 

Spark plug replacement is a fairly straightforward job for the mechanically inclined. On some engines, the intake manifold or other parts will have to be removed to gain access to the spark plugs. The spark plugs will be hidden underneath either the spark plug wires, or the ignition coils, depending on the engine.

Before removing the old spark plugs, the area must be carefully cleaned to ensure that no dirt or debris falls inside the engine as the spark plug is removed. Once the gap of the new spark plug is checked, it can be installed and torqued. Proper torque is crucial to ensure the cylinder head is not damage; the plug stays tight; and that the spark plug is pointed correctly inside the cylinder. 

Looking for a quality, lasting spark plug replacement? We’d be happy to help! We’ll carefully select the right spark plug for your engine, and give you a good quality install with all the “little things” done right. Our 3 year/100,000 km parts and labour warranty helps guarantee that your new spark plugs will provide trouble-free performance for years to come.