Your spark plug’s electrode or porcelain tip has a shiny black appearance and just isn’t working like it should. This is what happens when oil finds its way into the combustion chamber.
Plugs should make it to the recommended service interval without issue, as long as you pick the right metallurgy for your needs and make sure to install them correctly. If fouling is causing misfires long before the plugs are supposed to be changed, you’ve got a bigger problem on your hands.
Oil fouling is one of the most common types, but it could be a sign of something more serious – advanced engine wear. If you start to see oil deposits on your spark plugs, you need to diagnose the cause before you get right into plug replacement.
Oil doesn’t belong in the combustion chamber, but piston rings, valve stem seals or the PCV system can have other ideas. Here are a few things you can try to get to the bottom of it:
Not only can these tests save you from ruining even more plugs, they can save your engine from continued damage. Last time I checked, those cost a pretty penny too.
Give those spark plugs the right twist or your engine could end up paying the price. These are the steps the pros follow:
Grab a thread chaser and a torque wrench.
Screw new plugs in by hand until tight. If a plug tightens up too soon while turning them in by hand, use your thread chaser to clean the threads.
Use your torque wrench to tighten the spark plugs according to manufacturer’s recommendations OR refer to the torque chart in the Autolite Spark Plug Catalog.
Verify that you’ve installed your plugs correctly by starting the engine. No misfires or a rough idle? Congrats kid, you’ve got your torque down.
To all my people who loved the garage more than school growing up, I’m sure you’ve heard about the way engines are trending. Gasoline Direct Injection (GDI) engines continue to grow in popularity, and if you have one (or are working on one for your ungrateful relatives, friends, kids, etc.), you’ll need to understand its particular ignition needs.
Auto manufacturers have leaned into GDI technology for a reason. This type of engine delivers better performance and fuel economy over conventional fuel injection systems, but it also comes with unique service requirements and challenges. Yes, these requirements include specific spark plug needs.
The key difference in these engines is that they directly inject fuel at high pressure into the combustion chamber. Because this process is more likely to fuel wash spark plugs than indirect fuel-injection systems or conventional carburetors, a GDI engine calls for spark plugs with more focused ignition.
Here’s another factor you should consider when it comes to GDI. More complete combustion and cooler temperatures inside the cylinder lead to an enhanced compression ratio that delivers better efficiency and power with the same amount of fuel. BUT these cool temperatures can also be more likely to create carbon fouling.
Direct injection also brings the risk of introducing small amounts of dirt in the air and blowback carbon build up on intake walls. This carbon buildup could restrict air flow to the cylinders, causing the loss of torque and fuel economy.
So, the main advantage of GDI technology – its precision – makes finding the right plug just a little more difficult. To keep these engines running cleanly and efficiently, you need to know your metallurgy.
Focused ignition, an optimal heat range and superior fouling resistance are a winning combo for any engine, but they are non-negotiable for direct injection. That’s why you’ve gotta get iridium.
Autolite® offers two options in this category, Iridium Ultra® and Iridium XP, both are proven to deliver high power, long life and exceptional value. Iridium XP offers an ignition upgrade for older vehicles, while Iridium Ultra® is an ideal OE replacement, especially in late models.
Look at you, you’re a GDI expert now!
I’m not British, but I still think mind the gap is some of the most useful advice I can give. Successful ignition and kick-ass performance are only possible with the right spark plug gap.
This gap, or the proper distance between the center and ground electrodes, is a delicate balance. Proper distances come down to a tenth of a millimeter or four thousandths of an inch. Without the right distance, the plug may not be able to ignite the air-fuel mixture or create the necessary combustion to start an engine.
Too small of a gap and the flame kernel may not have enough room to expand. Too large and the voltage required from the coil may be too great. Because spark plugs are precision-made, any adjustment has the potential to greatly affect that performance we crave. This is especially true of new iridium plugs.
Even though iridium spark plugs can potentially deliver more than 100,000 miles of ignition, 0.6mm or 0.5mm iridium finewire can be destroyed during gapping. A combination of a steady hand and a trusty gapping tool is needed to take on this task.
A wire loop gauge is the ONLY gapping tool that is Annie-approved. It’s accurate and offers damage-free operation when used properly. With a selection of wire loops and a hook, this gauge helps in measuring the gap, gently bending the electrode and then re-measuring until correct. Let me say this again. This should be the only gapping tool used in your shop, especially when it comes to iridium finewire.
Before you get to work, look up the right gap as recommended in your owner’s manual or Autolite Spark Plug Catalog.
The makeup, or metallurgy, of the plug’s conductive material can be the difference maker for mileage, service life, fuel efficiency and fouling resistance. Some metals are more resistant to corrosion, are better at resisting fouling and can be machined into a fine wire to produce more focused ignition.
As much as I love fancy words, let’s break down what this means when you’re shopping for new plugs. Here are your electrode options and what they have to offer:
Just like me, iridium is the best and brightest in its family. Iridium is considered part of the platinum family, but it has a much higher melting point. This very durable metal lasts longer against the demanding conditions in the combustion chamber. Normally machined into a fine wire (under 1 mm) application, iridium ignition is more focused. Unlike me, iridium can fracture if you’re not gentle. So be careful when you gap it!
Double platinum ISN’T exactly what it sounds like. It’s not double the efficiency of regular platinum plugs, but it is the ideal metallurgy for very specific applications. An OE-style replacement for distributorless ignition system (DIS) applications, these plugs have two platinum-protected surfaces to guard against wear sparks initiating from the ground electrode, something that is pretty common in a DIS.
This is what we call a noble metal. Platinum is used in higher voltage applications because of its high level of durability. With strong heat resistance, this metal has a high melting point, and it generally features a smaller electrode than its copper counterparts. In addition, platinum plugs can give your baby more complete combustion and improved fuel efficiency over copper.
This metal features extremely high thermal conductivity, important when trying to dissipate heat, a constant threat under the hood. Copper plugs are usually a good fit for older vehicles with conventional ignition systems. Since the start of the new millennium, OE plugs shifted toward platinum and then iridium.
Copper has long been the standard, but newer model vehicles may require a minimum metallurgy of iridium. I can’t stress this enough - check OE specifications when selecting the most applicable aftermarket spark plugs.
If performance is your priority, consistent ignition and quicker acceleration makes iridium the way to go. These plugs can handle a greater mileage load than copper or platinum.
When it comes to installing or removing spark plugs, an eye for detail and a little bit of elbow grease are every bit as necessary as the stuff you keep in your toolchest.
As for the actual tools, I’ve got recommendations there too. Installing and removing spark plugs on your own isn’t tricky, but the right tools go a long way in making it a smooth process.
Here’s what you’ll need:
And that’s it! Now you know the Annie-approved list of tools you’ll need to successfully remove and install spark plugs on your own.
When installing or removing spark plugs, make sure not to stress the ceramic insulator. An uneven socket could cause cracks, and eventually misfires. The easiest way to avoid this issue is to pick a socket recommended for use with spark plugs. Usually, this type of socket will come with a rubber insert to surround and hold the insulator during installation. An even more helpful socket feature is a magnet that can hold the plug terminal in place to make removal from the engine easier.
Spark-plug-specific sockets will often have a hex bolster on the drive end, allowing the use of a wrench to increase usability in hard-to-reach locations. Most engines use either 5/8” or 13/16” hex spark plugs, but if you’re unsure what size socket you’ll need, you can use newly purchased spark plugs to locate a correctly sized socket while at the store.
Pre-ignition can cause severe spark plug damage. This condition occurs when the ignition of the fuel-air mixture happens before the spark plug is ignited, and it’s more likely when you pick a plug with too hot of a heat range for the application.
Hot spots, carbon build-ups in the combustion chamber, lean fuel conditions caused by PCV contamination and low octane fuel are a few other potential causes. No matter the cause, there is a good way to tell if this is happening under your hood. If the ground electrode and insulator are damaged, you could be dealing with pre-ignition.
Prevent pre-ignition and the damage it can cause by using a plug in the recommended heat range for your application, and of course, maintain your engine with regular maintenance.
You could call me the girl next door, that is, if the girl next door knew how to rebuild engines. Growing up with two knucklehead brothers and the best dad I could ask for, we used our weekends to max out muscle cars and give neighbors and family friends a hand with auto maintenance. Spend some time in my garage. You might learn a thing or two.
Ask a Question
What would you like to ask?
What’s your best piece of ignition advice?What’s your best piece of ignition advice?It’s all about the tip! Paying attention to electrode metallurgy keeps your engine in the right performance range.
What kind of cars are you into?What kind of cars are you into?I moonlight as a hot rod builder. Please keep your granola-powered station wagons away from me.
If you were a spark plug, which one would you be?If you were a spark plug, which one would you be?Oh, I’m definitely an iridium plug – dependable, focused and packing a lot of power!
What are you up to when you’re not in the garage?What are you up to when you’re not in the garage?I’m busy being the best dog mom to my boxer Sparky. I also love home improvement shows and belting out country songs.