What Causes Black Carbon On Spark Plugs?

One of the indicators that your spark plugs have been harmed is when their tip starts to change color. Usually, a spark plug’s insulator tip and electrodes turn black and dry due to a carbon-fouled plug. 

But what causes carbon fouling? 

This sign of harm indicates a possible rich air-fuel mixture, too low engine temperature, or long vehicle idling. An imprudent driving at a low speed can also cause carbon fouling to your spark plugs. 

Meanwhile, a spark plug misfire is its possible effect since carbon deposits are conductive, which creates a path for it. However, you can treat this harm immediately by replacing the damaged plug. 

Please keep reading to know more about reading spark plugs and other ways to prevent and fix them. 

Things You Should Know In “Reading” Your Spark Plugs

YouTube video

In the past, cars had many ignition parts like spark plug wires, which are nonexistent. However, up to this date, whether vintage or modern, one part that has remained is spark plugs.

It provides ignition and heat while your engine is in use. 

Moreover, spark plugs are also a great identifier of your engine’s overall health. The video from MotorWeek showcased six different looks of spark plugs and the reasons for such looks. 

The first spark plug sample is seen to have a noticeably worn material at the center of the electrode.

The usual dirty white tip has slightly turned bronze while some parts of the thread gradually transform into black.

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It’s normal, though. This spark plug looks like a normal worn-out plug that has traversed many miles already.   

The next one is the black, dry, and sooty-looking spark plug. This plug is an example of black carbon caused by a rich mixture of fuel and air. 

A carbon fouling might also indicate that your engine has a leaky fuel injector or a general fuel control problem.

On the other hand, spotlessly clean plugs usually mean that your engine’s coolant goes through the cylinder. Its stem cleans other spark plugs.

If your plugs have a bit of discoloration, that is what you wanted to see. It signifies that your electrodes are equal and your engine is perfectly working. 

Since there is something you want to see, what you don’t want are dry and sandy texture spark plugs.

This spark plug look indicates that your engine is sucking the oil in very fine pieces around the valve seals or guides.

Lastly, when the tip of your plug is wet and greasy, it might be a liquid coming from the engine’s bottom. In this case, you might need a major engine internal repair. 

Frequently Asked Questions

Why do the spark plugs turn black? 

There are three main reasons why spark plugs turn black: carbon fouling, oil deposits, or simply worn-out.

When you see your spark plugs changing color, have it examined as it might trouble your oiler and engine starting. 

In assessing the plug, the first thing you must do is read the spark plug to check what happened. From there, identify the probable cause. If you need help from an expert, don’t hesitate to do so. 

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How can I prevent carbon fouling?

Most carbon fouling is caused by excessive driving, even if the engine is not heated enough to run. So, one thing that you can do is to let your engine warm-up before running it, even for a short distance. 

Sometimes, carbon fouling is also about the fuel you use. That’s why it’s best to use a fuel that matches your engine well. Keeping the fuel injectors in excellent condition and having spark plugs with perfect heat range also help. 

What can I do to fix my broken spark plugs?

Aside from changing your spark plugs, you can also clean them in different ways. You can easily use a machine that spews sands to remove the carbon from your plugs. This method is called sandblasting. 

You can also remove the carbon in your plugs using a butane torch, wire brush, or sandpaper. Last is the most basic, which is the application of a spark plug cleaner.

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