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How To Read Spark Plugs? [WHEN AND WHY YOU NEED TO?]

How To Read Spark Plugs? [WHEN AND WHY YOU NEED TO?]

Reading spark plugs is a process comprising several steps, including evaluating the spark plug's color and condition. It is one of the best ways that you can use to learn about the performance of your vehicle and identify potential problems before they occur.

You must pay close attention to several signs when reading the spark plugs. Signs such as eroded electrodes, burnt electrodes, flattened or broken electrodes, Grayish-tan deposits, and dry and black soot all point toward the possibility of a problem with your spark plug.

Since the information you get from reading the spark plugs tells you more about your vehicle's condition, you should ensure that you get the reading right. Read on to learn more about how and when to read spark plugs.

spark plugs

How To Read Spark Plugs

If your spark plugs are damaged, they can result in more complex problems, including slow acceleration, reduced gas mileage, trouble starting the engine, and engine misfires. You do not have to wait until you experience engine problems before you can think of examining the condition of your spark plugs.

To read the spark plugs, you only need to remove the spark plug you want to look at from the engine. Take the Plug in your hand and start examining for signs that may provide you with more information about the condition of your engine. When examining the spark plugs, you are likely to take note of the following conditions.

Normal Spark Plug

A normal spark will have an ordinary look with everything intact. The color is either brown or grayish-tan deposits on the electrode. Since the Plug is in perfect condition, you can reinstall it.

Oil Deposits

One of the signs you are likely to notice on damaged spark plugs is black oily deposits on the insulator tip points and in the electrodes. The sign indicates that there could be an oil leak into the cylinders and get past the worn-out pistons or valve guide. You will need to find the source of the leak as soon as possible.

Carbon Fouled

If you spot black, dry soot on the insulator tip and electrodes, that indicates a carbon-fouled plug. In most cases, such a problem can result from excessive driving at low speeds, a dirty air filter, or your vehicle idling for too long. You will need to replace the spark plugs with the right ones.

Burned Electrodes

If you see blisters on melted electrodes, insulator tips, or white deposits, those are signs of a burnt spark plug. The causes for this problem may include a loose spark plug, incorrect spark plug heat range, too lean of air/fuel mixture, or incorrect ignition timing. The proper action is to replace the spark plugs as soon as possible.

Broken Electrodes

Installation of wrong spark plugs may lead to flattened or broken electrodes. A short spark plug can cause poor gas mileage, while too long can result in catastrophic damage to your engine. It is essential to check the owner's manual to be sure that you have the correct spark plugs on your vehicle.

Worn Electrodes

If you notice worn electrodes when doing your spark plug examination, that should tell you that the spark plugs have passed their prime time and, therefore, need to be replaced.

Spark Plug Cross Reference

While spark plugs do not require regular replacement, there are some instances where you will need to replace them. After examining the spark plugs for your vehicle and concluding that they are not in perfect condition, it is vital to contact a professional for spark plug cross reference to avoid unnecessary inconveniences.

Changing the spark plugs on your vehicle can have numerous benefits, including;

  • Enhancing the optimum performance of the combustion engine
  • Increasing the fuel efficiency of the vehicle
  • Guaranteeing excellent start-up performance
  • Improved horsepower
  • Reduced carbon emissions

How to Clean Spark Plugs

Spark plugs are essential components of a vehicle as they play a significant role in ensuring that the vehicle runs smoothly. Cleaning the spark plugs can help reduce the need to carry replacement now and then, as that can prove quite expensive.

Fortunately, cleaning the spark plugs is a simple task that does not necessarily require the input of a mechanic to execute it successfully on your own.

The cleaning process starts by locating the spark plugs and then removing them for cleaning. Do not attempt to clean the spark plugs without removing them from the engine. The right approach is to remove the spark plugs from the engine and then decide on the proper cleaning method.

There are several cleaning methods that you can use to clean your spark plugs, including the following;

Cleaning with Abrasive

If you notice that the electrode of your spark plugs is discolored, you can use a piece of sandpaper to gently clean the electrode until there is no piece of carbon left. Besides a piece of sandpaper, other abrasives that you can employ include a file, wire brush, and carb cleaner.

The Use of a Blow Torch

Another method to embrace is the use of a blow torch. Since the blow torch will make the spark plugs extremely hot, you will need a pair of pliers to make your work easier. The blow torch works by burning off all the debris, oil, and junk on the plugs.

The Use of a Spark Plug Cleaner Tool

The use of a spark plug cleaner tool is another effective method that you can use to clean the spark plugs of your vehicle. The spark plug tool is designed for sandblasting the spark plugs to remove any dirt and render the spark plugs clean.

How to Read Spark Plugs for Tuning

The spark plug color mirrors the condition of the engine. Hence you can use it for tuning. However, tuning with a spark plug alone can be misleading in some situations.

After removing the spark plug from the engine, you need to examine it before you can draw any meaningful conclusions. If the spark plugs are black or sooty, that indicates too rich fuel/mixture hence the need to adjust it.

If it is yellow or white, this indicates a too-lean air/fuel mixture. Further, if the electrodes are worn out, then it means that you need to replace the plugs as soon as possible.

car spark plugs

How to Read 2 Stroke Spark Plugs

If you are tuning your engine, you must ensure that you do it correctly to gather as much information about it as possible. That way, you will be able to prevent mechanical problems in your vehicle before the situation gets out of hand. To read 2-stroke spark plugs, you need to follow these steps.

  1. Remove the Plug from the engine – you need to be careful not to touch the electrode with your fingers when removing the spark plug from the engine. Touching the electrode with your finger can damage it.
  2. Examine the Spark Plug

After removing the spark plug from the engine, the next essential step is to examine it for any signs of wear or damage closely. If everything looks great, then you should move to the second step, which may entail using the multimeter or ohmmeter to gauge the resistance of the spark plug. Ensure that the reading is within the specifications of the manufacturer.

If you do not have a multimeter or ohmmeter, you use visual inspection to learn more about the condition of the spark plugs. However, if you decide to use visual inspection, you will need to clean the debris or any deposits from the electrode first. Once it is clean, hold it through a light source and closely examine it.


Reading the spark plugs is a straightforward process that should never give you an arduous task. Considering that the spark plugs provide more information about the performance condition of the engine, you should ensure that you get it right. Moreover, reading the spark plugs can help prevent further damage to your vehicle's performance.