How to read spark plugs

Automotive spark plugs create the spark needed in the combustion cycle. Check spark plugs to improve engine efficiency and performance.

Spark plugs can provide valuable information about your vehicle's performance and predict potential problems. Learning how to read spark plugs is quick and easy, and it can equip you with the skills to know when to change spark plugs for optimal performance.

In short, reading a spark plug involves assessing the condition and color of the spark plug tip. Most often, a light brown color around the tip of the spark plug indicates a healthy and well-running engine. If the tip of the spark plug is a different color or condition, this indicates a problem with the engine, fuel system, or ignition. Follow the steps below to learn how to read your car's spark plug.

Part 1 of 1: Checking the condition of the spark plugs

Necessary materials

• Ratchet socket wrench
• Extension

Step 1: Remove spark plugs. Refer to your vehicle's service manual for the location of the spark plugs, their number, and instructions for removing them.

Depending on your vehicle, you may need a ratchet socket wrench and extension to remove the spark plugs. Inspect your spark plugs by comparing them to the diagram above to familiarize yourself with the condition of the spark plugs and engine performance.

• A warning: If you started the car before checking the spark plugs, let the engine cool down completely. Your spark plugs can be very hot, so be sure to leave enough time to cool. Sometimes the plug sticks in the cylinder head if the engine is too hot during removal.

• Functions: Take and check the readings of one spark plug before moving on to the next, as removing too many spark plugs at the same time can lead to confusion later on. If you decide to put the old spark plugs back in, they will need to be put back in place.

Step 2: Check for soot. When you first start inspecting a spark plug, check for black deposits on the insulator or even the center electrode.

Any buildup of soot or carbon indicates that the engine is running on rich fuel. Simply adjust the carburetor to achieve full burn or diagnose the problem. Then soot or soot should no longer fall on the insulator nose of any of the spark plugs.

• Functions: For more help on adjusting a carburetor, you can read our How to Adjust a Carburetor article.

Step 3: Check for White Deposits. Any white deposits (often ash-colored) on the insulator or center electrode often indicate excessive consumption of oil or fuel additives.

If you notice any white deposits on the spark plug insulator, check the valve guide seals, piston oil rings and cylinders for problems, or have a qualified mechanic have the leak diagnosed and repaired.

Step 4: Check for white or brown blisters.. Any white or light brown blisters with a bubbling appearance may indicate a fuel problem or the use of fuel additives.

Try a different gas station and different fuel if you tend to use the same gas station.

If you do this and still notice blisters, check for a vacuum leak or see a qualified mechanic.

Step 5: Check for blackheads. Small black pepper spots on the tip of the spark plug may indicate light detonation.

When this condition is severe, it is also indicated by cracks or chips in the plug insulator. In addition, it is a problem that can damage intake valves, cylinders, rings, and pistons.

Double check that you are using the type of spark plugs with the correct heat range recommended for your vehicle and that your fuel has the correct octane rating recommended for your engine.

If you notice that the spark plugs you are using are out of range for your vehicle's temperature range, you should replace your spark plugs as soon as possible.

Step 6: Change Your Spark Plugs Regularly. To determine if a plug is old or new, inspect their center electrode.

The center electrode will be worn or rounded if the spark plug is too old, which can lead to misfiring and starting problems.

Worn spark plugs also prevent a car from achieving optimal fuel economy.

• Functions: To learn more about when to replace spark plugs, visit our How Often to Replace Spark Plugs article.

If old spark plugs are left unreplaced long enough, damage can be done to the entire ignition system. If you are not comfortable replacing spark plugs yourself or are unsure which spark plugs to use, consult a qualified mechanic to determine the best course of action. If you need a spark plug replacement, an AvtoTachki technician can come to your home or office to perform this service for you.

To learn more about spark plugs, you can also read our articles How to Buy Good Quality Spark Plugs, How Long Do Spark Plugs Last, Are There Different Types of Spark Plugs, and Signs of Bad or Faulty Spark Plugs. ".