How to Inspect Car Spark Plugs Like a Pro

  • By: Jose Whitmore
  • Date: June 17, 2023
  • Time to read: 9 min.

To check spark plugs in a car, remove the plugs and inspect them for any damage or wear. Maintaining and checking spark plugs is essential for the smooth operation of a car engine.

Spark plugs’ role is to ignite the air-fuel mixture in the engine cylinders and convert them into energy. Over time the spark plugs can accumulate deposits causing a misfire or reduced engine performance. To avoid such problems, timely inspection and replacement of spark plugs are necessary.

To check spark plugs, you will need appropriate tools like spark plug sockets, ratchet wrench, and a gap gauge. In this article, we will explain how to check spark plugs step-by-step, so you can keep your engine running smoothly.

Before You Begin: Gather Necessary Tools

Listing The Tools Required To Inspect Car Spark Plugs:

Before diving into inspecting spark plugs, it is crucial to have the right tools on hand to ensure a smooth and efficient process. By having the following tools readily available, you can save time and reduce frustration:

  • Spark plug socket: This specific type of socket has a rubber lining to grip and safely remove the spark plug.
  • Socket wrench: Used to turn the spark plug socket.
  • Extension bar: This bar is used with the socket wrench to reach spark plugs that are situated in hard-to-reach locations.
  • Spark plug gap gauge: Used to measure the distance between the center electrode and ground electrode of the spark plug.
  • Torque wrench: Used to properly install the spark plug with the recommended amount of torque.
  • Wire feeler gauge: Used to inspect and adjust spark plug gaps.
  • Cloth or rag: Used to clean debris and oil residue from the spark plug and surrounding area.

By having these tools readily available, you can perform a proper and thorough inspection of your car’s spark plugs without any unnecessary hassle or frustration.

Step-By-Step Guide On How To Inspect Car Spark Plugs Like A Pro

Spark plugs play a vital role in the proper functioning of your car engine, as they provide the necessary electrical spark for igniting the fuel mixture. Ignoring faulty spark plugs can lead to a decrease in performance and fuel efficiency, and in some cases, can lead to more serious engine problems.

In this step-by-step guide, we’ll show you how to inspect your car’s spark plugs like a pro.

Preparing The Car For Inspection

Before we begin inspecting the spark plugs, we need to prepare the car. Here’s what to do:

  • Allow the engine to cool down completely
  • Disconnect the negative battery cable to avoid electric shock
  • Gather the necessary tools: Spark plug socket, socket wrench, gap gauge, and a wire brush or cloth for cleaning

Locating The Spark Plugs

Depending on the car model, the spark plugs may be located on the engine’s top or sides, under a plastic cover or individual spark plug wires. Here are the typical locations:

  • In-line engines: Under the hood, follow the spark plug wires to locate each spark plug
  • V-engines: Follow the spark plug wires, or use a service manual to locate each spark plug

Removing The Spark Plugs

Once you’ve located the spark plugs, it’s time to remove them:

  • Use the spark plug socket and socket wrench to carefully loosen each spark plug
  • Unscrew each spark plug by hand
  • Pull the spark plug out gently using pliers or your fingers

Inspecting The Spark Plugs

Now we get to the detailed part of the inspection process. Here are the things you should observe:

  • Check the spark plug’s condition: The electrode and insulator should be clean and without cracks
  • Check the spark plug’s color: Brown or light gray is good; black or oil-soaked indicates that something’s wrong with the engine
  • Check the spark plug’s gap: Use a gap gauge to ensure that the gap is correct
  • Check for deposits: If there are deposits on the spark plug, this may indicate that the fuel mixture is too rich
  • Check the electrode condition: A worn-out electrode may cause engine misfire or low fuel economy

Highlighting Common Issues To Look Out For

In addition to the general inspection, here are some common issues to look out for:

  • Oil-fouled spark plugs: This may be caused by worn-out piston rings, damaged valve seals, or clogged pcv valve
  • Wet-fouled spark plugs: This may be caused by a flooded engine, faulty ignition, or leaking fuel injectors
  • Pre-ignition damage: This may be caused by incorrect spark plug heat range, an overheating engine, or a lean fuel mixture

Cleaning/Replacing The Spark Plugs

If the spark plugs are dirty or damaged beyond repair, you have two options: cleaning or replacement.

  • Cleaning: Use a wire brush or cloth to remove any deposits or buildup on the spark plugs. Do not use abrasive materials or harsh chemicals.
  • Replacement: If the spark plugs are worn out or damaged, it’s time to replace them with new ones. Make sure to use the right type of spark plugs for your car’s engine.

Re-Installing The Spark Plugs

Once the spark plugs are clean or replaced, it’s time to reinstall them:

  • Thread the spark plugs by hand first to avoid cross-threading
  • Tighten the spark plugs with the spark plug socket and socket wrench, following the manufacturer’s torque specifications
  • Reattach the spark plug wires and the negative battery cable

Testing The Car

After you’ve reinstalled the spark plugs, it’s time to test the car:

  • Start the engine and listen for any unusual noises or vibrations
  • Check the engine performance and acceleration
  • Monitor the fuel economy and emissions

Congratulations, you’ve just learned how to inspect your car’s spark plugs like a pro! Remember to perform regular spark plug maintenance to keep your engine running smoothly.

Identifying And Troubleshooting Spark Plug Issues

Spark plugs are a crucial component of your car’s engine and vital for its smooth functioning. Noticing issues with the spark plugs early and taking care of them can help save you from costly repairs in the future. Let’s look at common issues that can occur with spark plugs, symptoms of a spark plug issue, steps to take when troubleshooting spark plugs, and recommendations for cleaning or replacing spark plugs.

Discussing The Common Issues That Can Occur With Spark Plugs

Spark plugs can suffer from various problems, some of which are:

  • Fouling: Fouling occurs when the spark plug gets coated with oil, carbon, or debris, and will result in the engine misfiring, poor acceleration, and reduced fuel mileage.
  • Wear and tear: Spark plugs can wear down over time due to use and will cause problems such as difficulty starting the car, reduced gas mileage, and poor engine performance.
  • Corrosion: Corrosion gathers on the terminals and insulators, leading to poor connection, which will cause the engine to misfire or not start the car at all.

Highlighting Common Symptoms Of A Spark Plug Issue

Here are some common symptoms of a spark plug issue:

  • The car has difficulty starting or fails to start altogether.
  • The engine is misfiring or experiencing a reduction in power.
  • The car has reduced fuel efficiency, and the gasoline emits an unusual smell.
  • The car shows a warning light on the dashboard.

Detailing The Steps To Take When Troubleshooting Spark Plug Issues

If you notice any of the common symptoms mentioned above, try these troubleshooting steps:

  • Disconnect the spark plug wire and remove the spark plug.
  • Inspect the spark plug for visible damage such as carbon buildup, oil residue, or wear.
  • Measure the gap size between the central and the side electrode with a feeler gauge. Make sure it matches the manufacturer’s specifications.
  • Replace the damaged spark plug or clean it using a spark plug cleaner.
  • Reinstall the spark plug and reconnect the wire.

Providing Recommendations On When To Clean Versus Replace Spark Plugs

It’s best to follow the manufacturer’s recommendations for replacing spark plugs. In general, manufacturers suggest a 30,000-mile or 100,000-mile replacement interval, depending on the spark plug type. Cleaning spark plugs is a temporary fix, but it can help extend their life.

Damaged or worn spark plugs will need replacing immediately to avoid engine damage.

It’s essential always to detect and troubleshoot any spark plug issues early on to avoid more significant problems. Make sure to follow the manufacturer’s recommendations for cleaning or replacing spark plugs, and if you notice any unusual symptoms, refer to our steps for troubleshooting spark plug issues.

Frequently Asked Questions About Inspecting Car Spark Plugs

Addressing Common Questions About Inspecting Car Spark Plugs

One of the essential aspects of car maintenance is inspecting your car’s spark plugs. These small plugs help ignite the fuel, ensuring that your car runs smoothly. Here are some of the frequently asked questions when it comes to inspecting spark plugs.

How Often Should Spark Plugs Be Inspected?

Regular spark plug inspection is necessary to keep your car in good working order. The frequency of the inspections, however, depends on the make, model, and age of your vehicle, as well as your driving habits. Here are some guidelines to consider:

  • Check your owner’s manual to establish the recommended inspection interval.
  • For modern cars with electronic ignitions, spark plugs can last up to 100,000 miles, so check your owner’s manual for the recommended period.
  • For older cars with distributor-based ignition systems, spark plugs should be inspected every 30,000 miles or more frequently if you notice any issues.

What Should One Consider When Choosing Spark Plugs?

Choosing the right spark plugs is essential to keep your car running efficiently. There are several factors to keep in mind, including:

  • The make and model of your vehicle. Ensure that you get spark plugs that are compatible with your car’s make and model.
  • Material. Most spark plugs have a copper core, but there are also options with platinum and iridium cores which can last longer.
  • Heat range. Choose a spark plug with a heat range rating that is ideal for your vehicle and engine type.
  • Electrode gap size. This is the distance between the center and ground electrodes. The gap size affects the performance of the plug, so choose one that is suitable for your car’s engine.

Ensuring that you chose the right spark plug will help improve your car’s performance and longevity.

Inspecting your car’s spark plug regularly and choosing the right one is critical to keeping your car running efficiently. Use these tips to ensure that you make the right decisions when it comes to spark plug maintenance.

Frequently Asked Questions Of How To Check Spark Plugs In A Car

How Often Should I Check My Spark Plugs?

It’s recommended to check your spark plugs every 30,000 miles. However, if you experience any engine problems, it’s best to have them checked immediately.

How Can I Tell If My Spark Plugs Need Replacing?

If your engine is misfiring, running poorly, or experiencing a decrease in acceleration, it’s time to check your spark plugs. They may need replacing.

Why Are Spark Plugs Important In Car Maintenance?

Spark plugs are essential as they help ignite the fuel and air mixture in the engine. Without properly functioning spark plugs, your car won’t run efficiently.

Can I Replace The Spark Plugs Myself?

Yes, you can replace the spark plugs yourself with the right tools and knowledge. However, if you’re unsure, it’s best to seek assistance from a professional.

What Happens If I Don’T Check Or Replace My Spark Plugs?

Ignoring your spark plugs can lead to decreased fuel efficiency, performance, and eventually, engine damage. It’s best to keep up with their maintenance.


Now that you’ve learned how to check spark plugs in a car, you can keep your vehicle running smoothly and efficiently. Regular maintenance of your car’s spark plugs can improve acceleration, fuel efficiency, and the overall performance of your engine.

Remember to follow the recommended maintenance schedule outlined in your car’s owner’s manual and replace your spark plugs as needed. The process is relatively simple and can be done with basic tools, but if you are unsure or uncomfortable with the process, it’s always best to seek professional help.

Neglecting your spark plugs can lead to costly repairs and decreased performance, so take the time to perform routine maintenance and keep your car running in top-notch condition. With these tips and guidelines, you can ensure that your engine is firing on all cylinders and operating at its best.

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