How To Check If a Spark Plug is Bad – 4 Steps

Knowing how to check if a spark plug is terrible can save you time and money by way of diagnosing the difficulty early and stopping in addition to damage to your engine. We will walk you through an easy four-step procedure of how to check if a spark plug is bad to be able to empower you to with a bit of luck verify the situation of your spark plugs, making sure the greatest performance and efficiency for your car.

What Are the Consequences of a Bad Spark Plug

How To Check If a Spark Plug is Bad

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1. Decreased Fuel Efficiency: A bad spark plug can cause incomplete combustion, causing your engine to burn more fuel than critical and decreasing common fuel performance.

2. Engine Misfires: A defective or old spark plug can cause engine misfires, which result in tough idling and usually reduced performance.

3. Poor Acceleration: With a bad spark plug, your car may additionally warfare to accelerate without difficulty and short, making driving much less thrilling and doubtlessly risky in fantastic conditions.

4. Increased Emissions: When a spark plug is not firing nicely, it can result in higher ranges of dangerous emissions being launched into the surroundings, contributing to air pollutants.

5. Reduced Power: Your automobile can also revel in sluggishness and shortage of the energy it once had whilst running with bad spark plugs, affecting its average normal performance on the road.

6. Risk of Damage to Catalytic Converter: Continuous use of an automobile with bad spark plugs can cause damage to the catalytic converter as unburned gasoline accumulates and gets burned internally.

7. Potential Engine Damage: In intense times, a bad spark plug can motive harm to one-of-a-kind engine components due to strange combustion events and immoderate strain on internal parts.

8. Difficulty Starting the Engine: Faulty spark plugs ought to make starting your vehicle greater hard or unpredictable, leading to frustration and capability transportation troubles.

How To Check If a Spark Plug is Bad – 4 Steps 

How To Check If a Spark Plug is Bad

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Step 1: Removing the Spark Plug

Start by finding the spark plugs – they’ll usually be discovered under a rubber boot on the pinnacle of the engine. Gently twist and pull the boot to reveal the spark plug beneath. As you remove each spark plug from its socket, take care now not to damage the spark plug threads or electrode – those are easy to compromise if not handled with precision. Ensure your automobile’s engine is cool in advance before trying this machine; otherwise, you hazard burning yourself on heat engine components or destructive components because of the thermal boom.

Step 2: Cleaning Spark Plug

Use a cord brush or a specially designed spark plug cleaner tool to eliminate any carbon deposits or corrosion from the spark plug electrode and insulator. Once the seen debris has been removed, use a specialized spark plug purifier solution or a small quantity of fuel to further ease the spark plug. Gently scrub with an antique toothbrush or tender-bristled brush before rinsing with water and allowing it to dry earlier than reinstalling. By well-cleaning your spark plugs, you could ensure higher gasoline efficiency, smoother idling, and improved overall engine performance. 

Step 3: Initial Test

To test the spark plug requires casting off the spark plug from the engine and visually analyzing it for signs of wear, harm, or fouling. Look for a construct-up of carbon deposits or oil on the electrode, which can imply capacity troubles. Ensure that the spark plug gap is inside the manufacturer’s endorsed specs. This critical preliminary takes a look at units at the level for further exam and helps to pick out any obvious issues with the spark plug that may be inflicting troubles together with your engine’s performance.

Step 4: Resistance Check

Resistance check includes the use of a digital multimeter to measure the resistance throughout the terminals of the spark plug. This test permits you to evaluate if any internal faults inside the spark plug can compromise its functionality. By comparing those resistance measurements against the producer’s specifications, you may determine if your spark plugs are in desirable running condition or if they want to be replaced. It’s a fundamental step in diagnosing capability problems together with your spark plugs and making sure ultimate engine overall performance.

The Benefits of Checking Spark Plug

  • Checking spark plugs regularly can help keep an efficient engine’s typical overall performance. A smooth, nicely gapped spark plug promotes easy combustion, which contributes to advanced gasoline performance and top-notch strength delivery.
  • Regular inspection of spark plugs can reveal early signs and signs of ability problems together with carbon buildup, an electrode placed on, or spark plug fouling. Addressing these troubles properly away can prevent top-notch engine harm and highly-priced upkeep down the street.
  • By staying on the pinnacle of spark plug renovation, you can enlarge the lifespan of your engine additives. Well-maintained spark plugs contribute to a cleanser inner combustion procedure, reducing ordinary put on and tear at the engine’s critical elements.
  • Regularly checking and servicing your vehicle’s spark plugs is a clean but crucial workout that could yield numerous blessings to your automobile’s overall performance and sturdiness. 


Checking the circumstances of your spark plugs is a critical aspect of maintaining your vehicle’s performance and gas performance. By keeping an eye out for signs of wear and tear, along with misfiring, rough idling, or terrible acceleration, you can save your capability harm to your engine and save on expensive repairs.

Regularly examining and replacing vintage or faulty spark plugs can substantially improve the overall health and longevity of your car. Remember to consult your proprietor’s manual or an expert mechanic for precise recommendations on when to alternate your spark plugs. Take the time to check your spark plugs frequently and make certain that your car continues to run easily for future years.


1. How to tell if a spark plug is terrible by way of looking at it?

If you observe your spark plug and notice that it’s black, sooty, or oily, then you could know that your spark plug is terrible.

2. How long do spark plugs last?

Spark plugs finally between 80000 to one hundred thousand miles; after that, you want to replace your spark plug.

3. Are spark plugs expensive?

The solution can also rely upon who you ask, however usually, they may be now not too steeply-priced. A spark plug can vary in rate from some greenbacks to upwards of $10. However, bear in mind that most vehicles require four spark plugs so the overall cost can be better. A few luxury vehicles might also require unique or top-rate spark plugs which can price even more. 

4. What is a spark plug resistance chart?

A spark plug resistance chart is a desk that shows the appropriate resistance fee for each kind of spark plug. This statistic ensures that the right spark plug is installed within the engine. Incorrectly set up spark plugs can cause engine harm or negative engine performance.

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