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When To Change Spark Plugs (5 Signs + Solutions)

March 18, 2022

A spark plug replacement is an integral fix that you need to perform at some point. It prevents problems with the combustion chamber, ignition system, gas mileage, and other crucial engine parts. 

But when to change spark plugs? 
Are there any signs that signal a bad spark plug? 

In this article, we’ll answer all your spark plug questions, including when to change them, signs to look out for, and what happens if you don’t change your spark plugs. We’ll also check out a convenient spark plug replacement solution.

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Let’s get started! 

When To Change Spark Plugs?

It depends. What’s the make and model of your plugs?

Not all spark plugs can go 100,000 miles without needing a replacement. The typically recommended mileage for changing spark plugs is every 30,000 – 60,000 miles, while extended life spark plugs can go as far as 120,000 miles. 

It’s important to consult your owner’s manual to determine the ideal interval for changing spark plugs. And if that goes missing, you can get your mechanic’s help to figure it out.

Most people keep track of the mileage intervals between each spark plug replacement. You can perform regular spark plug inspections to ensure that they’re not rusted, and that the spark plug gap is appropriately spaced out.

Look out for certain signs that indicate when it’s time for replacing spark plugs. Let’s see what those are.

5 Signs That I Should Change My Spark Plugs

Here are five indicators that your bad spark plug needs changing: 

1. Check Engine Light Is On

Worn, failed, or faulty spark plugs can trigger your check engine light. Depending on what car you drive, you could either see a persistent light showing up, or your check engine light will keep flashing. 

This could indicate misfires that are already happening inside your engine. In this case, it’s best to have your mechanic look at the engine to find the root of your problem.

2. Car Won’t Start

Your spark plugs are responsible for the ignition of an electric spark that gets the vehicle going. So naturally, if you have an old plug or a worn spark plug, your car will have trouble starting

It can also be due to a loose or faulty spark plug wire or worn-out spark plug boot. In this case, you’ll need to perform an inspection to prevent engine and spark plug failure. 

3. Decreased Fuel Economy

Worn-out spark plugs fail to burn the fuel that passes through the engine efficiently. As a result, you need more frequent fuel refills. 

In fact, a faulty or fouled spark plug can reduce your car’s fuel economy by almost 30 percent! 

4. Rough Idling And Excessive Noise

A fouled spark plug that fails to create a spark will cause a lot of engine noise and rough idling. In the best-case scenario, your vehicle will make some soft sounds. You should be able to hear these while turning on your engine. 

In the worst case, you may hear excessive rattling, pinging, knocking, or clicking sounds from your engine. 

5. Poor Acceleration 

Any unusual behavior in terms of handling or poor acceleration can be an indicator of a failing spark plug or a bad spark plug that needs changing. Your vehicle usually becomes unresponsive as a result of inconsistent electric sparks from the spark plugs. 

Now that you know when changing spark plugs might be needed, how do you go about inspecting them?

How To Inspect Your Car’s Spark Plugs (Step-by-Step)

To inspect a potentially failing spark plug, you’ll first need to remove the old plug. 

Here’s how: 

  1. Start by locating the old plug near the ignition coil or ignition coil cover. Locate the spark plug wire connected to the ignition coil. Gently pull on the spark plug boot. (Be careful not to pull on the wire) 

    Note: Make sure to clean the cylinder head area around the old plug of debris (to prevent dirt from falling into the engine) before taking it out.
  1. Once the wire or coil is removed, use a socket wrench with a spark plug socket to remove the old spark plug. Place the spark plug socket around the spark plug and turn the socket wrench clockwise. (You can also use a torque wrench) 
  1. Take out the old plug and blow some compressed air over it to clean the dirt. Observe for any signs of wear. 

A worn spark plug will feature a dirty spark plug boot, carbon-fouled plugs, or a damaged spark plug wire. A failing spark plug will have visible signs of wear and tear (including broken electrodes and an uneven spark plug gap). 

If you spot any of these, it’s best to replace your faulty spark plugs with a new plug. Both old and new vehicles require regular maintenance for efficient functioning. Getting a new spark plug ensures that your ignition system remains healthy.

That said, what happens if you don’t replace your faulty spark plugs? 
Let’s find out.

Why Do I Need To Change Old Spark Plugs?

Routine spark plug replacement and regular maintenance are crucial to maintaining the functioning of your internal combustion engine and keeping your car running smoothly. 

For one thing, when a worn spark plug fails to generate an adequate electric spark, the combustion of the air fuel mixture becomes incomplete. 

Consequently, an old spark plug will lead to engine misfires, rough idling, and problems with gas mileage that result in a loss of engine power and occasionally engine failure. 

Eventually, an old spark plug will also affect the other engine parts. This may lead to costly repairs, and you may even need to get some parts replaced. 

So is there a way to fix bad spark plugs? 

What Is The Best Spark Plug Replacement Solution? 

A spark plug replacement can be pretty straightforward and easy to perform. But if you’re not confident about it, a reliable mechanic is your best option.

Why not give RepairSmith a try? 
RepairSmith is a mobile auto repair and maintenance solution with a range of services for your car. We offer competitive and upfront prices and a 12-Month | 12,000 Miles warranty on all our repairs. And your car will be serviced by top ASE-certified mechanics. 

Fill up this form to get a cost estimate for new spark plug replacement! 

Closing Thoughts

A bad spark plug can cause a lot of problems, including reduced gas mileage (which affects fuel economy), poor acceleration, engine wear, and difficulty starting the car. 

Luckily, all you need to do is get a replacement within your recommended mileage intervals, or when faulty spark plugs start making an appearance. 

Routine spark plug inspections are a great preventive measure. 
So, if you need any help with that or any other car maintenance, contact RepairSmith

Simply fill out this form to book an appointment for our mechanics to drop by your driveway.