When a spark plug fails, it can cause various problems with your car.

Bad spark plug symptoms

1. Poor fuel economy

If your car isn’t getting as good of gas mileage as it used to, it may be because of bad spark plugs. A misfiring plug can cause your engine to run rich, which means it will use more fuel than necessary.

2. Hard starting

If your car has trouble starting, it may be due to a bad spark plug. When a plug is worn out or fouled, it can be difficult for the engine to create the spark needed to start.

3. Rough running

 A misfiring plug can cause the engine to run on only two or three of its cylinders, which will make it run very unevenly.

4. Check engine light

If your check engine light comes on, it may be because of a bad spark plug. A misfiring plug can cause all sorts of problems with the car’s emissions system, which will trigger the check engine light.

5. Smoking

If your car is smoking, especially from the exhaust pipe, it may be because of a bad spark plug. A fouled or worn-out plug can cause the engine to run too rich, which will result in black smoke coming out of the exhaust.

6. Decreased performance

If your car is performing worse than usual, it may be because of bad spark plugs. A misfiring plug can rob your engine of power and torque, making it hard to get up to speed.

7. Engine knocking

If you hear a knocking noise when your engine is running, it may be because of bad spark plugs. A worn-out or improperly gapped plug can cause the engine to knock or ping when you accelerate.

What are the expenses of replacing your spark plugs?

The cost of a new set of spark plugs generally ranges from $3 to $15, depending on the make and model of your vehicle. If you have a plug that needs to be replaced, the labor cost typically falls between $50 and $100. In general, it’s a good idea to replace your spark plugs every 30,000 miles or every two years, whichever comes first.

If you’re not sure whether it’s time for a new set of spark plugs, take your car in for a tune-up and let your technician make the judgment.

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When should you change the spark plugs on your car?

The spark plugs should be replaced every 50,000 miles, according to Kia. If you are experiencing poor gas mileage or other performance-related problems, you could have a clogged or faulty spark plug that needs immediate replacement.

How can you change the spark plug on your car?

Use a spark plug socket (or suitable deep socket) and attach it to your ratchet. Place the socket over the top of the plug and give it a good tug, turning it counter-clockwise as you do so. If the plug is stubborn and doesn’t want to come loose, spray a little penetrating oil on the threads and try again. Once the plug is loose, slowly unscrew it by hand until it’s completely removed from the engine.

Be sure to dispose of your old spark plugs properly by recycling them or taking them to a hazardous waste center. You have to reattach the new plugs and tighten them with the socket and ratchet. Reattach all of your wires and replace any removed parts such as the filler cap, negative battery cable, etc. Once everything is put back together, turn your ignition on and start up your engine. Check for any leaks around each plug to ensure it’s tight enough. While running, turn off your engine once more to see if there’s an increase in acceleration or performance. If so, job well done!

Tips for keeping your spark plugs in good working order

With proper care, your spark plugs can last for many years. By following these simple tips, you can ensure that they remain in good working order and help your engine run smoothly.

Here are a few tips for maintaining your spark plugs:

  • A buildup of dirt and gunk can affect the plugs’ performance. Neat your spark plugs.
  • Check the plugs for damage or wear. If they’re worn down, it’s time for a new set.
  • Avoid over-tightening the spark plugs when you install them.
  • Ensure the plug wires are in good condition and properly connected to the plugs. Wires that are cracked or loose can cause poor performance.


Bad spark plugs can cause a variety of problems with your car. You can buy replacement plugs at most auto parts stores.


  • How do I know when to replace my spark plugs?

The best way to determine when your spark plugs need to be replaced is to check your vehicle’s owner’s manual. The manufacturer will typically list a suggested replacement schedule based on your vehicle’s make, model, and year. You can also consult a trusted mechanic to get an expert opinion.

  • What are the signs that my spark plugs need to be replaced?

If your engine is misfiring, has decreased performance, or consumes more fuel than usual, it may be time for new spark plugs. Additionally, if your spark plugs are corrupted or damaged, it’s best to replace them as soon as possible.

  • How much do spark plugs cost?

The cost of replacing your spark plugs will vary depending on the make and model of your vehicle. You can expect to pay anywhere from $50 to $200 for a new set of spark plugs.

  • Are there any steps I can take to prolong the life of my spark plugs?

There are a few things you can do to help prolong the life of your spark plugs. If you’re not using your vehicle regularly, consider removing the spark plugs and storing them in a safe place. It would help if you also avoided over-tightening

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