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How Can You Tell When a Spark Plug is Bad (Needs Replacing)?

Close-up of a brand-new car spark plug in the engine bay.

Sparkplugs can last a while before they need to be replaced. However, a few symptoms can help you know it’s time for a replacement sooner. Pay attention to your car’s performance and check your spark plugs if you notice any of the following:

– Decreased fuel efficiency

– Reduced power or acceleration

– Rough idling or engine misfires

– Increased emissions

If you’re unsure whether or not your spark plugs need to be replaced, consult a professional mechanic. They will be able to perform a diagnostic test to check the health of your spark plugs and recommend replacement if necessary.

It’s hard to start the car.

If a sparkplug is terrible, it will be hard to start the car. This is because the sparkplug ignites the air/fuel mixture in the engine’s cylinders. If it is not working correctly, the machine will not start. When the spark plugs are going bad, you may notice that the car takes longer to start than usual.

The engine is misfiring.

Vehicle repair and replacement of spark plugs.

A misfire occurs when the air/fuel mixture in the cylinder doesn’t ignite properly. This can happen for several reasons, but one is a bad spark plug. If you notice that your engine is misfiring, it’s a good idea to check the spark plugs and see if they need to be replaced.

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The engine is idling rough.

If the engine is idling rough, it’s not running smoothly. Various factors can cause this, but one possibility is a bad spark plug. This is because the spark plug is responsible for igniting the air/fuel mixture in the cylinders. If it’s not working correctly, the engine will run rough.

There is decreased fuel efficiency.

One of the symptoms of a bad spark plug is decreased fuel efficiency. This is because the spark plug is responsible for igniting the air/fuel mixture in the cylinders. If it’s not working correctly, the engine will not be able to run as efficiently.

The engine is emitting black smoke.

Black smoke and exhaust are coming from the engine.

If you notice the engine emitting black smoke, it could be due to a bad spark plug. When the spark plug ignites the air/fuel mixture, it can cause incomplete combustion. This can lead to black smoke coming from the exhaust pipe.

The car is running rough.

If the car runs rough, it could be because of a bad sparkplug.

There is decreased power or acceleration.

An up-close view of an ancient vehicle spark plug.

If you notice that your car has decreased power or acceleration, it could be because of a bad spark plug. The acceleration could be affected because the spark plugs are not helping the car have the power it needs.

The engine is making strange noises.

If the engine makes strange noises, it could be because of a bad sparkplug. The noises can be caused by the sparkplug not working correctly. If you notice strange noises from the engine, it’s a good idea to check the spark plugs and see if they need to be replaced.

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The check engine light is on.

Detail shot shows the engine warning light on the dashboard of a car.

The check engine light can come on for many reasons, one of which could be a bad sparkplug. When a sparkplug is terrible, the check engine light will tell you there is a problem. Check the sparkplugs if the check engine light is on.

The car is losing power.

If the car loses power, it could be because of a bad spark plug. This is because the sparkplug is responsible for igniting the air/fuel mixture in the cylinders. If it’s not working correctly, the engine will not be able to run as efficiently and will lose power. Check the sparkplugs if the car is losing control.

How often do sparkplugs need to be replaced?

Close-up image of the replacement of a spark plug.

Sparkplugs typically need to be replaced every 30,000 miles. However, this can vary depending on the make and model of the vehicle. Consult your owner’s manual for specific recommendations.

If you’re unsure whether or not your spark plugs need to be replaced, consult a professional mechanic. They will be able to perform a diagnostic test to check the health of your spark plugs and recommend replacement if necessary.

What does a bad spark plug look like?

A bad spark plug will typically be covered in soot and carbon deposits. In addition, the electrode (the part that emits the spark) may also be damaged or worn down.

How much does it cost to replace a spark plug?

A picture shows someone changing the car's spark plugs while having spark plugs on hand.

Spark plugs typically range in price from $2-$4 each. However, this can vary depending on the make and model of your vehicle. It’s best to consult your owner’s manual or a professional mechanic for specific pricing information.

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Replacing spark plugs is typically a simple and inexpensive repair. However, it’s always best to consult a professional if you’re unsure about how to do it. They can properly diagnose the problem and recommend the best course of action.

How long can you drive with lousy spark plugs?

It would help if you did not drive with lousy spark plugs for too long. This is because they can cause damage to the engine.