Driving With Bad Spark Plugs: The Long-term Effects

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Written By Gabriela
Gabriela is a science journalist and writer. She has a PhD in biochemistry and a master's degree in science communication. Gabriela has published articles in magazines and newspapers in Mexico and USA, and has also given talks on science subjects.






Your spark plugs are one of the most important components of your engine. They are responsible for sparking the fuel to life and propelling your car forward. But what happens if your spark plugs go bad? What are the symptoms of bad spark plugs and what long-term damage can they cause if they’re not replaced? In this article, we’ll answer all your questions about bad spark plugs and what they can do to your engine.

What happens when spark plugs go bad

Faulty spark plugs can lead to an engine misfire, which impacts its ability to perform. An engine misfire is caused by a disruption in the combustion process of the fuel. It’s important to take note of any strange sounds, power loss or engine knock that you may experience when driving, as these could be signs of an engine misfire.

Incomplete burning of the fuel during combustion can significantly affect the overall performance of the engine. This can result in noticeable drops in vehicle performance, such as a decrease in acceleration and fuel economy.

The most common symptom of a faulty spark plug is a jerking sensation while driving. This is because the failing spark plug causes some cylinders to be weak or not fire at all. As a result, your vehicle will feel like it’s stumbling as it switches between running either too much on some cylinders or too little on other cylinders.

In addition to this jerking sensation, other warning signs include:

  • Rough idling: Difficulty maintaining a consistent engine idle speed could be due to poor spark plugs.
  • Check engine light: If your “check engine” light comes on, have your vehicle inspected right away.
  • Decreased fuel efficiency: Faulty spark plugs can cause an improper air-fuel mixture, resulting in decreased fuel efficiency.

If you think you may have a problem with your spark plugs, have your vehicle inspected by a professional technician right away. Ignoring symptoms such as these could lead to additional, costly repairs down the road.

Driving with Bad Spark Plugs: Is it a Good Idea?

If you are unlucky enough to drive with malfunctioning spark plugs, then you are in for several serious issues. Bad spark plugs can cause an array of problems ranging from minor inconveniences to potentially detrimental engine damage.

Misfires are one of the most common issues resulting from faulty spark plugs. An engine misfire occurs when the air-fuel mixture inside a cylinder does not ignite correctly, thus causing a disruption in the engine’s performance. Misfires appear as jerking and shaking of the car, often accompanied by engine noise.

Having bad spark plugs can also lead to hard starts, where the car requires more cranking than usual before it catches and starts. Delayed ignition is caused by a lack of initial spark and leads to consistent difficulty starting your car.

Any driver knows that one of the main benefits of owning a vehicle is the savings in gas money. Unfortunately, malfunctioning spark plugs can significantly reduce your engine’s efficiency causing it to consume more gas. In other words, you end up spending more money on fuel due to the substandard performance of your car’s engine.

Rough idling, coupled with occasional jerks and stutters, is another telltale sign that your spark plugs are worn out or else misbehaving. As soon as you notice these symptoms, you should check your spark plugs for any signs of wear and tear.

Finally, lack of acceleration, reduced power and sluggish overall performance are symptoms that might indicate a deeper mechanical problem stemming from bad spark plugs. If you are struggling to get your speed up quickly then there might be something wrong with the sparking process occurring within your vehicle.

    • Misfires: Disruptions in engines performance accompanied by shaking and jerking.
    • Hard start: Delayed ignition caused by lack of initial spark.
    • Gas Consumption: Poor engine efficiency leading to increased consumption.
    • Rough Idling: Unusual jerks and stutters during idle.
    • Lack of Acceleration: reduced power and sluggish overall performance.

Avoiding the Costly Consequences of Not Replacing Spark Plugs

It is important to keep up with regularly scheduled maintenance, especially concerning your vehicle’s spark plugs. If these crucial components are neglected, the consequences can be severe. And without prompt attention and care, they may begin to show signs of wear, causing a myriad of problems.

Misfires are the most common indicator that your spark plugs need to be replaced. When this occurs, the fuel in the cylinders is not completely burned due to the incomplete transfer of energy from the spark plug to the fuel. This unburned fuel then lingers in its cylinder and begins to corrode the walls.

Fouling of the plugs can also occur when your spark plug maintenance is neglected. Over time deposits will build up on or around the spark plug which hinders their performance and creates a gap between it and the head which can cause arcing. When arcing happens, it creates an unpredictable pattern of sparks that lead to misfires.

Increased fuel consumption is yet another sign that your vehicle’s spark plugs may need replacing soon. As these components become less efficient at transferring energy between them and the cylinders, your engine will need additional fuel to make up for it. This excess use of fuel causes a noticeable drop in gas mileage.

Rough engine performance, such as increased noise from under the hood, hesitations when accelerating or idling, and reduced power output can all be attributed to failing spark plugs. If you notice any of these issues, consult with a mechanic as soon as possible before any more permanent damage is done.

Replacement, although tedious and time-consuming, is still something that needs to be done promptly in order to ensure good engine health. New spark plugs will help restore optimum engine power and efficiency by burning more of the fuel entering each cylinder.

  • Replacing spark plugs regularly
  • Cleaning or swabbing faulty ones
  • Checking connections
  • Avoiding damage-causing deposits

These basic steps will go a long way toward preventing any potential harm arising from faulty spark plugs or clogged connections down the line.

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what happens when spark plugs go bad

Watch Out: These are the Symptoms of Bad Spark Plugs

Are you noticing strange noises, poor performance, and a sudden drop in fuel efficiency coming from your vehicle recently? It’s likely that your spark plugs could be to blame. The spark plugs in your engine produce an electric arc that ignites the fuel in each chamber for combustion. When these spark plugs don’t fire correctly, it can lead to serious car issues.

Reduced Gas Mileage: One of the most common signs of bad spark plugs is a decrease in fuel economy. If your car’s once reliable MPG drops substantially, this could be indication that your spark plugs need replaced. This drop in gas mileage is caused by the uneven combustion of fuel due to the faulty spark plug.

Lack of Acceleration: In addition to reduced fuel economy, another major symptom of bad spark plugs is a lack of acceleration when you press on the gas pedal. You can also experience missing and sputtering in your engine as you try to accelerate.

Hard Starts: If you’ve gone out to start your car only for it to take multiple tries for it to start up, this could be another indication that one or more of your spark plugs have died out. The failing ignition system means that the fuel isn’t ignited correctly and needs more time for combustion before it can start properly.

Engine Misfires: When you have bad spark plugs, your engine will have a difficult time completing its firing process. Rather than firing completely all at one time, you might notice that the engine is shaking or jumping when running due to misfires.

Rough Idling: If your engine is making loud knocking and pinging noises when idle, this could be a symptom of a worn-out or damaged spark plug. This occurs when there is a lack of power getting transferred through the plug during the electrical current sparks process.

If you spot any of these symptoms on your vehicle, then it’s worth bringing it into the shop. Replacing old or worn-out spark plugs should be brought back to optimal performance levels with better gas mileage and increased performance.

How Long Can You Put Up with Bad Spark Plugs?

The typical American puts 13,476 miles on their car annually, which translates to an average of 1.5-2.25 years for a set of spark plugs. With proper maintenance and attention, these can last longer – but how long do they last when neglected?

Neglected spark plugs won’t improve the performance of your engine. In fact, they could even cause major damage if they become too damaged or worn out. If the surface of your spark plug becomes corroded, or there’s any build up of oil or debris on the electrodes, your engine won’t be running as efficiently as it should. This can cause increased exhaust emissions, decrease fuel economy, and lead to poor engine performance altogether.

Additionally, ignoring bad spark plugs too long can lead to serious damage to other parts of the engine. Spark plugs ignite the air-fuel mixture in the cylinder chamber; if this spark isn’t strong enough and the mixture doesn’t combust properly, it can lead to a build-up of unburnt fuel in the engine. This extra fuel will eventually burn out important components of the engine like ignition coils and pistons.

So how do you know when your spark plugs are failing? Here are some common signs:

      • Misfiring – When your spark plugs fail, they won’t be able to produce sparks quickly enough or with enough intensity to ignite the fuel. When this happens, you may notice a jolt or jerking motion when accelerating.
      • Decreased MPG – If your spark plug misfires often enough, it will have an effect on your fuel economy. Increasingly poor MPG is one sure sign that something isn’t functioning correctly.
      • Rough idle – When you’re at a standstill in traffic with no acceleration needed from you, if your car struggles to stay at an even idle RPM that’s a sign that something may need replacing soon.

To ensure that your vehicle is running smoothly and efficiently for as long as possible, it’s important to stay on top of regular maintenance including changing the spark plugs regularly. Neglected spark plugs can be dangerous for both you and your engine – so make sure you pay attention to any warning signs!

What Does a Bad Spark Plug Sound Like?

Bad spark plugs can make a distinctive, knocking sound when accelerating your vehicle. This sound is caused by something called misfiring, when the spark plugs do not ignite all the fuel completely. The fuel and vapor that don’t ignite will eventually catch fire and detonate.

Misfiring happens due to an improper spark from the spark plug, or a weak spark. This can occur if the spark plug is worn out or was installed incorrectly. It can also happen if there isn’t enough air or fuel getting to the spark plug.

When you hear this knocking sound coming from your engine, it’s important to diagnose it right away and find out what is causing it. To help identify if you have bad spark plugs, here are some other signs to watch for:

      • Chugging engine performance: You may feel a sudden drop in your vehicle’s acceleration when you press down on the gas pedal.
      • Decreased fuel efficiency: Your car may not be able to maintain its usual mileage as long as it used to.
      • Surging engine: You may notice a sudden surge of power, followed by barely any power at all.
      • Vibrations inside your cabin: You may feel a slight tremor in your steering wheel and shifter.

When you start noticing any of these signs, it’s time to take your car in for maintenance and have a mechanic check your spark plugs. Ignoring any of these symptoms could lead to more serious damage being done to your engine, which in turn will cost you more money.