How to Tell if Spark Plugs Need Replacing; 7 Proven Signs

Do you know how to tell if your spark plugs need replacing? This is a question that many car owners ask themselves, but few of them know the answer. Luckily for you, this article will give you some helpful tips on how to recognize when it’s time to change out those old spark plugs. These are important gadgets in your car, so, paying attention to their efficiency is key to a smooth running engine.

How to tell if spark plugs need replacing

Here are the crucial signs that you need to change spark plugs:

  • It is hard to start the car
  • Rough engine idle
  • Engine misfires
  • The electrodes are worn or rounded off
  • Poor acceleration
  • Poor fuel economy
  • Warning engine light

The role of spark plugs

Spark plugs are important parts of the ignition system of your car. They are responsible for igniting the air/fuel mixture in the cylinders. Once ignited, the pressure of that gas force pushes down on a piston and makes it move inside an engine block. The movement of this piston is what turns your car’s wheels to propel you forward. Having enough power for your car is one of the many benefits of changing spark plugs.

If you have worn-out spark plugs, your car will not be able to perform at its best. The main reason for this is that the spark plugs will not produce a stronger spark. Therefore, you will experience challenges with the car, for instance, it will take you long to start a car. In most cases, you will see people pushing a car to jumpstart it.

How often should spark plugs be replaced?

Most manufacturers recommend spark plugs to be replaced every 30,000 miles. This means that after 30,000 miles of using your car’s ignition system, it is time for you to change the old spark plugs. Before reaching this mileage mark, you should have noticed some signs that can help you recognize when it is time to replace those worn-out spark plugs.

The 30,000-mile mark was set based on manufacturers’ experience on how long it took for spark plugs to get wear out. This mileage figure is a ballpark figure that works for most drivers. However, there are some cars with engines more sensitive to spark plugs wear and damage than others. If you have such a car, it is important not to push your engine beyond its limit in terms of miles per year or before replacing the worn-out spark plugs.

7 signs to tell if spark plugs need replacing

1. It is hard to start the car

how to tell if spark plugs need replacing
Spark plug replacement

Spark plugs play a crucial role in starting your car. They have a very important job – igniting the air-fuel mixture in your engine. To do this, spark plugs need to produce an electrical charge which is strong enough for them to ignite that fuel. If you notice it’s hard for you to start your car or if the starting process takes longer than usual, there might be something wrong with spark plugs.

Some of the signs you will notice when you try to start the car include:

  • More cranks before the car starts
  • It’s hard to start your car when it is cold
  • The engine turns over but does not catch Spark plugs

If you notice these signs, it’s an indication that your car’s spark plugs need replacing. The earlier you do this the better for the performance of your car.

2. Rough engine idle

When your car is idling, it means that the engine is running and there are no other activities taking place. However, you might notice a rough or unsteady feel to the way your car’s engine runs when at idle. If this happens for more than half an hour, then one of the things causing such behavior is worn-out spark plugs.

To notice a rough idle, listen for signs like knock-like or rattling noise, pinging, or strong vibrations. If you hear any or all the above sounds, it is an indication that spark plugs may be having an issue that may need replacing.

3. Engine misfires

how to know if you should change spark plugs

When you step on the gas, your car should accelerate and run smoothly. There is no jerking or stalling of any kind because your car’s engine runs as one unit. If this does not happen, for instance, there are instances where the acceleration is delayed or takes place in intervals, then it might be a sign that spark plugs need replacing.

Engine misfires may be caused by oil on the tip of spark plugs. You should regularly check for the presence of oil on the tip of spark plugs. If you notice that the spark plugs have oil, it may be due to a cracked valve cover gasket, degradation of the spark plug O-ring, a faulty head gasket, or defective or worn valve guides. You will need to repair this as soon as possible as oil spills lead to engine misfiring. If left unattended for long, engine misfiring may damage the catalytic converter and this will cost you in excess of $1,000 to repair.

4. The electrodes are worn or rounded-off

If the spark plug’s electrodes are worn-out or rounded, the gap in between them widens. This means that the spark plug does not fire efficiently and it may produce a weak signal. When the electrodes do not form an arc, they cannot recover from this state to create another strong firing ability. If you notice such signs on your car’s spark plugs, then the problem with them is wearing out or rounding off of its electrodes.

If the spark plug does not fire efficiently, you will face challenges starting your car, especially in cold weather. Your battery will be drained in a bid to supply enough energy to power up the car. Consequently, battery life will be significantly reduced. Therefore, if you look at your spark plugs and notice that the electrodes are rounded-off, it is an indication that they need replacing.

5. Poor acceleration

Spark plugs play part in efficient acceleration. If your spark plugs need replacing, they may impact the acceleration rate of the car. You will notice that it takes longer to accelerate.

However, other factors like clogged or dirty fuel injectors, bad fuel filters, and ignition system may contribute to poor acceleration. Therefore, to be sure if the poor acceleration is due to worn-out spark plugs, you need to consult your mechanic.

6. Poor fuel economy

Poor fuel economy means that it takes too much fuel to get your car from point A to B. In such a situation, you will notice that there is no significant improvement in gas mileage after spending money on maintenance or repairs. If this happens, then the spark plugs may be worn-out or defective and need replacing.

Worn-out or dirty spark plugs reduces fuel economy because gasoline is not efficiently burned in the combustion cycle. Poor fuel economy means you will spend a lot on gasoline and you will be forced to make frequent trips to the filling station. Therefore, to be on the safer side, it is recommended to look for signs of worn-out spark plugs and replace them immediately.

7. Warning engine light

You should never ignore the “Check Engine”, “Malfunction” or engine silhouette lights. Most modern cars have a warning light that lets you know when the engine is misfiring and this may be due to worn-out spark plugs. If left unattended, these lights could indicate other problems like an ignition problem or defective fuel injectors.

If you notice one of such warnings after inspecting your car’s spark plug, then it is time to take your car in for a check-up.

Wrapping Up

Some drivers wonder how to tell if spark plugs need replacing. The answer is simple. You can look for signs like misfiring, engine light warning, or oil presence on the tip of your car’s spark plug and this may indicate worn-out or defective ignition plugs. The signs presented in this article are depicted by most cars when spark plugs are either dirty or worn out and need replacing. Therefore, if you notice any of these signs on your car, spark plugs may need replacing.

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