Have you started experiencing some bad spark plug symptoms and you are looking to learn what does a bad spark plug look like? Well, if that is the case, then you are at the right place because there will be a lot to cover on this topic.
Having a problem like this with the spark plugs can be really frustrating to deal with. Why I’m saying this? Well, because it is true. When spark plugs go bad, they will start to produce a ton of symptoms and your driving experience will not be that great. You will face a ton of struggles while attempting to drive a car like this.
This is why you need to learn how to read spark plugs. More precisely, you need to understand the spark plug fouling chart in order to be able to diagnose bad spark plugs on your car. Spark plugs can tell a lot of different stories and based on this input you should determine what could be causing these issues. And this is why we’re going to help you out.
First, we will learn what are spark plugs and the type of spark plugs. Then we will cover what is a fouled spark plug and the bad spark plug symptoms. After that, we will move on to learn the reasons why the spark plugs fail and how to read and diagnose spark plugs. So, if you want to learn more, follow along.
What Are Spark Plugs (And What Does A Bad Spark Plug Look Like)?
Now before we dive into more complex topics like what does a bad spark look like. Let’s first learn more about what are spark plugs in general. Knowing this will be really useful for you if you want to learn something new about mechanics and also to understand how these spark plugs work behind the curtain. So, keep up with us.
So, what are spark plugs? Well, spark plugs in simple words are electrodes. If you don’t know what is an electrode, in simple words an electrode is a component that is specifically designed to deliver high electrical current.
Which in our case is the spark plug. This spark plug consists of the terminal which is located at the top, and the insulator which is the white component. This insulator is usually made out of ceramics. Then there is the casing around the spark plug that you use to bolt on the spark plug.
And at the bottom, there are two electrodes. The central electrode, and the ground electrode that is overlapping the central electrode. And between these two electrodes, all the magic happens in creating the spark and igniting the air to fuel mixture in the cylinder.
Without a spark plug, you will not be able to run the engine since the fuel will not get ignited. So, you understand why the spark plug is such an important component in your vehicle.
Most engines are using a single spark plug system but there are also some engines that are running two of these spark plugs per cylinder. But what does a bad spark plug look like? We will get to that, first let’s learn more about the types of spark plugs.
Types Of Spark Plugs
Now before we dive into the topic of what does a bad spark plug look like. Let’s first learn more about the types of spark plugs that are out there. Knowing this will be a good help for you to determine what type of spark plugs you need. So, what are the different types?
The first type of spark plugs that we are going to cover is the copper spark plugs. These are the original spark plugs in which the core is copper. These spark plugs work the best on older cars that are produced before 1980. The drawback is that they require more voltage to work and also they do not last a long time.
The second type of spark plug is the iridium spark plugs. These spark plugs are a good alternative to copper spark plugs because they offer better performance. They require less voltage and they last the longest of all the spark plugs. And are definitely a good alternative to copper ones. But they are slightly more expensive.
The third type of spark plug is the platinum spark plugs. These spark plugs are similar to copper spark plugs. Platinum spark plugs are better than copper but worse than iridium spark plugs. Still, they outperform the copper ones by a big margin. And also they collect less debris on them since they heat up a lot.
There is also a double platinum type. This type is really good if you have a waste spark distributor system. This system fires up the spark plug twice. It is not recommended to be used on modern vehicles. Overall, these are the types. But what does a bad spark plug look like? More on that in a bit.
Bad Spark Plug Symptoms
Now let’s get into the spark plug symptoms. This is an important aspect that we need to cover before we start learning more about what does a bad spark plug look like. Why is this the case?
Well, because every component when it goes bad, starts to produce different symptoms. And so is the case with the spark plugs. This is why you need to learn them to better understand when a spark plug is bad. So, let’s get into it.
1. Check Engine Light
The first symptom that we are going to cover before we learn what does a bad spark plug look like is the check engine light. But why is this the case? What has the check engine light has to do with the spark plugs?
Well, it has a lot to do with the spark plugs. This is the case because modern cars have a ton of sensors and they can start reporting problems to the PCM. And when spark plugs are going bad, there will be alarms that’s for sure.
More precisely, trouble codes are triggered by engine misfires. So, when you have bad spark plugs, don’t be surprised if you get a P0300 or a similar code that indicates misfires in the cylinder caused by bad spark plugs. Now let’s cover the next symptom before we learn what does a bad spark plug look like.
2. Car Struggles To Start
Now let’s cover the second symptom before we learn what does a bad spark plug look like and that is the situation when the car struggles to start.
If your car doesn’t start from the first try, checking the spark plugs should be one of your top priorities. A good car with properly working spark plugs should start immediately from the first crank.
Normally, we talk about cars with electronic ignition. So, if your car doesn’t like to start when you tell it so. Check the spark plugs. But what does a bad spark plug look like? We will cover that in a bit after we finish all of the symptoms of bad spark plugs.
3. Engine Misfires
The third symptom that we would like to cover before we learn what does a bad spark plug look like are the engine misfires.
As we mentioned in one of the previous chapters. Whenever the spark plugs are bad the car will love to misfire. These misfires will be represented by ticks coming from the top of the engine and the engine shaking a little bit.
Also, there will be pops from the exhaust and the flow of the exhaust gases will not be ideal. So, whenever you notice something like this. It could mean that you are having bad spark plugs in your car and these spark plugs need to be checked accordingly.
There are also other things that could make your engine misfire. But the spark plugs are the biggest cause of this type of reaction inside the engine. Now let’s move on to the next symptom before we learn what does a bad spark plug look like.
4. Rough Idle
The next symptom that we would like to cover when it comes to a bad spark plug before we learn what does a bad spark plug look like is the rough engine idle.
Whenever you have bad spark plugs, the car will definitely idle very poorly. You will notice how the RPMs are not stable.
A good stable RPM should be at about 800. If the RPMs are fluctuating this could mean that you have bad spark plugs in your car.
You need to be aware of these symptoms and determine if the spark plugs are bad. But for this, you need to learn what does a bad spark plug look like. And more on this we are going to cover in the following chapters after we finish with the bad spark plug symptoms. Now let’s move to the next symptom.
5. Poor Acceleration
The next symptom that we would like to cover before we learn what does a bad spark plug look like is the symptom when you have poor acceleration. So, why is this the case? Why the car would accelerate extremely poorly.
As you probably know, you need a spark to ignite the fuel. So, whenever you don’t have a constant spark inside of the cylinders, there will be a fuel that is not ignited. And if you have fuel that is not ignited, you have problems.
The car will perform poorly and will not deliver the horsepower numbers that it should deliver. So, the car will be really slow and will fail to deliver.
This could make you think that the engine is probably dying but you shouldn’t always jump to conclusions too quickly. Sometimes the problem is in the little things like the spark plugs and other ignition components. In order to solve this issue, you need to learn what does a bad spark plug look like. More on that we are going to cover later on in this article.
6. Poor Fuel Economy
And the last symptom that we are going to cover is the poor fuel economy. This is one of the most important symptoms that you need to beware of because even though you might not assume that the decrease is because of spark plugs. Actually, it could be the case. But why?
Well, if you don’t have enough spark inside of the cylinders the fuel is not igniting as it should and the engine doesn’t produce power.
So, the computer might be confused and think that it needs to add a bit more fuel to improve the combustion. So, it will drop more fuel and this fuel will basically ruin the spark plugs even more since the car will run rich.
The spark plugs will be covered in gas and this will even further going to prevent them from working as they should be working in the first place.
But what does a bad spark plug look like? Well, we will get to that after we cover all of the reasons why the spark plugs fail.
Reasons Why Spark Plugs Fail
Now let’s dive into the reasons why spark plugs fail before we start discussing what does a bad spark look like. So, what are the reasons? Why do spark plugs fail?
Well, there could be a number of things. You can get a fouled spark plug if your car is burning oil for example.
Cars love to burn oil, especially higher mileage vehicles that have oil rings on the pistons that do not seal particularly well. So, when this happens, the oil gets into the cylinders and covers the spark plug electrodes with oil.
The second most common reason for this situation is when there is a blown head gasket. When a head gasket is blown, the coolant will enter the combustion chamber and this will cover the spark plug electrodes with some white stuff once it evaporates. This will also cause the electrodes to fail.
The third most common cause of spark plug fouling is the air to fuel mixture. There are two conditions that are known. One of them is when the car runs lean. This is the case when the air to fuel mixture is more air than fuel. And the rich condition is when the air to fuel mixture is more fuel than air. This will cause the spark plugs to fail.
And the last way of failure is when the spark plug core simply gets worn out and disintegrates. This is also very common on copper spark plugs. So, beware of these things? But what does a bad spark plug look like? Well, that’s what we are going to cover next.
What Does A Bad Spark Plug Look Like
Now let’s see what does a bad spark plug look like? Let’s explain.
A fouled spark plug in many cases is not only visually identifiable. But more on the diagnostics, we are going to cover later on. For now, the most important things for us are the visuals.
A bad spark plug usually has some pitting on the central electrode. This is the main electrode that suffers the most and the one that gets the most damage.
So, if you notice how there is a chunk missing from the electrode when compared to a good spark plug it means that this spark plug is probably worn out.
Another thing to note is the color. If the spark plug is bad then this means that the car is burning oil in most cases. These carbon deposits on the electrode will prevent the electrode from working correctly. So, oil on spark plug is not something that you want to see on your car.
Similar case to when the head gasket is blown. The electrode will have white spots that are not good and could indicate that the spark plug is not good and doesn’t produce a good spark.
Another thing is the smell of gasoline. A spark plug that smells of gasoline means that this spark plug is probably not working very well and is not igniting the fuel.
And lastly, if there are blisters on the spark plug electrode and the electrode is orange to white, it means that there is a state of lean air to fuel mixture. There are more parts of air and too little fuel in the air-to-fuel mixture. Overall, this is what you need to know when it comes to what does a bad spark plug look like.
Spark Plug Diagnosis
Now as we learned what does a bad spark plug look like, we can move to other topics and learn more about the spark plug diagnosis. How you can diagnose a bad spark plug? Let’s explain.
Diagnosing a spark plug could be done by performing diagnostics with a multimeter. As you know, a multimeter is a tool that will allow you to measure resistance and other properties. But for our purpose, we are only interested in the resistance.
For this inspection, you need to tweak the multimeter to 20k ohms and then place one probe at the top terminal and one probe between the bottom two electrodes. Then check the reading.
A new spark plug should produce about 300 to 3000 ohms. A used spark plug should produce about 5000 ohms and a bad spark usually produces more than 5000 ohms. The more ohms, the worse the spark plug is in other words. For more details on how this is done, you can check the video that we attached above.
Spark Plugs Cost
So, we learned what does a bad spark plug look like. Now let’s learn how much does a spark plug cost in the first place? How much can you expect to pay for a new set of spark plugs?
Well, the average cost for a quality spark plug is about $10 to $15. So, if you have four of them you can expect to pay $60 to $80. If you have 8 spark plugs then you will pay more, about $160 to be more exact.
Conclusion To What Does A Bad Spark Plug Look Like
In this article, we have covered quite a bit when it comes to the topic of what does a bad spark plug look like.
First, we learned what are spark plugs and the types of spark plugs. Then we have covered the symptoms of bad spark plugs and how to read and diagnose the spark plugs. Then lastly we covered the costs involved in this spark plug replacement.
Now let’s answer some frequently asked questions.
What Do Spark Plugs Do
Spark plugs are components in the ignition system that deliver spark into the cylinders and help the air to fuel mixture to ignite. If the spark plugs do not work, the air to fuel mixture will not ignite and you will basically have a car that performs poorly.
How Long Do Spark Plugs Last
On average spark plugs last between 60,000 and 100,000 miles. Modern spark plugs tend to foul a lot less than spark plugs on older cars since the engines are much more perfected and it is really hard to ruin a spark plug on a modern car.
How Much Are Spark Plugs
Spark plugs are really cheap. You can get a set of four spark plugs for $40 or less if you get a good deal. So, this is why you should not be afraid to replace them when the time has come. Replacing them is a perfect beginner’s job when it comes to cars.
What Does A Bad Lawn Mower Spark Plug Look Like
A bad lawn mover spark plug is usually black if the lawn mover runs to love rich. And this is the situation with these small-displacement engines. They tend to foul the spark plugs. So, cleaning the electrode every once in a while might be a good idea when it comes to these engines.
How To Check Spark Plugs
In order to check spark plugs, first, you need to remove them. Remove the plastic cover and then unplug the ignition coils or wires. Then get a socket wrench based on the spark plug size and remove the spark plug. Then inspect it for possible damage on the electrode.
How To Tell If A Spark Plug Is Bad
You can tell if a spark plug is bad if you inspect the electrode. If the electrode is worn out and is all black then probably this spark plug needs to be changed. Also, measure the resistance of the spark plug with a multimeter. A good spark plug should produce about 5000 ohms.
How Long Does It Take To Change Spark Plugs
Replacing spark plugs usually takes not more than half an hour if you are experienced. If you are still getting into cars then it will probably take you one or two hours to get them replaced. You don’t need to hurry.
These tools have been tried and tested by our team, they are ideal for fixing your car at home.