Problems After Changing Spark Plugs: What To Do? (Explained)

Changing spark plugs must be practiced very often because spark plugs affect so much of the vehicle in terms of performance and condition. However, many people are still experiencing some problems even after they have changed their spark plugs. So now, we will talk about changing spark plugs and some problems encountered after changing your spark plugs.

Your spark plug is essential. It is the one that is supplying spark that ignites the air or fuel mixture. By supplying the spark to produce ignition, it will create an explosion, and that will make your engine produce power. 

These plugs are creating an arc of electricity across the two leads. These leads are not touching, but both of them are close enough that the electricity can jump in between the gap. So with that, your spark plug contributes so much to your ignition system. 

This is why it’s crucial to always check them and replace them as often as necessary. If you wish to know more, stay and keep reading.

Problems After Changing Spark Plugs

What Problems Can You Experience After Changing Spark Plugs?

People will change their spark plugs because they notice some problems and slight differences in their vehicle’s condition and performance. But even after changing the spark plugs, some people are still noticing some problems. Here are some of the problems you can experience after you change your spark plugs.

Hard Start

After changing your spark plug, some people have complained that their car is having a hard time starting the engine or the car does not start at all. This can be because your spark plug is not working correctly.

Engine Noise

After changing your spark plugs, you might notice some rattling or some noises like knocking. If the spark plug is misfiring, you will hear these noises. It will come from your pistons and from the combustion that is not correctly working. 

The pistons need high velocities to travel, and if the spark plugs are misfiring, they will create these noises. These can be because of a faulty spark plug.

Poor Fuel Economy

You might notice that your fuel economy is still bad and is not improving. Spark plugs contribute a lot to a good fuel economy. If you have changed your spark plugs, you must notice that your fuel economy must be improving.

Reduction In Performance

You might notice that your performance is not reduced after changing your spark plugs. However, if you accelerate and change your gears, your spark plugs must be functioning at one hundred percent so that your engine will have optimum performance.

Why Does My Car Shake After I Changed The Spark Plugs?

Some people are complaining that their car is shaking after they have changed their spark plugs. There are a few reasons why your car is shaking. For example, you may have insufficient fuel pressures, or there can be misfires. 

However, if you have just recently changed your spark plugs and want to stick with the spark plugs, you might have faulty spark plugs or defective spark plugs. There can also be a faulty idle air control valve. It can cause your engine to idle to be below average.

problems when changing spark plugs

Can New Spark Plugs Cause Rough Idle?

Yes, your new spark plugs can cause a rough idle, but it is very unlikely. This is a new spark plug we are talking about. There can be some other reasons why your car is having a rough idle. 

But it is also not impossible that you still have failing spark plugs or defective spark plugs. If you want to have it checked by an expert, it is probably best to do that. There can be something wrong with the way you have changed your spark plugs.

What Should I Check After Changing Spark Plugs?

You must check if your engine is having a rough idle. If your spark plug is new, then you must not have a rough idle. You must also check if you will have trouble starting your car. 

Your new spark plug must not provide you any more problems with you starting your car. However, you should also check for any misfires in your engine. A faulty spark plug can cause a misfire in the engine. 

So you must check if your new spark plugs are not defective. In terms of the engine, you should also check if your engine is surging. Monitor also your fuel consumption. 

If you have a bad fuel economy, you must replace your spark plugs. If you have replaced your spark plugs and your fuel consumption is still high, there must be something with your spark plugs or other components in your car. Check also if your car’s performance has a low acceleration.

Should I Reset ECU After Changing Spark Plugs?

Some people are asking if they should reset their ECU after they have changed their spark plugs. Some people would say that you should not reset your ECU. Some people will also say that you don’t need to reset your ECU after you have changed your spark plugs. 

However, if you want to reset your ECU, some people will say it is not a very bad idea, but some would say there are no benefits. But if you will reset your ECU, you have to make sure that you are not on a new schedule for an inspection.

Can Spark Plugs Change Cause A Car Not To Start?

Yes, spark plugs can cause your car not to start. Many people are complaining that their cars will not start after they have changed their spark plugs. The fundamental problem is the ignition coils and the spark plugs.

Changed Spark Plugs Now Car Won’t Start: What To Do?

If you have changed your spark plugs and your car will not start, you have to check for any plug wires directly coming from the coil or the distributor and down into the plugs if they are attached firmly and correctly.  You can also check and get a diagram. 

Look for a picture of your car and look at how the wires are hooked up and connected. You might have attached the wires in the wrong way and the wrong places.


In summary, changing your spark plugs into a new one is very important. This is because spark plugs contribute so significantly to your vehicle’s performance and condition. 

However, some people are having problems even if they have changed their spark plugs. So you have to check your new spark plugs. Look for any defects and damages.

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Image credits – Canva

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My name is Hank, and I've been in the automotive industry for 27 years. I've been working in my own auto repair shop for the last 13 years, and now I want to help you here, on my blog. Let me know if you have any questions. Read more