Changed Spark Plugs And Coils Still Misfiring – How To Fix It?

Have you recently changed your spark plugs and coils only to find that your engine is still misfiring? If the answer is yes, then you’re not alone. It’s a common issue experienced by many car owners. And this frustrating scenario can leave you puzzled, especially if you’ve just replaced your spark plugs and coils.

In this article, we’ll explore the reasons behind the issue “Changed Spark Plugs And Coils Still Misfiring” and offer comprehensive solutions to get your vehicle running smoothly again.

We’ll dive deep into the heart of your vehicle, uncovering the mysteries of engine misfires and guiding you through the steps of resolving the problem.

Step No. Steps
1 Check for trouble codes using an OBD-II scanner.
2 Inspect spark plugs for fouling, damage, or wear.
3 Check ignition coils and wires for visible damage or loose connections.
4 Perform a compression test to assess engine health.
5 Check fuel injectors for clogs or malfunctions.
6 Determine if professional assistance is needed.

Understanding Spark Plugs and Coils

Changed Spark Plugs And Coils Still Misfiring

Before we delve into the potential causes of the misfiring problem, let’s get a good grasp of what spark plugs and coils are and the roles they play in the engine.

The Role of Spark Plugs in Igniting the Fuel in the Engine

Spark plugs are small, yet crucial components of your vehicle’s engine. They produce an electrical spark that ignites the fuel-air mixture in the combustion chamber of your engine.

This spark starts the combustion process, which ultimately drives the pistons in your engine and keeps your vehicle in motion. When spark plugs are in good condition, your engine will run smoothly.

However, when they become faulty or worn out, problems can occur. One common issue is engine misfiring, which can cause your vehicle to run poorly and potentially lead to more serious damage if not addressed promptly.

If you’re facing a situation where you’ve changed spark plugs and coils still misfiring occurring, the root of the problem may not necessarily lie within the spark plugs or coils.

It could be a symptom of a deeper underlying issue in your vehicle’s engine or ignition system. To get a better understanding of what might be causing this issue, let’s look at the function of ignition coils.

The Function of Ignition Coils in Generating the Spark

Ignition coils play a vital role in your vehicle’s ignition system. Their primary function is to generate the high voltage necessary to produce the spark that ignites the fuel-air mixture. They do this by converting the vehicle’s low voltage power into thousands of volts that a spark plug requires to create a spark.

If an ignition coil becomes faulty, the spark it produces can become weak or non-existent. This, in turn, affects the combustion process, leading to engine misfire. This is why it’s important to ensure that both your spark plugs and your ignition coils are functioning properly. Despite the spark plugs and coils replaced still misfire can happen due to multiple reasons.

Understanding the role of these components can help you troubleshoot potential issues when you face a problem like your car shaking after changing spark plugs. Here’s an article that can provide you with further insight into engine-related issues.

Importance of Using the Correct Spark Plug Type for Your Vehicle

When it comes to spark plugs, not all are created equal. Different vehicles require different types of spark plugs, so it’s crucial to use the correct type for your specific vehicle. If you don’t, it can lead to issues such as engine misfiring, even after you’ve changed the spark plugs and coils.

In some cases, even if you’ve replaced coil pack and spark plug still misfire can occur if the new spark plugs are not compatible with your vehicle. That’s why it’s crucial to always check the vehicle’s manual or consult with a professional mechanic to ensure you’re using the correct spark plugs.

Common Causes of Engine Misfiring

Now that we understand the roles of spark plugs and ignition coils let’s look at some of the common causes of engine misfiring, even after these components have been replaced. Knowing these causes will help you diagnose the problem correctly and take appropriate action.

1. Faulty Fuel Intake and Its Impact on Engine Misfiring

Fuel intake issues can be a common cause of engine misfiring. The engine requires the correct air-fuel mixture for optimal combustion. If the fuel intake is faulty, it can result in an incorrect air-fuel mixture, leading to inefficient combustion and, consequently, engine misfire.

Issues such as a faulty fuel pump, clogged fuel injectors, or problems with the fuel pressure regulator can all lead to fuel intake issues. If you’ve changed spark plugs and coils still misfiring, you might want to check the condition of your fuel intake system. This link provides additional information on how a faulty fuel intake system can affect your engine’s performance.

2. Build-up of Oil or Debris on Spark Plugs Leading to Misfire

Even new spark plugs can become dirty or oily due to issues within the engine. This can occur due to a leaking valve cover gasket, which allows oil to seep into the spark plug tubes, or due to a rich air-fuel mixture, which can cause soot to build up on the spark plugs.

If the spark plugs are dirty or oily, they will not be able to produce a strong enough spark to ignite the fuel-air mixture properly, resulting in engine misfire. Therefore, even after you’ve changed spark plugs and coils still misfiring can occur if there’s a build-up of oil or debris on the spark plugs. You can find more details on this topic in this article.

3. Damaged or Loose Spark Plug Wires Causing Misfiring

Spark plug wires carry the high voltage from the ignition coil to the spark plug. If these wires are damaged, worn out, or not connected correctly, they can cause engine misfire. This is because the electrical current will not reach the spark plug effectively, resulting in a weak or non-existent spark.

If your car shakes when idling but not in neutral after you’ve changed the spark plugs and coils, you might want to inspect the spark plug wires for any signs of damage or incorrect installation. This guide can help you understand more about this issue.

4. Other Potential Factors such as Engine Cleanliness and Oil Pressure

There are several other potential factors that can cause your engine to misfire, even after you’ve changed the spark plugs and coils. These include low oil pressure, issues with the engine timing, or problems with the engine control module (ECM).

Furthermore, the cleanliness of the engine can also play a role. If there’s a build-up of dirt or debris within the engine, it can affect the functioning of various components, including the spark plugs and coils. Therefore, regular engine cleaning and maintenance is essential for preventing engine misfire and other issues.

Changed Spark Plugs And Coils Still Misfiring – Diagnosis and Troubleshooting

If your engine is misfiring despite having new spark plugs and coils, you’ll need to do some troubleshooting to identify the root cause of the problem. Here is a step-by-step guide to diagnosing a spark plug misfire.

Step 1: Checking for Trouble Codes Using an OBD-II Scanner

The first step in diagnosing a misfire is to check for trouble codes using an

On-Board Diagnostics II (OBD-II) scanner. This device can read information from your vehicle’s computer system and reveal any diagnostic trouble codes (DTCs) that have been logged.

When your engine misfires, it’s likely that your vehicle’s computer system will log a misfire code. By checking this code, you can get an idea of which cylinder is misfiring and start your diagnosis from there. If you don’t have an OBD-II scanner, you can usually borrow one from a local auto parts store, or you can have a mechanic perform this check for you.

Step 2: Inspecting Spark Plugs for Fouling, Damage, or Wear

If your OBD-II scanner reveals a misfire code, the next step is to inspect the spark plugs in the misfiring cylinder. Even new spark plugs can become fouled or damaged, which can lead to a misfire.

You should look for signs of oil or soot build-up, check for any physical damage to the spark plug, and ensure that the spark plug is gapped correctly. If the spark plug is fouled or damaged, it will need to be cleaned or replaced.

Step 3: Checking Ignition Coils and Wires for Visible Damage or Loose Connections

Next, you should check the ignition coil and spark plug wire for the misfiring cylinder. Look for any signs of physical damage, such as cracks or burn marks, and ensure that the coil and wire are securely connected.

A damaged or loosely connected ignition coil or wire can lead to a weak spark, which can cause the engine to misfire. If you find any issues during your inspection, you will need to replace the faulty components.

Step 4: Performing a Compression Test to Assess Engine Health

A compression test can help you determine the health of your engine. It measures the pressure created by the engine during the compression stroke. If the compression test reveals low pressure in the misfiring cylinder, it could indicate a problem with the engine, such as a burnt valve or a blown head gasket.

Step 5: Checking Fuel Injectors for Clogs or Malfunctions

The last step in the diagnosis process is to check the fuel injectors. A clogged or malfunctioning fuel injector can cause a lean air-fuel mixture, leading to a misfire. You can check the fuel injectors by listening to them with a mechanic’s stethoscope or by using a fuel injector tester. If you find a problem with a fuel injector, it will need to be cleaned or replaced.

When to Consult a Mechanic for Professional Assistance

If you’ve gone through the above steps and are still experiencing misfires after you’ve changed spark plugs and coils still misfiring, it’s time to consult a professional mechanic. Some engine problems can be complex and require specialized tools and knowledge to diagnose and repair. It’s always better to seek professional help rather than risking further damage to your engine by trying to fix the problem yourself.

Prevention and Maintenance Tips

While it’s important to know how to troubleshoot engine misfires, prevention is always better than cure. Here are some tips to help prevent engine misfires and keep your ignition system in top shape.

Importance of Using Quality Parts When Replacing Spark Plugs

When it comes to spark plugs, quality matters. Cheap, low-quality spark plugs can wear out quickly and may not provide a reliable spark. Always opt for high-quality, reputable brands when buying spark plugs. This can help prevent engine misfires and improve the performance and longevity of your engine.

Keeping the Engine Clean and Well-Maintained

Keeping your engine clean and well-maintained is key to preventing engine problems, including misfires. Regularly check your engine for signs of

oil or soot build-up and clean it as necessary. Additionally, regular oil changes can help keep your engine running smoothly and prevent oil from fouling the spark plugs.

Regular Inspection and Maintenance of the Ignition System

Regular inspection and maintenance of the ignition system can also help prevent engine misfires. This includes checking the spark plugs and ignition coils for signs of wear or damage and replacing them as necessary.

Additionally, you should inspect the spark plug wires for any signs of damage or loose connections. If you notice any problems during your inspections, it’s important to address them promptly to prevent more serious issues from developing.

FAQs (Frequently Asked Questions)

Can new spark plugs cause misfire?

Indeed, new spark plugs can cause misfire if they are not correctly installed, are damaged, or are not the right type for your specific vehicle. Even after you’ve changed spark plugs and coils, misfiring can still occur. Always double-check the specifications and condition of your new spark plugs to prevent issues.

Why would spark plug misfire even after a change?

Misfiring even after changing spark plugs could be due to various reasons, including incorrect installation, damage during installation, or using incorrect spark plugs for your specific vehicle. Other factors like faulty fuel intake or damaged spark plug wires could also contribute to this problem. If the issue persists after the spark plug change, it’s advisable to seek professional assistance.

Should I switch to iridium spark plugs?

Iridium spark plugs are known for their longevity and performance. However, whether you should switch to iridium spark plugs depends on your vehicle’s requirements and your personal preferences. They can be more expensive, but if performance and durability are your priorities, iridium spark plugs could be a good choice. Always consult with your mechanic or refer to your vehicle’s manual for the best advice.

What are the symptoms of a misfiring engine?

The symptoms of a misfiring engine can include noticeable jerks or vibrations while the vehicle is running, reduced fuel efficiency, engine sounds like it’s sputtering or running unevenly, and the check engine light may come on.

For instance, your car shaking after changing spark plugs could be a symptom of a misfiring engine.

What causes ignition coil failure?

Ignition coil failure can be caused by various factors, including heat and vibration damage, wiring or connector damage, or faults with the spark plugs. Remember that a faulty ignition coil can lead to engine misfiring.

If you’ve changed spark plugs and coils but misfiring still occurs, the ignition coil could be the culprit.

How to prevent spark plug misfire?

Regular maintenance is key to prevent spark plug misfire. Ensure your spark plugs are the right type for your vehicle, properly installed, and changed regularly. Keeping the engine clean and well-maintained, along with regular inspection of the ignition system, can help prevent misfiring.

What if only one cylinder misfires?

If only one cylinder misfires, it could indicate a problem with the spark plug, fuel injector, or coil pack associated with that specific cylinder. A compression test can help diagnose if the problem lies with the cylinder itself.

How does the ignition system work?

The ignition system of a vehicle is responsible for igniting the fuel-air mixture in the engine’s combustion chamber. The key components of the ignition system include the battery, ignition coil, distributor, ignition module, and spark plugs.

In a fully functioning ignition system, the battery supplies power to the ignition coil, which transforms the low voltage into high voltage. This high voltage is then directed to the correct cylinder by the distributor, causing the spark plug to spark and ignite the fuel-air mixture.


Facing an engine misfire can be frustrating, especially after changing your spark plugs and coils. However, by understanding the potential causes and knowing how to troubleshoot the problem, you can get your vehicle back on track.

Remember, regular maintenance and the use of high-quality parts can go a long way in preventing engine misfires. If you’re ever unsure about diagnosing or fixing an issue, don’t hesitate to seek professional help. Your vehicle’s health is worth it.

I hope this guide on “Changed Spark Plugs And Coils Still Misfiring – What To Do Next” proves helpful. For more such guides and automotive advice, do visit the blog section of our website. Drive safe!

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