How to Fix a Misfire

Author

Javaughn Barrow

A cylinder misfire is when the combustion process within one or more of the cylinders in your engine fires incorrectly. Similar to a heartbeat your engine has a specific beat it has to make to work efficiently. Once a misfire happens you can think of it as skipping a beat. It’s very important to address any engine misfire issues as soon as possible as they can lead to extensive damage to your engine, which can be quite expensive. That being said, to fix a misfire we must first understand the basic firing operation of an engine (Combustion cycle) and what it takes for a misfire to occur.

What you will learn:

Understanding Engine Misfires

To better understand misfires let’s dive into when it goes right! When your engine is running correctly it goes through what we call a combustion cycle. There are 4 parts to a combustion cycle. S.S.B.B. This acronym stands for Suck, Squeeze, Bang, Blow. The engine’s piston moves down the cylinder sucking in an air-fuel mixture while the intake valves open. The intake valves then close while the piston moves back up the cylinder, Compressing the air-fuel mixture. When the piston reaches the top, a spark is ignited and combusts the pressurized air-fuel mixture pushing the piston back down again, for it to only return up pushing the exhaust from combustion out the cylinder when the exhaust valves open.

The part we want to focus on is the bang! When the piston squeezes the air-fuel mixture and the spark ignites, what happens after is called a power stroke. It takes the right amount of air, and fuel pressure for the spark to ignite the mixture, firing the piston downward. A misfire is when this concoction doesn’t ignite properly.  

Why Does My Engine Misfire?

You’re engine misfires because one or more of the components it takes to fire correctly is at fault for affecting the air, fuel, pressure, or spark for combustion. Because there are many possible causes for an engine misfire here are the general problem areas: 

• Ignition System
• Fuel System
• Mechanical Issues
• Vacuum Leaks

Common Causes of Engine Misfires

Ignition Issues

Faulty Spark plugs, ignition coils, distributor caps, and ignition wires are likely to cause an engine misfire. The spark needed for combustion is facilitated by all of these components. One or more of these components being faulty can fail to supply the right amount of electricity for the exact time needed for combustion, resulting in a misfire. 

When a fault is with the ignition system, it is usually accompanied by a check engine light. To properly diagnose and fix this issue you must first use a scan tool (OBD-2 reader) for engine diagnostics. Free scans are also available at your nearest AutoZone. The check engine light will have a code related to the issue and this code will confirm whether the issue is with the ignition system or not. After finding out what component may be faulty, the best course of action is to replace these parts with new quality manufacturer-recommended components. Common ignition system codes are: 

Storytime: I replaced my spark plugs and ignition coils to fix a cylinder misfire on my 2013 VW CC. One day I was driving when a flashing check engine light came on at the same time the car was hesitant to accelerate when I tried to. As soon as possible I took the car into VW and they started to diagnose the issue by using an OBD-2 scanner. If I remember correctly the code was a P0304, (One of the most common codes related to engine misfires) which means a misfire in cylinder number 4. The mechanic told me my spark plugs needed changing not only the one in cylinder 4. He also recommended changing out the ignition coils as well. I had bought this car with a weird maintenance history, so I took his recommendation changing out all the spark plugs and ignition coils. This fix the misfire issue and I never had an issue with these engine components again.

Fuel System Issues

Clogged or Faulty fuel injectors can cause the air-fuel mixture to be either too lean or too rich. Lean is where the mixture has too much air and not enough fuel and rich is too much fuel and not enough air. Since fuel is a key part of the air-fuel mixture, not having the right amount of fuel can cause pre-ignition or improper firing of the pistons. This will most likely cause a check engine light. Symptoms can include a rough idle, hesitation when accelerating, and higher-than-normal gas mileage. 

To diagnose and address fuel system issues, you must first use an OBD-2 scanner to pull any engine codes. Issues that concern the fuel system such as fuel injectors will most likely have a check engine light with a code. Once you have figured out the problem, replacing these parts could be complicated and pricey. At this point, you can reach out for professional help from your local mechanic. Replacing faulty fuel injectors may run you about $300 – $900 depending on make, model, and labor costs. In the case of clogged fuel injectors, you may want to try a cheaper option to unclog these components, by adding additives to a full tank of gas. Additives such as fuel injector cleaners. Fuel system engine codes are below. 

Mechanical Issues

Let’s talk hardware. Engine components such as Intake and Exhaust valves, Pistons, and Cylinders make up the combustion chamber. This is where combustion takes place. Each of these components has to be in excellent condition for proper combustion. Intake and exhaust valves getting damaged or stuck prohibit the combustion cycle’s proper seal, compression, and exhaust flow. These are all factors for a misfire to take place. Intake and exhaust valves provide an entrance seal and exit for the combustion cycle. The seal creates an environment for compression along with the piston and cylinders. The proper firing of the pistons is not only dependent on the air-fuel mixture but also on the components of the combustion chambers in good condition. 

If there are mechanical issues to this extent, it is most likely accompanied by a check engine light. From this point, you would then get an engine scan from an OBD-2 reader or a free scan from Autozone given that your car is drivable. If the engine has mechanical issues to this extent such as valves, pistons, or cylinder issues you should prohibit driving to avoid further damage. The engine scan will provide you with a code that points to the area of investigation. Engine maintenance or fixing to this extent can get complicated or expensive. It is recommended to reach out for professional help unless you know what you’re doing. 

Direct fuel injection engines are prone to carbon build-up which can create problems for the intake and exhaust valves. If this is your issue cleaning these valves by using valve cleaners may be your more cost-effective choice. Prices for valve cleaners ranging from $10-$100. However, these methods have been known not to do as effective a job as physically cleaning the parts which will be more expensive if paid for. 

Vacuum Leaks

Vacuum leaks refer to the airflow into the engine. Air flows through a series of hoses/pipes. If any of these pathways leak/not sealed will, unmetered air will make it into the cylinder. The consumption of gas will go up as the computer is trying to balance the system for the Air-fuel ratio parameters. Symptoms are rough idling and engine misfires as the quality and quantity of air is an important part of the air-fuel mixture for proper combustion. 

Tests for vacuum leaks involve blowing smoke through the pathways of intake air and monitoring where you see the smoke escape. Once the leak is found, be sure to replace or reseal any faulty or loose parts. Vacuum leaks can often come with check engine lights. Some check engine light codes that a vacuum leak can cause are: 

Diagnosing an Engine Misfire

When it comes to diagnosing an engine misfire one of the best routes is to use an OBD-2 Scanner. Because an engine misfire could be one or more of many engine components the OBD-2 scanner works perfectly in narrowing down the issue to specific problem areas. These types of engine scanners range in cost from $15-$50. You can also get a free engine scan from your local AutoZone. Engine misfires usually trigger a check engine light and this is where the OBD-2 scanner comes in handy. The scanner points you in the right direction of investigation. The check engine light comes with a code that the scanner will read. Each code refers to a specific area of the engine letting you know where the problem is.

Once you find out the problem you can begin to clean, fix, reseal, or replace any faulty loose, or dirty parts to get rid of an engine misfire. For issues more complicated than you can handle, it is recommended to reach out to your local mechanic for professional help. 

Helpful Tip: Getting a free scan from an autozone or by your means before you contact a professional mechanic can be very helpful. You are walking into the mechanic a more educated customer on the issue of your car rather than possibly being misled into expense. 

Preventive Measures and Maintenance

Regular Maintenance

Regular maintenance is one sure way to avoid engine misfires. Regular maintenance gives you a chance to replace old or worn fluids or parts that can potentially cause a misfire. It is highly recommended to follow the owner’s manual for regular maintenance cycles. 

Using Quality Parts and Fluids

When replacing parts or fluids it is good to spend an extra dollar to save a few more in the future. Good quality or recommended parts and fluids recommended in the owner’s manual are there for a reason. Your engine has been tested on these specific things for reliability purposes. Keeping up with the same recommendations is a good way to prevent any engine-related issues. 

Monitoring Performance

When driving your vehicle it is generally good to be aware of good performance. Getting a sense of how your vehicle is in good condition allows you to catch any early issues because you can recognize when something seems off. Not every little noise means that there is an issue but with enough driving time and experience, you can get a hang of knowing your vehicle’s performance. 

FAQ’s

1. What are the common symptoms of an engine misfire?

Common symptoms of an engine misfire are : 

• Rough idle
• Reduced fuel economy 
• Reduced engine power/performance  
• Check engine light 
• Unusual engine vibration 

2. Can a misfire cause damage to the engine?

Yes especially if left unaddressed. Engine components that facilitate the combustion cycle are at risk such as the pistons, cylinders, valves, and other components like the catalytic converter and o2 sensors. Continuous driving is not advised as it could lead to costly expenses. 

3. What are the main causes of a misfire?

The main causes are faulty components that are closely responsible for engine combustion. Components like spark plugs, ignition coils, fuel injectors, and the engine timing mechanisms. 

4. How can I diagnose a misfire in my engine?

A check engine light usually accompanies Engine Misfires. The perfect tool to diagnose would be an OBD-2 Scanner. You can buy one anywhere from $15-$50 with varying capabilities or get a free scan from your local Autozone. The OBD-2 port scanner provides a quick pathway to the engine’s problem area. Because there are many engine components, the engine computer will signal a problem in a specific area that the OBD-2 scanner can decipher, giving you a quick diagnosis and fix. One sure way to avoid engine misfires or to catch upcoming issues is to stay on top of the routine maintenance schedule for your vehicle.  

5. Is it safe to drive with an engine misfire?

While it is possible to drive with an engine misfire, it is not recommended. Reduced engine power is a symptom of an engine misfire and can make the vehicle unpredictable and unsafe when driving. It is best to deal with this issue as soon as possible to avoid costly repairs. 

Javaughn Barrow

Hello! My name is Javaughn Barrow, a young car enthusiast who writes all the articles for Karcandy.com. I’ve written over 50 articles about automobiles. With each article, I deepen my understanding and expertise in writing and the automotive world. Ever since childhood, I’ve always had a strong passion for cars. All types shapes and sizes were interesting to me. I’d spend most of my time after school researching cars and the more I found out about them the more exciting it was. In my teens, I created a fan page about corvettes posting content at least ten times a day! Yes, I was crazy about it. The page ended up garnering over 40k followers! After a while, I wanted more than a fan page. I wanted to express my passion differently. I wanted to create more helpful content, higher-quality content. My first car was a 2013 VW CC Sport. Learned very quickly car ownership wasn’t as expected. I spent a lot of time replacing control arms, cam position sensors, brake rotors, brake pads, etc. Walking away with more information than I knew before. As I was growing in my automotive journey I was learning about writing. Starting by writing a detailed outline about 300 words long then I would pay a professional to write a full 1000-word article and learn from them getting familiar with the process of writing. The moment I realized I could use my writing skills to express my passion for cars and help people simultaneously, I started Karcandy.com. I realized with my unique perspective coupled with my hard work discipline and work ethic I can create a space online to help bridge the gap between the complicated and simple in the automotive world. I’m motivated by the challenges and work it will take to create such a space. My work ethic is something I choose to refine and make better each day. I think it’s important to push myself and stay committed to my evolution as a human and this website is only one of the results of that.

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