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How to fix a misfiring engine

Do you hear your engine sputtering and coughing as you drive down the highway? Is it hard to climb steep hills in an otherwise well-behaved car? If so, then chances are your car is experiencing a misfiring engine.

Don’t worry, though: fixing this problem is not impossible. By following the steps outlined in this blog post on how to fix a misfiring engine, even novice mechanics can find success! Whether your issue lies within the spark plugs or fuel lines – we’re here to help walk you through that process and get back up and running without too much effort. Let’s get started now!

Tools you will need:

In order to diagnose and repair an engine misfire issue, you will need a few basic tools. These include:

  • Compression gauge
  • Spark plug socket
  • Spark plug gap tool
  • Timing light
  • Feeler gauges
  • Head gasket kit

How To Fix A Misfiring Engine Step-By-Step

If you’re experiencing a misfiring engine, it’s important to address the issue as soon as possible to prevent further damage to your vehicle. Fortunately, there are several effective ways to fix a misfiring engine, and I’ll share them with you now. Without further ado, let’s get right to it.

1. Check the spark plugs and wires

One of the easiest places to start is by checking for loose or damaged spark plug wires and worn out spark plugs. These are key components in ensuring your engine is running smoothly, so if they’re not performing correctly it could be causing a misfire.

– When your spark plug looks black or carbon fouled, it’s a sign that the engine was running too rich with too much fuel.

– If the plug is wet with gasoline or oil, you may have an issue with the fuel regulator or other more serious problems inside the engine.

– But if the spark plug appears to be undamaged, your next step should be to carefully check the gap between the metal section at its end and the base. This needs to closely match whatever it says on your car manual, otherwise it could be preventing correct air-fuel mixture from firing up.

– To ensure good electrical delivery from the ignition coil to the spark plug, don’t forget to replace its wire too.

2. Use a multimeter to test your coil pack

1. A multi-meter can help you ascertain whether your coil pack is in need of replacement. If your spark plugs are not sparking properly, it’s likely because something’s wrong with the current being sent out by the coil pack. With a diagnostic code identifying an issue doesn’t always narrow down the specifics, which is why this simple multimeter test can be so invaluable in helping you determine what needs to be fixed and replaced.

  • By disconnecting the spark plug wires and connecting an ohmmeter to the top two pins, you can get a reading on what resistance your specific vehicle should have and cross-check if that’s what you’re getting. Replace the coil pack if they don’t match up!
  • To begin, refer to your vehicle’s repair manual to find the right resistance rating. You can then easily identify the coil packs by running your hands along the spark plug wires moving away from the plugs.
  • If it’s determined that a coil needs replacing, all you need to do is disconnect and unbolt it from its bracket, put in a new coil, and reconnect it in the same manner as the old one.

3. Use a multimeter to test your coil pack

If the air, fuel, and spark look to be in order, then it’s time for a compression test.

Begin by finding the fuse that powers the fuel pump using the owner’s manual – then take out one of the spark plugs and attach the compression gauge firmly into place. Turn on the key and let the engine turn over four times. Once finished, compare your reading on the gauge to determine if it reached its highest point!


4. If air, fuel, and spark seem to be in order, do a compression test

Checking for compression can save you some time if you’re trying to diagnose a misfire in your engine. To check for compression, remove each spark plug from the cylinders and place a compression gauge over the cylinder. Turn on the engine and make several passes around the cylinders, recording each number.

Repeat this process for each one, making sure to reinsert the spark plugs after you remove the gauge every time. If all of the readings are similar except one, this suggests that there is an issue with compression in that cylinder.

However, if all of the numbers are roughly equal, then the problem isn’t related to this factor. If there are problematic cylinders near each other, it may be indicative of a faulty head gasket. In this case you’ll have to have your cylinder head removed from the engine in order to replace it.


5. Replacing a Blown Head Gasket to Address Engine Misfires in Adjacent Cylinders

If you’re experiencing an engine misfire in two nearby cylinders, it’s very likely due to a blown head gasket. You’ll need to replace your head gasket if that’s the case. There are other signs, such as coolant appearing in your oil, bluish exhaust smoke and noticeable oil leaks from where the cylinder head of the engine and the block meet. These clues can help shed light on whether or not you need to replace your head gasket.


6. Rebuilding the Bottom End of Your Engine to Fix Misfires Caused by Low Compression

If you’re dealing with an engine misfire, your saving grace is often the bottom end of your engine, where you’ll find most components that can be rebuilt. Checking for a lack of compression is a great place to start if this problem arises, as it may be due to failed piston rings, damaged cylinders or connecting rods.

In more severe cases, spark plug’s covered in oil are an indicator that the piston rings have broken down and are allowing oil to seep past the cylinder and shrink compression levels below what they should be – resulting in a misfire.


What is an engine misfire?

An engine misfire can be a serious issue for any vehicle, meaning it’s essential to identify the problem in order to fix it as quickly and cost-effectively as possible. While there are several potential causes for an engine misfire, from clogged fuel injectors and faulty oxygen sensors to fouled spark plugs, identifying the specific reason is essential to get your car running again.

Taking your vehicle for a diagnostic test is the best way to get a clearer indication of why it’s misfiring, so you can feel confident that you’ll get back on the road safely and swiftly.


What causes an engine to misfire?

Car engines can be extremely finicky, and when something as small as a spark plug goes wrong, it can cause even experienced drivers to break out in a cold sweat. Spark plugs are essential components of an engine – without them, it wouldn’t start.

That’s why understanding the most common causes of engine misfires is so important for car owners, who should always check for worn or improperly installed spark plugs, malfunctioning ignition coils, carbon tracking, faulty spark plug wires and vacuum leaks.

Related: Bad Spark Plug Symptoms

Symptoms Of A Misfire

How to fix a misfiring engine 2
How to fix a misfiring engine 2

A misfiring engine can be one of the most frustrating and potentially dangerous problems you’ll run into. The symptoms of a misfire vary depending on its underlying cause, here are the most common signs of a misfire:


Black Exhaust and Unusual Smells

When you take your car for a spin, the last thing you want is for rolling clouds of black exhaust to come out of your vehicle. Not only is that a sure sign of an engine misfire, but it can often lead to unhealthy air quality if left unchecked.

Keep an eye and ear out while driving; unusual smells, such as burning rubber, and big plumes of smoke are also telltale signs that something is wrong under the hood.


Rough Idling

Are you experiencing rough idling while driving? If so, it may be because your engine is misfiring. It is possible when the air to fuel mixture in the cylinder has been compromised that the engine will start and stop suddenly, resulting in a bumpy ride.

Furthermore, you may also notice a smell of fuel in your vehicle’s cabin – this could either be coming from outside or from the misfiring engine itself.


Sluggish Acceleration

Symptoms of a misfire can cause drastic issues with your vehicle’s acceleration. If you find yourself having difficulty reaching an adequate speed, or perhaps even experience jerking motions when attempting to accelerate, it is likely that your car is suffering from a misfire. When this occurs, it could be putting you and other drivers at risk on the road.

Therefore, it is important to diagnose and troubleshoot these sluggish acceleration issues as soon as possible for the safety of everyone involved.


Engine Sound Changes

Symptoms of a misfire can be very subtle and come in the form of changes you hear when starting your engine. Have you ever heard clanking, coughing, or sputtering? These could be signs that something is wrong with your engine and require further inspection.

If your vehicle is producing anything other than a smooth-running sound, it’s time to take it to a certified mechanic who will be able to diagnose it correctly.


Check Engine Light (CEL) illuminated on your dashboard

If you find that your “check engine” light has come on, it could be an indication that your engine is misfiring. Thankfully, many modern cars are equipped with sophisticated sensors that can detect when something is not working correctly under the hood.

While they may not be able to pinpoint an exact malfunction, they will alert you when a deeper investigation of the engine is necessary. As soon as the light illuminates, it’s important to talk to a qualified mechanic who can run tests and identify the root cause of the misfire.

How much does it cost to fix an engine misfire?

The cost of fixing an engine misfire depends on the underlying cause, as well as the type and age of your vehicle. Spark plugs are usually relatively inexpensive to replace, and can be done for around $50–$100 per spark plug.

Ignition coils can cost between $150–$1500 each, depending on the make and model of your vehicle. However, if a deeper problem such as a vacuum leak or damaged fuel injector is causing your engine to misfire, it could cost several hundred dollars to repair.

To be more specific, here are the average costs of some common causes of engine misfires that require repair:

  • Vacuum leak repair: $300–$900
  • Fuel injector replacement: $350–$600
  • Faulty ignition coil: $150–$250
  • Hole in the piston: $1000–$5000
  • Carbon or oil-fouled spark plugs: $100–$250

How to Avoid the Engine Misfire?

How to fix a misfiring engine 3
How to fix a misfiring engine 3

To avoid an engine misfire, it is important to keep up with regular maintenance. Make sure that you change your spark plugs and oil filter as recommended by the manufacturer. Additionally, inspect your vehicle’s ignition system components for signs of wear or damage, and replace them when necessary.

It is also a good idea to have your mechanic check the fuel injectors during routine service visits. A clogged or faulty injector can cause an engine misfire that will require costly repairs if left unchecked.

Lastly, make sure that you are using the right type and quality of gasoline for your vehicle, as this can help prevent problems with the air-fuel mixture in the cylinders.

FAQs about How to fix a misfiring engine

Can low oil cause a misfire?

Yes, low oil levels can cause a misfire as it reduces the amount of lubrication within the engine. This can lead to increased friction and wear on moving parts, causing them to fail over time. If your engine runs low on oil frequently, it could lead to premature component failure and more costly repairs.

What are the common causes of a misfiring engine?

The most common causes of a misfire include spark plug or ignition coil failure, vacuum leaks, fuel injector problems, and worn piston rings. Depending on the age and condition of your vehicle, other problems such as a faulty fuel pump or clogged catalytic converter could be to blame.

Can an engine misfire cause damage?

Yes, if left unrepaired for too long, an engine misfire can cause permanent engine damage. It can also put extra strain on the rest of the components, leading to increased wear and tear.

Is it okay to drive a car with a misfire?

No, it is not recommended to drive a car with an engine misfire. Driving an engine that is misfiring can cause increased wear on the cylinders and pistons, as well as other components in the engine. It can also cause a buildup of unburned fuel, which can damage the catalytic converter.

Can a misfire go away by itself?

No, a misfire is usually caused by an underlying issue in the engine and will not go away on its own. It is important to diagnose and repair the root cause of the problem as soon as possible to avoid more costly damage down the line.

Why is my car misfiring when I accelerate?

A car misfiring when accelerating may be caused by a faulty spark plug, ignition coil, or fuel injector. If your car is jerking when idling, it could be due to low oil levels, vacuum leaks, or an issue with the idle air control valve.

Why is my car jerking when idling?

It could be a problem with my spark plugs, but more likely the culprit is a build-up of dirt and grime throughout the system. Your air filter or fuel injection might be clogged, not letting enough fuel or oxygen get to the engine, causing it to shudder and jump.


How to fix a misfiring engine is a question on many drivers’ minds. Figuring out the root cause of the issue can be tricky, which is why it’s beneficial to enlist the help of a certified mechanic when needed. With their expertise and knowledge, they will provide insight into diagnosing and repairing the engine so that you can have your car running smoothly again.

Don’t forget that having the right tools or equipment to replace wear and tear parts are often essential in order to get the exact result you’re hoping for. If doing minor repairs still leave you with an unresolved misfire problem, getting professional assistance might be the best course of action. A certified mechanic will take care of all the necessary steps to guarantee a safe and reliable drive for yourself and other drivers on the road.

Timothy Ballard

I’m Timothy Ballard, owner of a used car dealership in Springfield. I love just about everything automotive, but I have a special place in my heart for trucks. I’m an ASE Certified Master Technician, so I know my way around a car. In my spare time, I enjoy traveling with my family and hiking new trails.

1 thought on “How to fix a misfiring engine”

  1. When experiencing an engine misfire, follow these steps to diagnose and resolve the issue:

    1/Check the cylinders: Start by inspecting each cylinder to determine if it is functioning properly.
    2/Diagnose the ignition: Identify any issues with the ignition system and address them accordingly.
    3/Check the ignition coil: Verify the condition of the ignition coil and replace if necessary.
    4/Check the fuel: Ensure that the fuel supply is adequate and free from contamination.
    5/Check compression pressures: Measure the compression pressures in each cylinder to identify any abnormalities.
    6/Vacuum leak test: Conduct a thorough vacuum leak test to uncover potential leaks in the system.
    7/Check mechanical problems: Examine the system for any mechanical malfunctions that could be causing the misfire.


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