How to Fix a Misfire? The Easy Fixes!

Naomi O'Colman

how to fix a misfire

how to fix a misfire

Do you know how to fix a misfire? When cylinders fail to generate power for your car, raw fuel may enter the catalytic converter, resulting in an engine misfire. Engine misfire is a severe ailment that should be addressed immediately to avoid costly repairs and a potential automobile fire. The longer you neglect it, the more serious the consequences will be.

What Is a Misfire in An Engine?

When the air and fuel ratio inside the combustion chamber of the car’s engine does not ignite correctly or at the right moment, it is called an engine misfire. It’s better to understand how your car’s internal combustion engine works to comprehend what a misfire is.

When the engine runs, your fuel injectors pour the correct amount of fuel into the combustion chamber. The air might also enter the chamber through your air intake system. The correct air/fuel ratio must be maintained for your car to run properly. Your ignition system will ignite precisely at the proper moment, creating a spark at the end of your spark plug. The air and fuel mixture is ignited, driving the piston into the cylinder. This procedure occurs thousands of times every minute in each of your car’s cylinders.

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When there is a misfire, the fuel does not ignite properly. It’s possible that the fuel never ignites, resulting in the cylinder never firing. The gasoline may also ignite too early or too late. These conditions result in a misfire, which causes your engine to operate poorly. If the problem worsens, your engine may stop working altogether.

What Causes Misfires in Engines?

Although this is not a comprehensive list of all possible causes of a misfire, they are the most common.

Here are the top three reasons:

#1 Defective Spark Plugs

In many cases, bad spark plugs are to blame for misfires. Spark plugs do not endure indefinitely and must be replaced when necessary. Spark plugs should be replaced every 50,000 to 100,000 miles in most cases.

When a spark plug fails, the combustion chamber no longer receives a suitable spark. The fuel will not ignite correctly without this spark. This will always result in a misfire. If numerous spark plugs fail simultaneously, your engine will operate poorly. Fortunately, spark plug replacement is not prohibitively expensive. In most automobiles, you can even replace the spark plugs yourself.

#2 Issues with the Ignition System

An issue with your ignition system, like defective spark plugs, will lack an appropriate spark. The spark may never reach the spark plugs. It’s also possible that the spark’s timing is off. Problems with the ignition system might range from bad ignition coil packs to a loose distributor cap. In addition, spark plug wires can potentially become faulty, preventing electrical current from reaching the spark plugs. A code reader can generally detect the problem with your ignition system in an auto repair shop.

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#3 Leak of Vacuum

Many vacuum hoses that control airflow to various engine components are routed around your intake manifold. These hoses require an excellent seal to correctly pull a vacuum and manage airflow. A leak in one of these hoses can completely disrupt the system. For example, it can cause a jerky idle, misfires, and other problems. A faulty or leaking manifold gasket can cause similar problems.

Other causes include:

#4 Fuel Injector Blockage

While many people assume that misfires are caused by difficulties with the spark or electrical system, misfires can also be caused by fuel issues. Fuel injectors that are clogged or unclean could also be the blame. Your engine will not be able to make a proper fire in the cylinder if the fuel delivery is not working properly. Rough idling, fault codes, and misfires can all be caused by buildup in the fuel injectors.

If you have dirty fuel injectors, start with a can of fuel system cleaner. This can be a low-cost and simple solution to the problem.

#5 Clogged Fuel Filter

Misfires are one of the issues that a filthy fuel filter can cause. Low fuel pressure can be caused by a clogged fuel filter, which prevents the necessary quantity of fuel from reaching the combustion chamber. This can cause power loss, cylinder misfires, and other issues. It could even wreak havoc on your gasoline pump.

While a fuel system cleanser may help, it’s more probable that the gasoline filter will need to be replaced. It’s a reasonably straightforward job that most vehicle repair shops can complete in two hours.

#6 Catalytic Converter

Engine misfires can be caused by a dirty or clogged catalytic converter, although this isn’t always the first indicator of a problem. When the converter blocks, the pressure in the exhaust system rises above the vehicle’s usual operating level. This can hinder exhaust gases from exiting the combustion chamber properly, resulting in misfires.

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Most of the time, the problems can be solved with a can of catalytic converter cleaning. However, you will need to repair severely blocked converters. A converter replacement is not cheap, as the part can cost upwards of $1,000.

#7 EGR Valve 

Many individuals are unfamiliar with how their car’s EGR valve works. Exhaust gases can recirculate via the manifold thanks to this valve. This reduces pollution and ensures that your vehicle runs smoothly. This valve, however, might become clogged and stop working correctly. In rare situations, your car may begin to run out of air as a result of this. If this is not addressed, the engine will misfire.

#8 Piston Rings That Have Been Worn

The pistons in the cylinders move up and down as the crankshaft spins. Pressure builds as the cylinder compresses the air inside the cylinder head. A proper seal along the cylinder wall is not created if the piston rings are damaged. Poor compression occurs because the pressure inside the cylinder cannot be maintained. Misfires and poor engine performance are caused by low compression.

A mechanic can conduct a short compression test to see if this is the source of your issues. A burst head gasket might cause similar symptoms, albeit you’ll most likely notice a mixing of oil and coolant in that scenario. Blown head gaskets also cause your car’s engine to overheat often.

#9 Computer Problems

As previously stated, your car’s engine contains numerous sensors connected to the vehicle’s main computer. Any flaws or issues with the sensors, computer, or software will cause significant problems. For example, an engine misfire might occur if the computer fails to transmit the necessary signal. All you need may be updated software for your car’s computer. In more serious circumstances, the computer may need to be replaced. Because replacing the computer module in your automobile might be pricey, you should get it done by a reputable mechanic.

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How to Recognize a Misfiring Engine

how to fix a misfire 2

Spark Plugs

A spark plug tester is useful since spark plug difficulties are among the most common reasons for engine misfire. A spark plug tester is low-cost equipment for checking whether your spark plugs are still in good operating order. Checking to see if the reason for the misfire is in your ignition saves time. It can also help you save time by pinpointing the problem.

Coil of Ignition

The ignition control module should be examined. Simply change out a questionable coil that may be causing a misfire in one cylinder for a quick examination. The ignition timing should also be checked. In some cases, the ignition timing is advanced, resulting in a misfire. Modern cars have timing sensors that can help owners figure out what’s causing the misfire. On the other hand, older cars feature a distributor for this purpose. Finally, simply inspect the cap for corrosion or carbon tracks that could be causing engine misfires.

Vacuum Leaks 

Using a spray bottle filled with water and dishwashing soap, locate leaks. Spray the vacuum lines, PCV valve, and intake manifold gasket with a cool engine. Start your car and keep an eye out for any bubbles. The hose is cracked if the RPM varies when you respray the same area.

How to Fix a Misfire

The difficulty in resolving the problem is determining the root cause. This manual will show you how to repair a misfiring engine. Before you go any further:

  1. Double-check that you have accurately diagnosed the car and identified the source of the misfiring.
  2. Always consult your owner’s handbook before tampering with your vehicle’s engine since doing so may cause more harm than good.
  3. Before you start, be sure you understand what you’re doing.
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Spark Plugs

If you’ve performed all of the following checks and determined that the spark plug is the problem, replacing it will cure the misfiring engine. This is the simplest and cheapest solution. They cost as little as $10 each and can be replaced in under an hour. It is advisable to replace all spark plugs at once to achieve consistent performance.

What is the average lifespan of a spark plug? Some spark plugs can now last up to 100,000 miles in service.

Wires for Spark Plugs

It would help if you also thought about getting new spark plug wires. It’ll be easy because you’ll be working in the same area and need to remove the wires to change the spark plugs. They are also reasonably priced. Spark plug wires range in price from $30 to $80. When it comes time to replace worn-out spark plugs, the wires are almost certainly due for repair.

Ignition Coils

Following the spark plug wires from the distributor will lead you to your ignition coil. Remove a few bolts and the electrical connector to pop it off. Depending on the age of your vehicle, you may have one or several coils. Coil to plug ignition failure will result in irregular misses and roughness. Spark plugs that are old and worn out are more prone to fail the ignition coil. In addition, a damaged catalytic converter or even the engine computer can be caused by a failed ignition coil.

Replacing an ignition coil in most 4-cylinder automobiles is straightforward. However, it might cost anywhere from $75 to $300. The cost of labor varies between $50 and $100 per hour. To avoid future issues, your mechanic may advise replacing all three rear ignition coils. You may replace them yourself at home, but be careful and detach your batteries first.

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Vacuum Leaks 

If you discover that your intake manifold gasket is failing, you can replace it yourself. However, before you begin, make sure you have intermediate knowledge and a repair manual.

What Is the Cost of Repairing an Engine Misfire?

The origin of the problem determines the cost of repairing a misfire. If you need to replace a single spark plug, you may be able to do it yourself for as little as $5. If you have more serious problems, such as a faulty ignition system or a clogged catalytic converter, you should expect to pay several hundred dollars for repairs. You must first thoroughly diagnose the problem before evaluating the repair cost.


A variety of issues can cause engine misfires, but the solution is typically straightforward. The problem is usually solved by replacing spark plugs or cleaning your fuel injectors. To deal with more sophisticated difficulties, you may require a scan tool to read the fault codes from your vehicle’s computer. The computer codes will provide you with a lot more information about the source of the problem. Your engine should continue to run smoothly once you’ve corrected it!