10 Engine Misfire Symptoms You Should Be Aware Of

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engine misfire symptoms

Nothing really captures your attention quite like a sudden change in your car’s engine performance. A misfire can lead you to a headache and your engine to falter or drop RPMs for a brief period before regaining its usual performance. Typically, a misfire may reoccur during specified operating situations or at random times. Even If your engine is just sitting idle, a misfire may happen and can result in a rough or irregular idle.

Are you suffering engine stuttering, rough drives, lack of engine power, excessive smoke, strange engine sound and odor, check engine light, and other unusual engine behavior? These are frequent engine misfire symptoms, typically occurring whenever one or several of the parts required for combustion break from their exact and defined function. This might be due to an erroneous timing of spark plugs or an inappropriate air/fuel mixture ratio.

The most common engine misfire symptoms are:

  1. Engine power loss
  2. Rough idle
  3. Engine starting difficulty
  4. Poor acceleration
  5. Rough Acceleration
  6. Reduced Fuel Economy
  7. Increase in emissions
  8. Strange noise
  9. Unusual odor
  10. Check engine light

Engine misfire symptoms must not be disregarded, as a misfiring engine would perform poorly and can eventually cause engine harm, even if you are able to drive for a while. Additionally, your vehicle’s fuel efficiency can decrease, and emissions will increase as the engine is pushed to perform harder to adjust for the cylinder(s) which are not operating correctly.

In this article, we’ll be discussing the symptoms of a misfiring engine, as well as discover how engine misfire occurs, causes, and the cost of repairing a misfiring engine.

What Is an Engine Misfire?

A functional engine with four-stroke combustion burns fuel and generates power by performing a set of activities in the correct rhythm and time. Once the piston descends, it opens the intake valves, allowing a proper air/fuel mixture to reach the combustion chamber. Following the closure of the valves, this combination is compressed when the piston ascends.

Also, a spark plug ignites the air/fuel combination on the power stroke, significantly raising cylinder pressure. This enormous pressure rapidly compresses the piston, spinning the crankshaft in the cycle. On the exhaust stroke, the exhaust valve opens, releasing the cylinder’s burned gases. A fault produces misfires with the combustion components such as a spark, fuel and, oxygen or with one or more of the mechanical pieces in the engine, such as the cylinder.

Engine misfires may be caused by wrong timing or by one or more cylinders failing to execute all stages. When the air/fuel ratio is improper, the combination might not combust or will abruptly explode; a phenomenon is commonly known as engine knock.

Signs And Symptoms

Engine misfires, like numerous automotive issues, may exhibit similar symptoms. The first approach in troubleshooting the issue is to have the computer or electronic system scanned for codes. Below are the common and rare symptoms of an engine misfire.

Engine Power Loss

Curious what it feels like to drive with a misfiring engine?  There can be a noticeable power reduction due to the car operating with one or more cylinders functioning properly than expected, or there may be a temporary pause in the power transfer.

Additionally, you may experience recurring engine jerks, surging, or stalling. You’ll notice that acceleration is jerky or sluggish. Vibration is possible when the car runs, mainly when the engine misfire results from a mechanical issue. The intensity varies with RPM and is frequently greater at idle.

Rough Idle

In the majority of instances, this is the very first tell-tail indication that your car is having a fuel system misfire. Rather than a smooth idle, you’ll hear an intermittent fluttering noise and the changes in rev count. When your car seems rough while idling, do not disregard this indicator, this might be a symptom of bad spark plug, faulty distributor cap, or bad spark plug wirings.

If your misfiring issue worsens, the idle will become more jerky and irregular. Rough idling can be noticed instantly. Although some cases are milder than others, a car’s rough idle is often characterized by rocking and rattling. Additionally, you may detect strange noises and an irregular RPM.  Typically, a car’s smooth and continuous RPM rate must be approximately 1,000.

Engine Starting Difficulty

An engine misfire can occasionally result in trouble starting the car or stalling your engine while parked. Stalling occurs most frequently at idle yet may also occur when driving and could be very hazardous. Stalled engines are significantly more likely to happen when the engine is stressed by heavy accessory loads, like sitting at a stoplight having the air conditioner at full, headlights, and radio on with an extra loaded sound system.

Poor Acceleration

Engine misfires can affect your engine’s air/fuel mixture ratio. Whenever this occurs, it sends erroneous data not only to your Engine Control Unit (ECU), but also to other various components. The engine’s oxygen sensor is among these components. When your oxygen sensors provide misleading data due to an incorrect air/fuel mixture ratio, the vehicle’s computer will limit its acceleration. This sign can be more apparent in vehicles equipped with turbochargers. Such an engine will not get the required boost or air, resulting in a poor driving experience.

Rough Acceleration

Engine misfires can also result in rough acceleration. When driving, you might feel jerks and surges as the motor accelerates. This is the surest sign to determine a misfire.

Reduced Fuel Economy

Engine misfires can be generated by various ignition issues, including old or dirty spark plugs, faulty plug wires, defective ignition coil, or arcing across the plug wires or ignition coil and ground. Additionally, misfires can be produced by dirty or malfunctioning fuel injectors, intake manifold vacuum leaks, low fuel pressure, or intake manifold vacuum leaks. Misfire happens as a result of cylinder compression failure. All of these can trigger misfires and can result in excessive fuel consumption.

Emission Increase

Engine misfires can cause the engine to mix or burn the fuel ineffectively; you can observe excessive exhaust emissions. This can also happen if there are leaks creating compression difficulties, resulting in oil or coolant mixing with the combustion process.

Anything other than air/fuel mixture inside the combustion chamber will impair the engine’s capability to combust the mixture appropriately. Your exhaust fumes might be exceptionally dense or even blue-ish in color if burning oil is present throughout the combustion. Dark, toxic exhaust may suggest an excessively high air/fuel combination or carbon accumulation in the exhaust system.

Strange Noise

You may have difficulty identifying this symptom. The fact is that engines create a variety of noises. The V8 engine has a distinctive sound compared to a V6 or 4-cylinder engine. While your engine is misfiring in one cylinder or even more could completely shut down, converting your four-cylinder engine to a three- or two-cylinder configuration. An engine misfire noise is audible only to a skilled ear in most circumstances.

Unusual Odor

Defective cylinder walls can occasionally leak fluids, resulting in a mostly fuel with coolant or oil stench. Burnt coolant has a slight “pleasant” aroma. This one is more difficult to figure out since various types of misfires may result in multiple leaks that lead to various odors.

Check Engine Light

Check engine light can illuminate If your vehicle has a misfire due to a faulty fuel injector, low fuel pressure, bad spark plug, or other reasons. The check engine light is developed to alert you that there is a problem with the engine. Modern automobiles are built with an electronic control module, sometimes referred to as the vehicle computer. Your car’s multiple sensors will alert the computer when any engine component begins to fail.

The computer can determine the severity of the issue and, if it requires immediate care, it will illuminate the check engine light to warn the driver. Bear in mind that several other circumstances may potentially activate the check engine light. Once this light comes on, you’ll want to analyze your vehicle to determine the true reason for the issue.

Engine Misfire Causes and Solution

Numerous factors might contribute to engine misfire troubles. Your car engine relies on hundreds of components and systems to operate concurrently. Also, with exact timing to perform appropriately. Numerous issues may result in engine misfires. However, some happen more frequently than others.

Bad Spark Plugs

Spark plugs fire up your cylinders for the ignition of air/fuel mixture. A broken or faulty spark plug will produce a low spark or nothing at all. This implies that the air/fuel combination within the cylinder will not ignite correctly, resulting in an engine misfire.


The best option is to get a new spark plugs. Another method is to clean and inspect the electrode gap if your spark plug is in excellent condition.

Failing Ignition Coils

Ignition coils convert the vehicle’s low voltage electrical system to high voltage. Spark plugs need a high voltage to generate a strong spark. When it’s about misfires, the ignition coil is by far the most often encountered issue. Certain automobiles have a separate ignition coil for every spark plug, while others have a single coil attached to each plug by a sparking wire.


Replacement of the damaged ignition coil, maybe one or more. It is not required to replace all of them if just one is defective. Utilizing an OBD scanner device is recommended for this step since it will provide you with a code for the specific coil that has failed.

Damaged Ignition Coil Connections

It’s recommended to inspect the plastic connections atop your ignition coils. They may become brittle, shatter, and gradually lose contact due to repeated exposure to car engine temperature. Another frequent cause is an accumulation of dirt and corrosion within the connection.


The connection should be disconnected from your ignition coil and cleaned completely using a contact spray. Whenever the connection is significantly damaged, it must be entirely replaced.


While inspecting the connections, a quick examination of the wiring system going to your ignition coils is a great idea. While the harnesses and wires are well protected, they are also subjected to a continuous temperature of the engine, which could cause them to become brittle.

Although this is an uncommon occurrence, it does occur, particularly on older vehicles. Additionally, it’s a good idea to inspect the wiring setup of any additional parts that might be causing the engine to misfire.


Remove the existing wire or wires and exchange them with newer ones. Soldering the replacement connection is desirable for improved connection and the repair’s lifespan. However, this error may create more difficulties in locating the specific broken wire than repairing it.

Failing Fuel Injectors

Your car’s fuel injection system responsible for pumping fuel through the engine’s cylinder at high pressure. Even though they are constructed of very durable materials, delivering an explosive substance like gasoline at high pressure may eventually harm the injectors. Rather than creating a thin mist, they begin pumping a continuous fuel flow.


Replacement or refurbishment of the problematic injector or all of them is a wise step.  While it is a basic practice to repair or rebuild just the damaged fuel injector, it is preferable to examine all of them.

Malfunctioning Engine Control Unit (ECU)

A malfunctioning ECU that results in misfires is very unusual. If this occurs, it is almost often the result of an electrical overloading or external damages like mistakingly switching the battery terminals, defective alternator delivering overly high voltage, short circuits, incorrectly jump-starting the automobile, etc.


Entirely replace or fix the ECU unit if possible. Purchasing a new one is too costly for most automobiles, which is why numerous people turn to technicians that specialize in ECU repair to solve the problem correctly. Once restored, the entire computer software system is required to be adequately reinstalled and configured properly.

Faulty Distributor Cap

This plastic-like cap that sits atop the distributor and connects the ignition lines. The majority of issues originate from material exhaustion. Over time, the central graphite and copper terminals connection will corrode. Another uncommon defect is a fracture in the cap.


Replace the cap

Vacuum Leaks

A vacuum leak occurs between the engine and the Mass Airflow Sensor (MAF). It makes the air/fuel mixture get thinner as more air is introduced into the system, resulting in the engine misfiring.

Ruptured or broken hoses, tubing, or boots, as well as unsecured clamps, are often the source of issues. In highly complicated circumstances, the issue might result from a defective brake booster, crankcase breather system, EGR valve, or PCV valve.


If the cause of the issue is the hoses, tubing, or boots, just replace the defective component. Replace and gently tighten any loose clamps. The more significant problem is locating the leak, which may be as little as a millimeter and in difficult-to-access areas.

Yet, there are methods and ways for finding a vacuum leak properly. However, an on-board diagnostic (OBD )scan should be conducted first for more significant disorders. When the source of the issue is identified, you may replace or fix the faulty component.

Intake Manifold Gasket Leak

Any leakage in the intake manifold could result in an incorrect air-fuel mixture ratio, resulting in the engine misfiring. Typically, the gasket joining the engine and manifold is the source of the issue. Additionally, another spot is between the manifold and the throttle body.


Replace your intake manifold gasket.

Bad Fuel Pump

The fuel pump is designed with an electric motor that delivers gasoline from the fuel tank to the engine in contemporary automobiles. When it fails, the gas supply could become insufficient or entirely stop. Most pump issues are triggered by material wear, specifically damaged pump bushings or brushes, rotors, or bearings.


Replace the whole pump assembly. The repair is relatively straightforward and inexpensive if your car’s pump is located externally. However, in many automobiles, the pump and the gauge transmitter are merged into a single plastic housing placed inside the gas tank. The pump may be changed independently of the casing and fuel gauge on some vehicles.

Low Fuel Pressure

Low fuel pressure might result from a faulty fuel pressure regulator, clogging fuel filter, or a damaged fuel pump—the engine’s low fuel pressure results in a lean fuel mixture, which causes misfires on every cylinder.


Replace your fuel pressure regulator

Clogged Fuel Filter

A dirty, contaminated, or clogged fuel filter will limit the volume of fuel supply and, consequently, the fuel pressure. These issues are caused mainly by low-quality fuel and poor car maintenance.


Replace your fuel filter

Low Compression

Compression is a critical aspect of the combustion process and the engine’s power production. Due to the inability of the air/fuel combination to circulate effectively in the cylinder, the engine’s low compression could result in an abruption in the combustion cycle.

With this indication, the misfiring isn’t as severe. It is often followed by additional symptoms such as the engine consuming or burning too much oil, producing insufficient power, and oil visible on the spark plugs. This is more common in older vehicles and those inadequately maintained cars.


To begin, determine the engine’s exact compression test result. A partial or overall engine rebuild is almost inevitable whenever one or more cylinders are depleted.

Engine Misfire Repair Cost

The spark plugs in our automobile is electronically timed to ignite at the exact moment set by the engine’s manufacturer. A misfire occurs when the spark ignites at the improper moment or does not ignite at all. Cylinder misfiring may occur for a variety of causes. The following are the most often occurring causes and associated expenses of the misfire situation:

• Corroded plug cables: $100 up to $300, depending on the price of replacement components and labor.

Spark plugs contaminated with carbon or oil: $100 up to $300, based on the price of the plugs plus labor to change them. Always remember (Bare in mind that carbon or oil-contaminated plugs are a symptom of a more serious engine issue, and diagnosing and repairing it will take more time & expense.

• Vacuum leak: from $100 up to $1,000, depending on the source of the leak.

• Incorrect fuel distribution: $100 up to $1000, depending on the origin of the issue: faulty injectors, broken intake manifold gaskets, replacement injector drivers, or Engine Control Module (ECM) reprogramming is required.

• Mechanical failures include a damaged valve spring, a scorched valve, a fractured or damaged piston, worn piston rings, and a damaged cylinder head gasket. This kind of repair may cost anywhere from $500 up to an outrageous five digits!


Therefore, develop the habit of doing routine car maintenance to avoid even one of these engine misfire symptoms from occurring. It can significantly increase the lifespan of your vehicle. Additionally, you can do regular car maintenance on your own. Furthermore, always maintain a consistent schedule specified in your owner’s handbook. Best of luck!


What does an engine misfire feel like?

Whenever a misfire happens, you can feel the engine producing a faint or powerful jolt. These misfires frequently occur if the engine is in strain, such as while accelerating rapidly. The most usual condition in which misfires are observed is when the engine is in a higher gear, but the RPM is lower, and the gas pedal is already touching the floor.

Can a misfire damage your engine?

A misfire in your engine may be caused by defective spark plugs or an unbalanced air/fuel combination. Running your car with a misfire is dangerous and can cause several engine damage.

What causes engine to misfire?

Several reasons cause a misfire, both rare and common. However, the most common reasons for misfires are often caused by old, incorrectly placed, and mismanaged spark plugs, defective ignition coils, graphite or carbon tracks, broken spark plug conductors, and vacuum leaks.

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