Common Weak Ignition Coil Symptoms You Should Be Aware Of

Have you ever felt like your car has a mind of its own? One moment, it’s purring smoothly; the next, it’s misfiring like an untamed beast. If these erratic episodes are becoming more frequent, chances are you’ve got a weak ignition coil on your hands.

Like these, several weak ignition coil symptoms can warn you before you end up in something more dangerous. For instance, engine stalling, vibrations, engine misfiring, and poor fuel economy are some of those common symptoms. 

If mystery surrounds you regarding these symptoms, it’s time to learn them in detail so that you can always remain warned. So, let’s move on. 

Why Does the Ignition Coil Become Weak?

A weak car ignition coil can be a frustrating and potentially dangerous problem for motorists. But Do Ignition Coils get weak with age? Is this a natural phenomenon? It’s natural, but not too soon. So, what causes this crucial component to become weak? Let’s explore the causes behind a weak ignition coil.

Age and Wear

Like any other part of your vehicle, ignition coils have a limited lifespan and will eventually degrade over time. Over time, the insulation materials deteriorate, leading to increased electrical resistance and decreased coil performance. Additionally, environmental factors like moisture, dirt, and contaminants can degrade the coil’s efficiency and weaken its output.

Voltage Spikes

Furthermore, voltage spikes from faulty wiring or improper installation can negatively impact the ignition coil’s integrity. These voltage surges put extra stress on the coil, causing it to weaken over time. 

Incorrect Spark Plug

Moreover, using incorrect spark plugs with inappropriate heat ranges can also result in a weak ignition coil by placing additional strain on the component.

Lack of Maintenance

Another aspect often overlooked is improper maintenance practices. Neglecting regular tune-ups and failing to replace worn-out components like spark plug wires can lead to increased resistance within the ignition system, thereby contributing to a weakened ignition coil.

Insufficient Power Supply

 An insufficient power supply from the battery or a malfunctioning charging system can result in a weak ignition coil. In such cases, the coil may not receive enough voltage to produce a strong spark consistently. 

Extreme Temperature Fluctuation

Frequent exposure to extreme temperature fluctuations can also affect the performance of an ignition coil. Prolonged operation under extremely high temperatures can cause internal degradation of materials and reduced overall efficiency.

Weak Ignition Coil Symptoms

Weak Ignition Coil Symptoms

As previously stated, when an ignition coil is weak, it typically results in some negative consequences or unusual activity in the car that serves as warning signs. 

However, some of these warning signs can be quite challenging to address, and there is a chance of interchanging with other component malfunctions. By accurately identifying these symptoms, you can quickly find effective solutions for repair. Below are some of the most prevalent signs that indicate a weak ignition coil.

Engine Misfiring

A misfiring engine can be a frustrating and alarming experience for any driver. Not only does it cause a loss in power and performance, but it can also lead to other costly issues if left unaddressed. A weak ignition coil is one of the most common causes of a misfiring engine.

When an ignition coil starts to weaken, it can no longer generate enough voltage to spark the fuel mixture in the engine’s cylinders consistently. This results in misfires or incomplete combustion, which can be felt as rough idling, hesitation, or stalling. Ignoring these symptoms can lead to further damage, such as fouled spark plugs and catalytic converter failure.

This problem is particularly challenging because it often goes unnoticed until it becomes more severe. Drivers may attribute the rough running to other issues like clogged fuel injectors or dirty air filters, not realizing that an underlying culprit could be a weak ignition coil.

Poor Fuel Economy

One of the most frustrating symptoms of a weak ignition coil is poor fuel economy. When the ignition coil fails to provide enough power to the spark plugs, combustion in the engine becomes inefficient. This results in wasted fuel and a decreased miles-per-gallon ratio. 

Aside from higher fuel costs, driving with a weak ignition coil means that your engine has to work harder and longer to achieve optimum performance. 

Over time, this strain can cause wear and tear on other engine components and even reduce the lifespan of your vehicle. If you notice a decrease in gas mileage without any apparent reason, it’s crucial to have your ignition system checked by a professional mechanic

Difficulty Starting the Vehicle

One of the symptoms of a weak ignition coil is difficulty starting the vehicle. When the ignition coil is not functioning properly, it can lead to insufficient electrical current being supplied to the spark plugs. As a result, you may experience delays or even complete failure in getting your engine started.

This difficulty in starting can manifest in various ways. Sometimes, you might notice that your engine cranks longer than usual before finally springing into action. Other times, you may have to make repeated attempts before the engine finally fires up. 

Engine Stalling or Dying

One of the most frustrating and potentially dangerous symptoms of a weak ignition coil is engine stalling or dying. Imagine navigating through busy city streets when your car’s engine suddenly cuts out, leaving you stranded in the middle of traffic. Not only does this put you at risk, but it also creates a potentially hazardous situation for other drivers on the road.

When an ignition coil starts to weaken, it may not be able to provide enough power to the spark plugs to keep the engine running smoothly. As a result, the engine may stall or completely die while driving. This can happen at any speed and under various conditions, making it all the more unpredictable and worrisome.

Decreased Power and Performance

When your ignition coil starts to weaken, you may notice a significant decrease in your vehicle’s overall power and performance. This is because the ignition coil plays a crucial role in providing the necessary electrical current to ignite the fuel mixture in the combustion chamber. A weak ignition coil can lead to incomplete combustion and a subsequent loss of power.

One of the first signs that your vehicle’s power and performance are being affected is a noticeable decrease in acceleration. You may find that it takes more time for your car to reach higher speeds or feel sluggish when you try to overtake other vehicles on the road. These symptoms all point toward a malfunctioning ignition coil that requires prompt attention.

Increased Emissions

One of the key symptoms of a weak ignition coil is increased emissions from the vehicle. The ignition coil generates the necessary voltage to ignite the fuel mixture in the combustion chamber. When it starts to fail, it can lead to incomplete combustion. 

This incomplete combustion leads to an increase in unburned fuel expelled through the exhaust system, resulting in higher emissions. Increased emissions not only contribute to air pollution but can also have a negative impact on your vehicle’s performance and fuel efficiency. 

When there is excessive unburned fuel in the exhaust gases, it can clog up catalytic converters and oxygen sensors, leading to reduced overall engine efficiency. 

Rough Idling and Vibrations

Have you ever started your car only to feel a noticeable vibration throughout the vehicle? Or perhaps you’ve experienced an unusually rough idle, where the engine seems to be struggling or not running smoothly. These are both common symptoms of a weak ignition coil, and they can be more than just annoying – they can indicate underlying issues that need to be addressed.

Rough idling occurs when the engine is not running as smoothly as it should be at idle speed. This can manifest as a shaking sensation or an intermittent sputtering sound from under the hood. 

While many factors can contribute to rough idling, such as dirty fuel injectors or a faulty spark plug, a weak ignition coil is often the culprit. When the coil fails to deliver enough electrical charge to the spark plugs, it can cause incomplete combustion and rough idling.

On the other hand, vibrations are typically felt throughout the entire vehicle when there is an imbalance in engine performance. Weak ignition coils can lead to misfires, which means that one or more cylinders in the engine are not firing properly. This imbalance causes uneven power distribution, resulting in vibrations that resonate through various parts of your car.

What Does A Bad Ignition Coil Look Like?

We have explained the most common symptoms of a bad ignition coil. However, many people ask whether a bad ignition coil has an altered appearance that can easily indicate something is wrong. Hence, we separated this portion. 

Well, the main visual clue to identify a bad ignition coil is physical damage. Inspect the coil for cracks, rusting, or corrosion, as this can interfere with its ability to generate the necessary electrical current. 

Furthermore, if you find oil or carbon deposits around the coil area, it could indicate leaks compromising its functionality. Remember that not all damaged coils will exhibit visible signs; therefore, it’s essential to pay attention to other warning signs we have discussed above. 

How to Test A Bad Ignition Coil

Testing a weak or bad ignition coil is crucial to ensure optimal performance of your vehicle’s ignition system. Here are some steps to help you with this process:

  • First, park the vehicle in a safe and open area away from any flammable materials and turn off the engine.
  • Next, locate the ignition coil, usually mounted near the engine block or on top of the spark plugs. Carefully disconnect the electrical connectors attached to the ignition coil by sliding them out or using a small screwdriver if necessary.
  • Take a multimeter and set it to measure resistance. Connect one probe to the coil connector’s positive terminal and the other probe to its negative terminal.
  • Check your vehicle’s specifications for normal resistance values. Typically, primary resistance should be low, ranging from 0.5 to 2 ohms, while secondary resistance should be higher, ranging from 6,000 to 30,000 ohms.
  • If either primary or secondary resistance is outside these ranges, it indicates a faulty ignition coil that requires replacement. Additionally, visually inspect the coil for any signs of physical damage, such as cracks or corrosion, that could affect its performance.
  • Replace the ignition coil if necessary based on your testing and inspection results. Reconnect all electrical connectors to their respective terminals before starting your vehicle for further testing.
  • Finally, test your vehicle again after replacement to ensure proper operation and improved ignition system performance.

Remember, if in doubt about your ability to perform this diagnostic procedure yourself, it is always recommended to consult a professional mechanic who can assist you in accurately testing and resolving any issues with your ignition coil.

How do you start a car with a bad ignition coil?

Starting a car with a faulty ignition coil can be a frustrating experience. However, you can take a few steps to get your vehicle up and running until you can replace the faulty part.

If it is confirmed that the ignition coil is at fault from the test procedure mentioned earlier, one possible workaround is using another engine-functioning cylinder as an alternative spark source. In this case, you will need to disconnect the spark plug wire from the malfunctioning ignition coil and attach it to the healthy cylinder’s spark plug instead.

Another temporary solution is employing hot wiring, which bypasses the ignition switch altogether. This method determines which wires connect directly to your car’s starter motor and battery. Connecting these wires directly using appropriate tools (like pliers) allows you to start your car without relying on the damaged ignition system.

While these procedures might help restart your car temporarily, they should not be regarded as long-term solutions. A bad ignition coil should be addressed promptly by seeking professional assistance to avoid potential damage to other engine components or compromising overall vehicle performance.


How fast do ignition coils go bad?

If the fuel-to-oxygen ratio in your vehicle is either too rich or too lean, it may result in premature failure of the ignition coils. Furthermore, the ignition coils can be damaged by engine heat and vibrations. However, in most cases, ignition coil replacement is not necessary until the vehicle has traveled 80,000 to 100,000 miles.

Can I drive my vehicle with a weak ignition coil?

While it is possible to drive with a weak ignition coil for a short period of time, it is not recommended as it can lead to more severe issues and potential breakdowns. It’s best to have the issue diagnosed and repaired by a professional as soon as possible.

Are there any preventative measures I can take to avoid weak ignition coils?

Routine maintenance, such as regular tune-ups, replacing spark plugs at recommended intervals, and keeping electrical connections clean and secure, can help prolong the life of your ignition coils.

How much does it cost to replace an ignition coil?

The cost of replacing an ignition coil can vary depending on the make and model of your vehicle and where you get the repair done. On average, you can expect to pay between $150 and $300 per coil.

Final Words

It is crucial to be aware of the signs of a weak ignition coil. From rough idling and misfires to decreased fuel efficiency and difficulty starting the vehicle, these symptoms can indicate a failing ignition coil. Ignoring these warning signs can lead to more serious issues, such as engine damage or complete breakdown. 

If you suspect that your ignition coil is weak, it is best to have it diagnosed and replaced by a professional mechanic. Don’t wait until it’s too late; take action now to ensure the proper functioning of your vehicle’s ignition system.

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