In this post, we discuss what causes ignition coils to keep going bad?
We look at symptoms of bad coils and how to test them and what you can do to fix them
An ignition coil is probably the most essential part of a vehicle.
It transfers the power from the battery to the spark plugs, allowing the vehicle to move.
However, despite being an important part of your vehicle, an ignition coil can quickly fail to work.
Many people complain that their ignition coil repeatedly goes bad.
Often, this coil can wear out even if you’ve recently bought it.
It’s no surprise that such issues can worry car owners.
Hence, we’re writing this article to tell you all there is to know about bad ignition coils and their symptoms.
We’ll also answer some important questions about ignition coils that can help everyone manage a bad coil problem better.
So, let’s start!
Table of Contents
What Causes Ignition Coils To Keep Going Bad?
Ignition coils can go bad due to problems with the spark plug and plug wires, an abnormal spark plug gap, extra moisture around the coil, overheating, and excessive vibrations.
In most cases, people can easily spot a problem with the ignition coil in their vehicle without having any technical knowledge.
This is because they often know some of the root causes and significant symptoms behind a bad coil.
Such knowledge helps them quickly identify coil-related issues with their vehicle without external help.
Causes Of Ignition Coil Failure
If you own a vehicle, you must know the basics causes and symptoms of a bad coil.
Let’s first start with the reasons behind a failed ignition coil, which are as follows:
1. Problems With Spark Plug And Plug Wires
Any damage to the vehicle’s spark plug and plug wires, which impacts resistance, results in a coil having a more-than-the-normal output voltage.
As a result, the coil’s internal insulation gets damaged as its voltage crosses the accepted limit of 35,000 volts.
Damage to the coil’s insulation results in a short coil.
Such a coil then gives reduced output and causes several problems to the engine.
2. Abnormal Spark Plug Gap
The electrodes in a spark plug start moving apart as the plug ages.
This increased plug gap forces the coil to generate more voltage than its capability.
Such an excessive demand from the coil leads to the coil overheating, causing permanent damage.
3. Extra Moisture Around The Coil
Oil leakages and water from the vehicle’s conditioning system can often reach the engine and coils.
This causes rust to form around the coils, and they lose their working power.
Try keeping an eye on the two moisture sources we mentioned to avoid coil damages.
4. Overheating
Weather conditions and the parking lot’s temperature can lead to overheating in the vehicle’s engine and its surroundings.
This often affects the winding and insulation of the ignition coil, affecting its working capability and performance.
5. Excessive Vibrations
A weary engine vibrates more than a well-maintained one.
These excessive vibrations damage the coil’s insulation and windings.
The vibrations can also loosen the coil’s connection with the plug, ultimately causing coil failure.
Symptoms Of Ignition Coil Failure
Now that you’re aware of what to avoid for an optimally working coil, it’s best to look at symptoms that hint at a coil’s failure.
Some of the most common ones are as follows:
1. Backfires
If your vehicle has been backfiring a lot lately, it’s about time you might need to take it to a service station for a coil replacement.
Backfiring often indicates the initial stages of ignition coil damage.
Therefore, the coil damage can be easily stopped at this point.
Backfiring occurs when unused fuel leaves the engine through exhaust pipes.
You’re likely to feel a strong jerk or two, especially when applying the brake.
Not solving backfiring issues quickly can lead to serious engine issues later, most of which require you to spend a lot on repairs.
2. Stalling
Stalling refers to your vehicle shutting off automatically when you press the brake.
Mostly, stalling is accompanied by a jerk that is powerful enough to move the vehicle a few inches forward.
Stalling occurs as a result of irregular transmission to the plugs, which is a typical symptom of coil damage.
Unlike backfires, stalling often happens in the later stages of coil damage.
Mostly, your vehicle’s consistent stalling means you’re already too late to stop the damage and must replace the coils as soon as you can.
3. Issues With Check Engine Light
Another symptom to look out for is damage to or faulty functioning of the check engine light.
Damaged coils cause misfires, and this leads a vehicle’s system to trip.
As a result, the engine check lights turn off automatically.
Sometimes, instead of turning off the check engine light, a faulty coil turns it on.
However, in this case, the problem with the coil is usually accompanied by several others.
This requires you to take your vehicle for a thorough checkup as soon as you can.
4. Poor Fuel Economy
The damage to ignition coils will most likely affect the mileage of your vehicle.
Hence, if your vehicle covers fewer miles per hour than it should with a tank full, you need to check the coils.
Mainly, poor fuel economy indicates partial damage to the coils.
However, this is not to be taken lightly, and you must arrange to get the coils without any delay.
How Can You Tell If An Ignition Coil Is Bad?
You can tell if an ignition coil is bad if you have a hard-starting engine, need more repairs than usual, or are having a rough driving experience.
Ignition coils aren’t made to last forever.
Even the most high-quality ones fail sooner or later regardless of consistent maintenance and repairs.
However, a failing coil doesn’t have to be a messy affair for every vehicle owner.
Instead, paying a little attention can make you aware of coil failure beforehand so you can easily arrange for a replacement in time.
You can easily tell if your vehicle’s ignition coil is bad by noticing the vehicle’s performance in detail.
Apart from the bad coil symptoms listed above, keep an eye on the following to quickly spot a bad ignition coil:
1. A Hard-Starting Engine
While there are many reasons behind facing difficulty starting your engine, the most common is a bad coil.
Problems with starting an engine are most common in cars that use a single coil.
In such cars, the coil’s malfunctioning causes the engine to crank without any spark inside.
This interrupts the process of the engine’s starting.
2. More Repairs Needed Than Usual
Sometimes, a poor ignition coil disrupts the functioning of several other engine components in your vehicle.
If not replaced, the failing coil quickly ruins the engine’s components, disrupting their normal working.
This leads the vehicle to demand more repairs than usual.
If you have to take your otherwise perfect vehicle to a service center every week, you better check the coils.
3. Rough Drives
Loss of power is one of the most common things to happen to a vehicle upon coil damage.
You should expect your vehicle to show signs of less power and diminished working ability when its coil requires a replacement or repair.
Look out for signs like your vehicle stopping roughly when you press the breaks and an inconsistent output even when you’re driving at a consistent speed.
These often indicate that your vehicle’s coil is going bad.
Rough and weak power output often happens in case of severe coil damage.
Hence, in cases like these, you must not take these symptoms lightly.
It’s best to consult an expert as soon as you can.
Can You Drive With A Bad Ignition Coil?
Yes, you can drive with a faulty or bad ignition coil.
Chances are, you won’t face any major issue when driving with a recently damaged ignition coil.
Sometimes you can drive as far as 100 miles even when your vehicle’s ignition coil is damaged.
Despite all of this, we still suggest you don’t drive with a faulty coil unless you have no other option.
Driving with a bad ignition coil doesn’t cause any severe harm to the car.
However, it affects the engine’s working during the drive, making your journey annoying.
Additionally, such a drive sometimes damages minor engine components.
This is of no good since it adds to your car’s repair costs and reduces its overall power.
How Do You Test An Ignition Coil?
Before you decide to replace an ignition coil, it’s best to confirm its failure.
You can get this confirmation in several ways, from the basic coil analysis to a coil test using expert tools.
Below are some of the easiest methods that you can use to test an ignition coil:
1. Coil Swapping Method
Swapping the suspicious coil with a functioning one is the easiest way to test a coil’s status.
You can use this method in case of misfires on specific cylinders.
Let’s assume that cylinder 2 in your vehicle had a misfire.
All you have to do is to remove the coil from a different cylinder and swap it with the coil from the misfired cylinder.
Now, connect the vehicle to a code reader, start it, and let the engine run for 4-5 minutes.
If your coil is faulty, you’ll get an engine code for cylinder 6 as misfired.
However, if the engine code still refers to cylinder 2 as a misfire, it’s not the coil that’s faulty but something else.
Here’s a video explaining the process:
If your coil isn’t, in fact, the problem, we suggest checking the cylinders for other issues like those in the coil connector, lead, or spark plugs.
2. General Inspection
You can also easily test an ignition coil for failure, even without any experience or technical knowledge whatsoever.
A generic yet careful inspection of a coil is probably the simplest method that anyone can use to test a coil’s status.
Interestingly, this general inspection can help you easily differentiate between a working coil and a bad one.
To carry out this coil test, you must park your vehicle somewhere under a light source.
After this, simply locate the suspicious coil and observe it with your naked eye.
Try looking for signs like burns, cracks, melting, scratches, or leakage in the coils.
If the coil has even one of these signs, it’s best to take it to a professional for repair or replacement as soon as you can.
3. Testing The Coil’s Ohm’s Resistance With Multi-Meter
Inspecting the damaged coil with a multimeter is, by far, the most accurate method of coil testing.
A multimeter helps you accurately measure the resistance in a coil’s windings.
The results of this method are often precise and valuable in determining a coil’s health.
Before moving forward with instructions on this method, it’s better to understand the basic structure of coil windings.
An ignition coil has a twisted structure with two separate coils winded around one another.
One of these coils is the primary winding, while the other is the secondary one.
Both these windings have specific resistance ranges that the coils must maintain to keep working.
Interestingly, each vehicle’s coils have different resistance in each winding.
You’ll need to check your vehicle’s manual to find out the exact resistance range that the windings in your car should have.
In case you don’t have a manual, try looking the resistance range up on the internet.
You can also contact your car dealers to find out.
Now that you know how much resistance each of the windings in your vehicle’s coil should have, it’s time you grab a multimeter.
Connect this multimeter to the coil’s terminals.
Again, if you can’t figure out where on the coil you should connect the multimeter, you can use the vehicle’s manual for guidance.
The multimeter will show you a resistance reading a few seconds after you it on the windings.
Compare these resistance readings with those specified on your vehicle’s manual.
Here’s a video showing the whole process:
If the readings are closely similar, you don’t need to do anything.
However, your vehicle will need a coil replacement if the multimeter readings fall outside the prescribed range.
In case of coil failure, the multimeter will either show you a very high reading or a zero.
A high reading indicates that the coil is open.
Alternatively, the zero on a multimeter refers to a shorted coil.
Both these cases suggest that the coil will fail any day.
Hence, you need to take it for replacement.
How Do You Stop Ignition Coils From Failing?
Unfortunately, there’s no specific way to prevent ignition coils from failing.
By now, you should know that ignition coils can fail due to several reasons.
Since there are various reasons for a bad ignition coil, stopping a cognition oil from failing is quite complicated.
Usually, the only thing you can do is ensure regular and high-quality maintenance for your vehicle.
You must take your vehicle to a repair or service station at least once a month, even if it’s in perfect condition.
Below are some maintenance-related tips for your vehicle that can help you best prevent repetitive ignition coil failure.
Following these tips can also protect your vehicle against failure of other engine components, further increasing your vehicle’s life and efficiency.
- Never trust an unknown or uncertified repair or service center. It’s best to only take your vehicle to someone who has expertise in treating the specific vehicle brand and model you own.
- Never drive back to your home from a repair station without having the coils inspected. Vehicle owners who avoid paying a little extra for coil and engine testing mostly regret later.
- Focus on what your vehicle tries to tell you. Never ignore any symptom of bad ignition coils. Instead, immediately take the car for repair even if it shows the slightest signs of coil failure.
Final Thoughts
I hope this post discussing the causes ignition coils to keep going bad has been of use to you.
We looked at the symptoms of bad ignition coils, how to test them, and what to do when you notice your ignition coils are bad.
If you ever ensure, make sure you consult your local mechanic.
