Repeated Ignition Coil Failure – What Are the Common Reasons?

If ignition coils keep failing in your car and you can’t do anything with this, I will outline in this article several common reasons for this. Also, I will show you how to check the ignition coils, understand the symptoms of their failing, and even prevent them from failing too often.

In short, repeated ignition coil failures are possible as a common fault in some engines, because of bad spark plugs, wiring issues, ECU problems, contamination, or overheating. This is not the full list of common problems that kill your ignition coils, but these are the most possible ones. Also, the coils may fail because of poor mounting or bad quality of the parts.

In this article, I will tell you about the following:

• The symptoms of failing ignition coils.
• Most common factors that spoil ignition coils.
• Can you drive with a bad ignition coil?
• How to prevent your ignition coils from failing?

Symptoms and signs of bad ignition coils

Readers often ask me if a bad ignition coil can throw a check engine light. The coil itself doesn’t have any sensor that would tell the ECU that the part is malfunctioning, so there is no such code that would point at the bad coil. But the check engine light may go on when the engine misfires heavily. The ECU can count the events of misfiring and when the number reaches certain times a minute, the check engine light goes on.

Here are the symptoms of a bad ignition coil:

1. The engine is misfiring. It means that one of the cylinders doesn’t do the job because the air-fuel mixture wasn’t ignited at the right time due to coil failure.
2. The check engine light is on. The most possible codes are P0300 and all the family of P0301, P0302, P0303, etc. The last digit means the number of the cylinder that experiences problems.
3. The car loses power. If you have a 4-cylinder engine, it becomes about 25% less powerful because it basically loses one cylinder.
4. The engine works harshly. It can vibrate more than usual, stall, die unexpectedly, throw some other random codes, etc.
5. The acceleration is way worse than usual. Your acceleration may take twice more time as usual because the power is bad and the engine is unstable.
6. When idling, the engine may shut off. Also, it vibrates like crazy, the RPM goes up and down.
7. The engine may backfire. You may even see the fire going off the tailpipe. This is because the unburnt fuel goes to the exhaust system and burns there.
8. The engine sputters and coughs. When you try to accelerate and press the gas pedal, your engine may sputter. ECU limits its power and tries to balance its work.

These are the most common but not all possible symptoms of a failed ignition coil. Also, the same symptoms may be applied to the failed plug, a bad wire that connects the ignition coil to the control unit, etc. If two or three coils fail, the engine is not likely to start and work. Also, you will not be able to drive such a car because it will have as much power as a scooter.

Here’s why your ignition coils may fail so often

Now, we’ve come to the most interesting part – why do the ignition coils in your engine fail so often? They cost quite a lot and buying a couple of coils every other month is not something you want to spend your hard-earned dollars on.

Unfortunately, one of the answers is the engine type. There are engine models that just kill ignition coils because of their bad engineering. You can’t do anything with that – they just kill the coils with excessive heat or bad programming.

Find the list of common problems with your engine and look through it. Do you see the ignition coil failure as one of the bullets in that list? Then, most likely, you just need to put up with this. Buy OEM coils to let them work a little longer than aftermarket parts would last.

But here are some other factors that can kill ignition coils much faster than expected:

1. Dying spark plugs

It’s important to replace spark plugs in your engine before they fail. Again, you can google and find out spark plug replacement intervals that experienced mechanics recommend for your engine.

If the plug fails, it can send current to the coil rather than convert it to the spark and ignite the fuel. The bad spark plug will quite quickly kill the coil and may even do other bad things. You may want to check your spark plugs every time your car is on regular maintenance.

2. Bad wiring

Your coils get signals from the ECU or other control units through wires. It means that one of the wires may lose contract or just be broken. This can not only kill the ignition coil by sending wrong signals to it, but also show the symptoms of the dead coil and make you buy the new one, and install it to just see that there is no difference in how engines work now.

Wiring is harder to check, but there is one trick. Swap two coils and see if the problem moved to another cylinder. For example, if the code meaning misfire moves to another cylinder, the coil is the culprit. But if the misfiring cylinder code stays on the same cylinder, then the problem is not in the coil but in the plug or wiring.

3. Cheap and poor-quality coil

OEM ignition coils may cost a fortune, so we often hunt for cheaper options online. And there are plenty of them available in numerous stores. But the quality of those parts is not really high.

Also, you can buy a coil that is not completely compatible with your engine and it will die on the second day.

If you don’t want to pay for OEM ignition coils, you should at least choose the parts made by reputable brands and offered with at least some warranty.

4. Bad mounting

Installing the ignition coil doesn’t seem to be a hard task. Just unscrew several bolts, take the old coil off, install the new one, and screw those bolts back. But if you mess with the wires or don’t fasten the bolts as they should be fastened, chances are that the coil will be loose and eventually will fail because of short circuit or other problems.

It’s always better to let professionals do this job – it won’t cost you that much money because the process takes 10 minutes only.

5. Water damage

If you spill some water or coolant (or any other liquid) directly onto the upper part of the engine, chances are this water will get to the coils. It means that the coil will most likely fail because these electrical components can’t stand any contact with liquids. They can even kill the plug and burn the wiring if this happens.

Avoid water contact with the coil. Even if the raindrops fall onto the engine when the hood is open, there is a high risk of problems with the coils.

How often should you replace ignition coils?

Well, there isn’t a certain answer to this question. On average, an ignition coil should last at least 100,000 miles. Some will last as long as the engine. But some will only get to 20K miles and then die.

It depends on so many factors including the construction of the engine, the temperature in the engine head, and especially in the spark plug wells. Also, it depends on the manufacturer and type of the coil.

Can you drive with a bad ignition coil?

If one coil is dead or malfunctioning, you still can drive. But driving won’t give you any pleasure. One cylinder will be heavily misfiring or it may even be dead, so the engine will have about 75% of the power and it will work extremely harshly.

There are several problems with the dead ignition coil:

• the fuel is still injected into the cylinder and it will burn in the catalytic converter or go down to the oil pan and dilute the oil;
• the ECU will see the cylinder misfiring and will throw a code (check engine light will go on);
• your gas mileage will drop;
• you will most likely kill the plug;
• there is a risk that the bad coil may also fry wires and even damage the ECU.

So, I don’t recommend driving for a long time with a dead ignition coil. It will influence the health of other parts and may even lead to severe consequences if you continue driving your vehicle with this problem for too long.

How to prevent ignition coils from failing?

In the final part of this article, I want to tell you that there isn’t much you can do to help the coils live longer. They will still die and require replacement. This isn’t a tragedy, just modern engines work like that. It’s important to not miss the moment when you need to replace the old and broken coils.

Here are some factors that can prolong the life of coils:

• Change spark plugs regularly

One vehicle needs spark plug replacement once every 30,000 miles, in another engine, they can go 60K miles. Just don’t miss the point when the old plugs should be replaced to avoid problems.

• Buy high-quality coils and plugs

Bad spark plugs may start killing ignition coils from day one. Also, cheaper coils may melt and be destroyed after just several weeks of driving. So, avoid cheap and low-quality parts.

• Be careful with DIY repairs

It’s enough to over-tighten the bolts or make the loose connection between the spark and the coil to kill both quite quickly.

• React to codes, messages, and warning lights

If you see the check engine light and feel that the engine delivers low power, you should inspect the vehicle. If the scanner shows the P0300, P0301, P0302, or other similar codes, go to the dealership or to the good repair shop and ask for a good inspection.

Final thoughts

Unfortunately, in some vehicles, ignition coils just don’t live long. You may even want to have a spare coil in your glove box just in case it goes bad right in the middle of nowhere. But in other cases, coils may break down so often because of one of the reasons I’ve outlined above and you can change this.

Understanding how ignition coils work and why it’s important to maintain the entire ignition system in good condition will help you prolong the life of your ignition coils and make sure that the engine works at its top efficiency level.