Can A Bad Coil Cause Knocking? (Explained)

When you look through the common signs and symptoms of a bad coil, you won’t see knocking on the list. The same also applies when you read through the causes of engine knocking.

However, even though a bad coil isn’t listed as one of the causes of engine knocking, that doesn’t mean it can’t be a culprit.

If you are currently experiencing some engine knocking and you think that bad coils are the cause, this article will shed more light on the matter and help you find the best solution.

Car mechanic replacing ignition coil on gasoline engine

Will an Engine Knock Because of a Bad Coil?

Engine knocking can be caused by plenty of things. However, a bad coil isn’t often one of them. A car with a bad coil will cause the engine to misfire. The sound produced may imitate that of a cough or sputter.

You will not hear pinging or knocking. Engine noises can be different, and when a certain component in the vehicle malfunctions, you will notice a change in the engine noise.

This is one of the ways car owners use to diagnose faulty engine components. It’s important to know that knocking isn’t a sign of a bad coil.

What Can Cause an Engine Knock in Your Car?

Even for those who have never experienced a knocking engine, the phrase is widely used to drive terror and fear among car owners.

There is a valid reason why you should be afraid of engine knocking. It can lead to costly repairs and replacements if the underlying culprit is not addressed.

An engine knock is an indication that there is something wrong with your car. The pinging or knocking sounds are different from what your engine sounds like; therefore, it’s easy to hear them. They usually become louder when you speed up.

If you hear a knocking sound on your engine, you should have it diagnosed by an expert mechanic to determine the cause and fix it.

As you plan on doing that, you should also familiarize yourself with some of the common causes of engine knocking.

1. Using the Wrong Type of Gas

After buying a car, you need to familiarize yourself with the type of gas that the car consumes. If possible, you should write it down somewhere so don’t forget and fill in the wrong gas.

One of the leading causes of engine knocking is using gas with a low octane rating. The knocking, in this case, will be more severe as you accelerate.

If you didn’t refill the wrong type of gas, there is a high chance that the gas in your tank was the incorrect one. Fuel with a low octane rating should lead to premature combustion, which would then cause knocking.

Suppose you have made this mistake. There are two options. The fuel tank can be stripped dry and replaced with the correct fuel. Alternatively, you can add an octane booster. Your mechanic should recommend the best remedy.

2. Faulty Knock Sensor

In modern engines, knock sensors are used to prevent knocks. When you use a fuel with a low octane rating, the knock sensor signals the engine to retard the ignition and avoid damage.

The knock sensor may perform perfectly for the better part of your car’s life. However, as time goes by, it also experiences wear and tear.

Therefore, it can begin sending wrong signals, thus leading to an engine knock. The best fix for a faulty sensor is an immediate replacement.

3. Bad Timing

The computer in your car controls the timing of the engine when the spark plugs will fire. Should the timing be off, there will be several detonations on the cylinder, and that would cause knocking. Cars with adjustable ignition do not experience this problem. It’s more common in recent models.

To fix the ignition timing, you will need the assistance of an expert mechanic who will attempt to retard the timing and ensure the ignition occurs at the correct and designated period.

4. Lean Air/Fuel Mixture

This is a mixture that contains a lot of air, more than needed, and very little fuel. A lean air and fuel mixture is caused by faulty airflow sensors, fuel pumps, injectors, and oxygen sensors.

The combustion won’t be fast enough when this happens, and the engine will start to knock.

5. Worn Bearings

The bearings in an engine play a critical role in ensuring smooth piston movement. Being a mechanical component, the bearings can get worn out after some time.

They can even come out of their original position as they move up and down. This will lead to the production of a rattling sound within the crankshaft. Worn bearings are a serious problem and will require immediate intervention.

6. A Faulty Belt

When you look at an engine in action, you will see a belt that turns different pulleys. This belt can also lead to clicking and rattling of metal when it loses shape, or the tension is altered.

At times knocking doesn’t always come from the engine. This is a good example. Having this belt inspected and set at the correct tension can stop that noise.

These are the most common causes of engine knocking. As you have seen, a bad coil wasn’t listed anywhere in the above list. That’s because a faulty coil doesn’t manifest itself in the form of a knocking engine.

What are the Signs of a Bad Coil?

Having ruled out that engine knocking isn’t a sign of a bad coil. Let’s look at the actual signs and symptoms of a bad coil. If you are experiencing any of these issues, you can diagnose that a bad coil is the culprit.

But first, what is an ignition coil?

It’s a low-current high voltage transformer that transforms a 12V battery into more than 25K volts to create a spark in the engine.

This spark ignites the air and fuel mixture so that the engine can start. Without an ignition coil, the car won’t be able to start, and that only proves how useful this component is.

The best way for you to determine if an ignition coil is faulty is by having it diagnosed by an expert. Nonetheless, a couple of warning signs can help you determine if a coil is malfunctioning.

1. Illumination of the Check Engine Light

Modern cars have made life pretty easy. If your ignition coil isn’t working or it’s malfunctioning, the first warning sign will be the illumination of the check engine light.

In some cars, it will be more specific when a diagnostic tool is used, and it will indicate the problem as code P0351, which translates to issues with the ignition coil.

2. Backfiring Engine

One of the most common signs of a bad coil is an engine backfire. This happens when unused fuel gets out via the exhaust of the internal combustion cylinders.

An engine backfire is characterized by black smoke coming from the exhaust and a foul gasoline smell. A backfiring engine is harmful to both the environment and the car. Ensure that you have the coils checked right away.

3. A Stalling Engine

If your coils are malfunctioning, then the vehicle won’t be able to ignite the fuel-air mixture efficiently. This can lead to stalling of the engine.

If the engine has started stalling, you should replace the coils as soon as possible to avoid the car stopping completely.

4. Poor Gas Mileage

If you have a bad coil, the amount of money you will be spending on gas will be high. What happens is that a bad coil will push the engine to produce more power, thus increasing the amount of fuel intake.

If you have recently realized a decrease in fuel economy, inspect the condition of the coils.

5. Abnormal Engine Noises

A car with a bad coil will produce loud engine noises characterized by high vibrations. You need to differentiate between loud noises and knocking sounds.

We have already ruled out that engine knocking sounds aren’t a sign of a bad coil. Because a bad coil leads to engine misfires, you may hear a coughing or sputtering sound.

How Do I Replace a Faulty Ignition Coil?

The reason we have listed the above signs of a faulty coil is to show you that it has got nothing to do with causing engine knocking. If you are experiencing knocking sounds, you should go through our list of common causes.

Be as it may, if you have a faulty ignition coil, you must test it first. A test will give you an accurate answer on whether the coil is the source of your woes. If it is, you can proceed to replace the affected coil.

An ignition coil replacement is a fairly easy process that shouldn’t take very long, provided you have already bought the replacement coil. Start by turning off the car engine and disconnecting the battery.

This is a piece of electrical equipment, and it should be removed when the vehicle has been switched off. After doing that, what’s left is to identify the location of the coils.

They are usually at the top of the engine. You can remove them and connect the new ones. Put the coils back in position, reconnect the battery, and switch on the car.

You should notice a difference in the engine noises. The car shouldn’t be misfiring. If you can still hear the knocking, it’s time to bring in the experts.

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