Bad Coil Pack Symptoms

What Is Bad Coil Pack Symptoms: Complete Guide

Bad coil pack symptoms can cause many problems for your vehicle and should not be ignored. If you experience any of the signs mentioned in this article, it’s vital to take action and have your car inspected by a professional mechanic as soon as possible.

Don’t let a faulty coil pack leave you stranded on the side of the road or facing expensive repairs down the line be proactive and stay on top of maintenance to keep your vehicle running smoothly and reliably for years to come.

How an Ignition Coil Works

An ignition coil is a vital component of an internal combustion engine. It transforms the low voltage from the battery into high voltage, igniting the fuel in the engine’s cylinders. This process requires three essential components: primary, secondary, and core.

The primary winding is made up of wires wrapped around a metal core. When electricity flows through these wires, it creates a magnetic field around the core.

The secondary winding sits on top of the primary winding and is wrapped around the same core. When current flows through the primary wire, it induces a voltage in this secondary wire.

This high voltage produced by the induction in secondary wiring transfers to spark plugs that ignite the fuel inside the engine cylinders. An automobile couldn’t start or run properly without an ignition coil, as no spark would ignite its fuel-air mixture.

A core is typically made from iron or magnetic steel laminations to create a path for the magnetic field generated by the primary winding to flow through. The core functions as a transformer that amplifies the voltage delivered from the battery to produce a spark strong enough to ignite fuel vapours.

The core design has evolved, with many manufacturers opting for more efficient and durable materials such as powdered iron cores, which offer lower losses due to eddy currents and hysteresis losses than traditional iron cores.

Spark plug

Bad Coil Pack Symptoms

The spark plug plays a significant role in creating and igniting these electrical sparks. The spark plug consists of two electrodes separated by a gap, and when electricity passes through them, it creates a spark that ignites the fuel-air mixture inside the combustion chamber. This explosion pushes down on the piston, turning the crankshaft and powering up your vehicle.

Ignition distributor

It is the interface between the high-voltage coil and the spark plugs, allowing for accurate timing and distribution of electrical pulses to each cylinder. The distributor has a rotor and cap that rotate to distribute power from the coil to each spark plug wire.

When the key is turned, power from the battery flows through the ignition switch and into the primary winding of the ignition coil.

This creates a magnetic field that stores energy until it is released by breaking or opening one of two sets of contacts in an electronic ignition system or by having current flow through a set of breaker points in older systems.

Symptoms of a Bad Ignition Coil – Symptoms of bad Coil Pack

A bad ignition coil can cause various issues with your vehicle, and it’s essential to recognize these symptoms as soon as possible.

Backfiring: When an ignition coil fails, it sends an irregular spark to one or more cylinders in your engine. This can result in unburned fuel entering the exhaust system and igniting, causing loud pops or backfiring when accelerating or decelerating suddenly.

Bad ignition coil: You might experience rough idling or stalling when you come to a stop, or your car may struggle to accelerate smoothly from a standstill or at low speeds. The engine may also misfire, causing noticeable vibration and noise while driving.

Engine stalls: When the spark plug doesn’t receive enough voltage from the ignition coil to ignite the fuel and air mixture in the combustion chamber. The engine may start but stall shortly after or while driving down the road. This can be particularly dangerous if travelling at high speeds or navigating through busy intersections.

What is Backfiring?

Backfiring is a term used in the automotive world to describe an engine problem when the fuel mixture ignites outside the combustion chamber.

This results in a loud popping or banging sound from the exhaust system. Backfiring can occur for various reasons, including incorrect air-to-fuel ratios, timing issues, and problems with the ignition system.

One common cause of backfiring is an overly lean fuel mixture. Insufficient fuel enters the combustion chamber to ignite properly, causing it to burn outside the engine.

Another cause could be improper timing, where spark plugs are firing too early or too late, causing unburnt fuel to exit the exhaust pipe and ignite instead. Damaged spark plugs or wires could cause intermittent sparking leading to backfires.

What Does It Mean When Your Engine Is Hard to Start?

When you turn the key in your car’s ignition, and it takes longer than usual to start, it could indicate a problem with your engine. Several factors, including a weak battery or starter motor, a clogged fuel filter, or faulty spark plugs, can cause a hard start. It is crucial to promptly determine the root cause of the issue to avoid further damage to your vehicle.

A weak battery is one of the most common reasons for a hard start. If your battery is old or has been drained due to leaving lights on overnight or other reasons, it may need more power to turn over the engine.

If your starter motor fails, it may struggle to crank the engine and cause difficulty starting. Dirty spark plugs can prevent proper combustion in the engine and make starting more difficult.

Signs of a Poor Fuel Economy

If you notice that your car is using more gas than usual or you have to fill up the tank more frequently, this could be a sign of low fuel efficiency. One of the most frustrating signs of poor fuel economy is a need for acceleration starting from a stop.

This also could indicate that something is wrong with your engine or transmission. Fuel injectors may become clogged over time and require cleaning or replacement, resulting in decreased power output.

Vehicle Stalling: Bad Coil Pack Symptoms

By failing to keep up with oil changes, tune-ups, and other routine maintenance tasks, drivers are putting their cars at risk for problems down the road. Regular maintenance keeps the engine running smoothly and helps prevent stalling by ensuring all components work as they should.

Check Engine Soon Light

The check engine soon light can be a source of anxiety for many drivers. It indicates that something in your vehicle isn’t working as it should, often leaving you guessing the issue.

Bad Coil Pack Symptoms

The check engine soon light can be triggered by various issues, including these:

  • Insufficient pressure of fuel in the fuel rail.
  • An ignition coil that is not functioning properly
  • The vehicle’s electronics malfunctioned.
  • An O2 sensor that is not functioning correctly.

Average Ignition Coil Replacement Cost

When the ignition coil fails, you will notice that your car won’t start or will misfire, so you need to replace your ignition coil. The cost of replacing an ignition coil varies depending on factors such as the make and model of your car, location, and labour costs involved.

On average, you can expect to pay between $150 and $350 for an ignition coil replacement job. This cost may increase significantly if you have a luxury car or one with a complex engine design.

When to Get a Vehicle Check

If you notice any unusual sounds or smells coming from your car, you must get it checked immediately. This could indicate a problem with the vehicle’s engine, brakes, or other crucial components. If you have recently purchased a used car, getting it inspected before driving it for an extended period is recommended.

Regular maintenance checks are also necessary to keep your vehicle in good condition. You should take your car for servicing every six months or after every 10,000 km driven (whichever comes first).


Bad coil pack symptoms can be frustrating and dangerous for drivers. It is essential to recognize the signs of a failing coil pack and have it replaced as soon as possible. Ignoring these symptoms can lead to more serious engine problems that could result in costly repairs.

By staying proactive and addressing any issues with your vehicle, you can ensure a safe and reliable driving experience. Take action now to keep your car running smoothly before you’re stranded on the side of the road – take action now to keep your car running smoothly.


How many years do coil packs last?

Coil packs typically last around 3-5 years. It depends on how often the pack is used and how well it is handled.

How does a coil pack get damaged?

The most common is when the coil pack becomes wet, and the insulation breaks down, letting electricity flow through the coil pack and into the battery. This can cause a short circuit, damage the battery, or even start a fire.

What do bad coils sound like?

When a coil in an electronic device fails, it can create an audible buzzing or humming noise. This is due to the electrical current flowing through the coil becoming distorted.

How to tell if a coil pack is bad?

If the coil pack is not working, it isn’t good. To test a coil pack, remove the battery and plug in an external power supply. If the pack starts up, it is likely good. If it does not start up, the pack may be harmful and should be replaced.