Signs Of A Bad Or Failing Ignition Coil

A bad ignition coil can give you trouble while starting your car. An ignition coil transforms the energy in the battery to a higher voltage to ignite the fuel in the cylinder. If your vehicle loses power as you drive on the highway, here is what could happen and what could be causing it. However, first, let’s get through how it works in order to understand how such signs are produced.

How Does The Ignition Coil Work?

An ignition coil is a mini electrical transformer fitted in your car, converting the normal 12-volt current found in the car battery to ignite the fuel and start the engine. Ignition coil has its own spark plug connected to it by a wire or sitting on its top. It needs 15,000 to 20,000 volts of electricity for a spark plug to generate a spark to ignite the fuel. The coils are usually protected in oil-filled housing, which acts as a refrigerant. It has two windings wrapped around the iron core; primary and secondary. This arrangement makes the ignition coil a compact step-up transformer. The number of turns of the secondary winding is always more than the primary winding resulting in a higher conversion of current.

If the ignition coil is unable to transform the energy strongly, then the fuel consumption is weaker, which results in the engine misfiring. The older car batteries can easily breakdown with time; it should at least read 12.65 volts in a fully charged state, or otherwise, this is a sign of a bad ignition coil.

7 Bad Ignition Coil Symptoms

Experiencing driving issues related to combustion process hints possibly towards a bad ignition coil. We have compiled a list of common symptoms to understand when your ignition coil has gone bad. Note that each symptom would differ depending on the severity of the breakdown.

1. Backfiring

Backfiring is one of the most common signs of a bad ignition coil. Backfiring refers to the condition when the unused fuel left in internal combustion cylinders ends up flowing out of the exhaust pipe. The ignition coil malfunctions and doesn’t spend enough signals to the spark plugs leaving unused fuel behind. This makes the fuel-to-air mixture too rich, and the unused fuel starts coming out of the exhaust. Ignoring this sign is a bad idea because it can result in costly repairs lately.

The usual sign of backfiring is the black smoke coming out of the exhaust pipe. The smoke may also give off gasoline smell indicating the ignition coil failure. The smell comes off the unused fuel exploding before coming out, resulting in greater damage to the engine later on.

2. Engine Misfiring

If you turn on the car engine and hear a coughing or spluttering sound, again and again, it indicates that the engine is misfiring or doesn’t fire at all. Engine misfiring usually results from a bad ignition coil. Your car will start jerking and spitting at high speed. It will vibrate upon idling at a signal. Misfiring usually happens when the engine is under load. Your car will even hesitate while accelerating, and you would feel like you are missing on the power to drive. The dense emissions can ruin other important parts like catalytic convertor or air-fuel mixture sensors. This can result from a fuel delivery system or spark plug problems too. You can still drive your car, but it’s better to take it to the mechanic as soon as possible.

3. Stalling Vehicle

A failing ignition coil will cause vehicle stalling. Your car will come to a stop completely while idling, leaving you confused as you try to restart it repeatedly. The faulty ignition coil sends the inadequate spark to the spark plug resulting in installing a vehicle. If the problem is ignored and aggravated, your car will stop suddenly while starting, accelerating, stopping, or simply driving. Transmission problems, idle air control actuator or a clogged EGR valve could also result in such conditions. You need to get it checked at an auto shop near you.

4. The Engine Is Hard To Start

A hard starting engine is a sign of a car with one ignition coil. If the vehicle totally depends on a single ignition coil, its malfunction will cause you a lot of trouble even though problems can result in more than one coil installed. This issue has no relation with configuration. If the spark plug doesn’t receive much power, you will not be able to start your car. The cranking sound of the cylinders indicates the weak sparks but a working ignition coil. The cranking sound of the cylinders indicates the weak sparks but a working ignition coil.

5. Leaking Oil

A malfunctioning ignition coil can overheat in no time. This results in the housing wiring to break leaking the oil into the surroundings. The leaking oil could also result from a gap in spark plugs due to corrosion. The ignition coil works at a higher voltage, and as it is already working harder, it will overheat.   

6. Check The Engine Light

If you find the engine’s light on at your dashboard, unexpectedly, this means that there is something up with the ignition coil. You can drive your car to the mechanic for the OBD-II check. The engine will show up with the DTC code P0351 upon the check, which predicts ignition coil, primary, or secondary circuit malfunction. You can grab an OBD scanner and check it on your own to troubleshoot a coil issue.

7. Poor Fuel Economy

Another evident symptom of a bad ignition coil is poor fuel economy. You can easily determine your car’s average fuel consumption if you have been driving it for a while. If these days your car is offering less mileage with the same amount of fuel, then you need to check on the ignition coil. The system compensates the lower power generated by the spark plug by utilizing more fuel. This also happens due to the malfunctioning of oxygen sensors. A bad fuel injector can also leak the fuel.

How To Prevent A Bad Or Failing Ignition Coil

The best way to keep your car in good shape is to pay close attention to every part of the ignition system. Keeping an eye on the spark plug can help you to save money in the long run, saving you from costly repairs. Check the plugs for erosion and if they aren’t worn out. Check for the housing for leakage. Check for the ignition system wires not to be toasted, and in case you find any of the above-listed things in bad shape, then go for maintenance as recommended by your vehicle manufacturer.

Testing A Failing Ignition Coil

Based on if the coil is CNP (Coil-Near-Plug) or COP (Coil-On-Plug), here is how you can test an ignition coil.

COP Coil Type:

  • Turn on the engine.
  • Keep it running at a steady speed while the car is idle.
  • Open the first ignition coil bolt. Pull it up to check how the engine works. If the engine starts running too rough idling, this is a sign that the first ignition coil is fine.
  • Repeat the process with the remaining coils one at a time until you find the faulty ignition coil.
  • Once you find it, pull it out you will notice that the engine condition wouldn’t change.

CNP Coil Type:

  • Stop the engine of your car and open the hood. Pull out the spark plug wires. The CNP coil type run from the distributor cap to the spark plug. Wear rubber gloves and use insulated tools while operating electrical components to keep yourself safe from a nice jolt.
  • Attack the new spark plug to its wire to test coil sparks. Hold the spark plug with insulated pliers by placing it onto the metal part of the engine, so you are not in contact with the threaded portion of the spark plug.
  • With a fuse removal tool or needle-nose pliers, remove the fuse from the fuel pump and crank the engine. You will need some help to turn on the engine at the same time.
  • Look for the blue sparks formed along the spark plug gap after the engine is cranked. Blue sparks mean that the ignition coil is totally fine.
  • If you witness am orange spark or no sparks at all, so this is the bad ignition coil you have been searching for.
  • After finishing the test, remove the spark plug while placing it back into its hole. Connect the wires back to the spark plug and put the fuel pump fuse back.

Cost Of Repairs And Ignition Coil Replacement

The cost of repair and replacement depends on the model of your car. You can find a coil as low as $75 or as costly as $300. If you have hired a professional to get it done so don’t forget to add $50 – $100 to the total cost for labor. Getting average ignition coil replacement done at an automotive repair shop will cast you at least $150 to $200. Going for a dealership, you might need to pay extra.

 To sum it up, if you notice any of the above-listed signs such as backfiring engine misfire vehicle stalling engine light turning on poor fuel consumption and oil leaking, you need to get it checked for a bad ignition coil. Otherwise, keep your car maintained to avoid most of the problems with the ignition system to enjoy a safe and fun ride.