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Symptoms of Faulty Ignition Coils

Symptoms of Faulty Ignition Coils


The ignition coil is the source of the spark that ignites the air-fuel mixture in the engine's combustion chamber. The ignition coil receives a voltage of 12V from the car's battery and multiplies it to a higher voltage level. The multiplied voltage is then delivered to the spark plugs at the right time, which in turn ignites the air-fuel mixture in the cylinder. Knowing the signs of failure of ignition coils can save you a whole lot of time and trouble. Of course, a faulty ignition coil will have a bad influence on the engine's performance. This specific section concentrates on the symptoms exhibited by an ignition coil when all is not fine with it.


How Much Does a Ignition Coil Cost?

Engine Stalling

A weak spark is the first sign that the ignition coil may be failing. During acceleration, the air and fuel that is forced into the cylinders extinguish whatever spark there is, which causes the car to stall. So, if a car is running on a weak spark, the car will be able to turn on, but will stall out soon after acceleration. If you have already ruled out that you don’t have a faulty battery, the ignition coil may be something to look into.

Oil Leak

Most ignition coils are fitted within a housing that is filled with oil. If the coil overheats, the housing will break, causing an oil leak. An oil leak can mean that you have a flooded carburetor and the vehicle will run very poorly. Double check to see if there is clear oil leaking around the ignition coil housing, and be sure to replace the coil before it completely fails.

Car Won't Start at All

In some cases, complete failure of the ignition coils will prevent you from turning on your car at all. If there is a clicking noise when you try to turn over the car, you can rule out the ignition coil. But, if there is no noise at all, this is an indication that the ignition system has failed. A failed coil will prevent any spark, and in turn, no combustion for the car to turn on.

Degraded Performance of the Catalytic Converter

A weak spark will fail to burn the air-fuel mixture fully, which causes the incompletely burned fuel to exit along with the exhaust gases. Fuel in the exhaust can be detrimental to the catalytic converter. If the catalytic converter goes bad, it will result in increased emissions and poor engine performance.

Some of the above mentioned symptoms also indicate a failure of other ignition system components such as the spark plug or its wires and distributor cap. Do a proper check to detect the right issue and attend to it as soon as possible. If you are unsure, consult with a certified mechanic and get the problem addressed at the earliest.

A faulty ignition coil triggers the OBDII check engine codes from P0300 to P0312 and P0350 to P0362; each code implies a specific problem with the ignition coil.

Replacing the ignition coils can be done by any regular DIYer. We always recommend following the safety precautions specified in your owner's manual.

Other Related Topics

If you are interested to know about the function, working and other aspects of the ignition coil in detail, along with tips on buying a replacement coil for your vehicle, you can read through our buyer's guide. has composed a “We Make it Easy” video series which includes videos of different installation and maintenance procedures. The video depicting how to replace ignition coils can be found here.

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