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How to Detect Faulty Coil Pack Symptoms

The coil pack has a major role in starting the car and keep the engine running without any trouble. The spark plug in the engine requires a high voltage for creating a spark and starting the combustion process. The coil pack does the job of producing that required high voltage. The engine won’t start, and your car won’t function smoothly if there’s any problem with this component. So, you need to be aware of faulty coil pack symptoms because any problem with it will lead to engine performance issues.

Faulty Coil Pack Symptoms

Your car won’t perform properly if there’s any problem with the coil pack. The usual signs of a faulty coil pack are:

  • The engine is misfiring
  • The car engine making louder sounds than usual
  • Engine is idling roughly
  • Flames coming out of the carburetor
  • Backfiring
  • Blinking engine lights
  • A drop in RPMs during acceleration
  • Exhaust puffing smell of gasoline
  • Engine light coming on
  • The car won’t start

faulty coil pack symptoms

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How to Diagnose a Faulty Coil Pack

The ignition coils are reliable but they can fail for various reasons such as vibration and extreme heat. However, voltage overload caused by plug wires or bad spark plugs is the most common reason for their failure.

If you spot any of the faulty coil pack symptoms, you should diagnose them to see if they have any problem. A few methods of diagnosing faulty coils have been discussed below:

Use an Ohmmeter

You have to measure the coil’s primary and secondary resistance to find out if it’s in a fully functioning condition, and you have to use an ohmmeter to do that.

Connect the ohmmeter to the high voltage output terminal and the positive (+) terminal to measure the secondary resistance. Reading between 6,000 and 8,000 ohms is normal if the coil is new while some coils may read more than 15,000 ohms.

Measure the secondary resistance by connecting the ohmmeter to the high voltage output terminal and the positive (+) terminal. A reading between 6,000 and 8,000 ohms is normal if the coil is new while some coils may read more than 15,000 ohms.

faulty coil pack symptoms

Other two ways of testing the resistance are to use either a spark tester that is inexpensive and available at most auto part stores or an ignition coil bench tester that is available in auto repair shops.

No matter which method you apply, never try to pull off the high voltage output wire or a plug wire to test for a spark. An open wire is risky as it can give a severe shock. Besides, sudden unplugging of wire can damage the coil by increasing the voltage demand. So, when you detect faulty coil pack symptoms, follow a proper method to test the coil’s resistance.

Check out other useful car maintenance tips provided by Car From Japan experts here!

  1. Derek says

    Rather than test primary and secondary resistances you tested secondary twice. Great otherwise

    1. Trang Tran says

      Thank u for your comment

  2. Amos nyakeya says

    I wish to know the problem with my car. When driving at 70km/h, the wheels start vibrating, what is the cause?
    Thank you

    1. tom scally says

      Balance the tires and check for any tire blemish / damage

  3. Mathews says

    My car when I start the engine, it’s start and stop then when I start again it’s start but the engine is vibrate.And when I put first gear I must use accelerate harder to able to move. And the rev counter it’s goes up and down when I stop at the stop sign

    1. tom scally says

      Sounds like a vacuum leak

    2. tom scally says

      Possible vacuum hose needs replacement or reattached

  4. Michael Kay says

    Good tips

  5. Shawn says

    Why will it fire on 3 and not the other 3 on coil pack

  6. KEV WATSON says

    I have a problem with my car, as uim driving it suddenly shuts down and stops, then it wont even turn over for a few attaempts and then restarts again after 5 minutes, could this be coil pack?

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