How To Test The 4 Cylinder Coil Pack (Ford 1.9L, 2.0L)

Testing the Ford ignition coil packs on the 1.9L and 2.0L Ford, Mercury and Mazda equipped cars is pretty easy. This article will walk you thru' the whole diagnostic/troubleshooting process to find out what's causing your car to misfire.

This article covers the two incarnations of the Ford coil pack for four cylinder engines. One is the early type and the other is the late type design. Although they are not interchangeable (since their connectors are different), they are tested in the same way. To see examples of the two styles, go to the section: Circuit Descriptions Of The Ford Coil Pack Connector.

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Symptoms Of A Bad Ford Coil Pack

When the ignition coil pack or the spark plug wires are bad, your Ford (or Mercury, or Mazda) vehicle will display one or more of the following symptoms:

  1. The car idles rough and wants to stall (die).
  2. When you accelerate the car, it has no power.
  3. Really bad gas mileage.
  4. The vehicle will not start.
  5. The car will not run on all cylinders.
  6. Misfire codes that are lighting up the check engine light on your instrument cluster.
    • P0300, P0301, P0302, P0303, P0304.
  7. Rotten egg smell coming out of the tail-pipe.

What Tools Do I Need To Test The Ignition Coil?

To successfully use this information to diagnose and troubleshoot your Ford (Mercury or Mazda) four banger, you need a few specific tools. Don't worry, none of this stuff is expensive, here's the list:

  1. A 12 Volt test light.
  2. A LED light.
  3. An HEI spark tester
  4. Battery jump start cables.
  5. Someone to help you crank the car.

To troubleshoot and diagnose a bad coil pack on your Ford (or Mazda) car, an HEI spark tester is a must have tool. Using the wrong tool or method will have you chasing a wrong diagnostic test conclusion and effectively wasting your time and money.

Circuit Descriptions Of The Ford Coil Pack Connector

How To Test The 4 Cylinder Coil Pack (Ford 1.9L, 2.0L) How To Test The 4 Cylinder Coil Pack (Ford 1.9L, 2.0L)
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The Ford coil pack connector has three wires coming out of it. No matter what the style of coil pack or the style of connector that connects to it, the circuit descriptions are the same.

  1. Circuit labeled 1:
    • Switching signal circuit for spark plugs 1 and 4.
  2. Circuit labeled 2:
    • Power (12 Volts) circuit
  3. Circuit labeled 3:
    • Switching signal circuit for spark plugs 2 and 3.

You've probably noticed that there's no mention of the color of the wires of the three wires coming out of the connector, well the color is not important (to take advantage of the info in this article) as long as you're able to correctly identify the circuit by its number in the photos supplied.

Basic Operating Theory Of The Ford Coil Pack

How To Test The 4 Cylinder Coil Pack (Ford 1.9L, 2.0L) How To Test The 4 Cylinder Coil Pack (Ford 1.9L, 2.0L)
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The PCM (Powertrain Control Module=Fuel Injection Computer) is the one that controls the whole show in this type of ignition system since the 'Ignition Control Module' function is handled by the PCM itself. So, in a nutshell, here's what happens when you turn the key to crank and start the car:

  1. The engine starts to crank, inducing the crankshaft position (CKP) sensor to start producing its CKP signal.
  2. The CKP signal, upon being received by the PCM along with other necessary sensor information, starts to do its little song and dance and sends back two different Switching signals (thru' separate circuits) to the ignition coil pack.
    • The coil pack is made up of two separate ignition coils. Each ignition coil within the coil pack has two towers that feed spark to two cylinders at the same time.
    • The term Switching signal describes the PCM's action of switching the Primary Current (12 Volts), flowing thru' each ignition coil within the coil pack, ON and OFF by interrupting their Ground path. It's this signal that makes the ignition coils fire spark.
    • Each ignition coil (that make up the coil pack) get their own switching signal from the PCM.
  3. As each individual ignition coil, within the ignition coil pack, get their Switching signal, they then fire spark to two different cylinders at the exact same time (in what's known as the Waste Spark method).
    • One ignition coil within the coil pack fires spark to cylinders 1 and 4.
    • The other ignition coil that makes up the other part of the coil pack fires cylinders 2 and 3.

You don't need to memorize any of this since this article will take you step by step thru' the whole testing and troubleshooting process so that you can replace the right component, saving time and money in the process.

Precautions, Do's And Don'ts

Most of the testing that you'll be doing is with the engine cranking, so take all necessary safety precautions to keep your fingers, hands and entire self safe. Here are a few other tips and suggestions:

  1. Do not use a regular spark plug instead of a spark tester to test for spark.
  2. Do not remove the spark plug wire from the spark plug or the ignition coil while the engine is cranking to test for spark.
  3. Start your diagnostic from TEST 1, do not skip around from test to test unless instructed to do so by the TEST you are currently on.
  4. Do not use a test light where an LED light is called for.
  5. Once again, use the recommended/indicated tools for all of your tests.