How To Diagnose A Misfiring Cylinder (2.3L Ford Ranger, Mustang, B2300)

2.3L Equipped Ford. How To Test For A Misfire

Diagnosing the cause of the misfire (rough idle) on a 2.3L equipped Ford Mustang or Ranger (Mazda 2300) can seem quite daunting since you have 8 spark plugs and two coil packs to deal with.

Not only that, but quite a few things can cause a misfire condition (or misfire trouble codes).

In this tutorial, I'm gonna' present to you the basic causes of a misfire condition (rough idle) and a specific diagnostic strategy that will help you get to the bottom of the issue.

I'm also gonna' show you were you can find the specific test tutorials you'll need. Let's get started.

In Spanish You can find this tutorial in Spanish here: Cómo Probar Un Falla En Cilindro (2.3L Ford Ranger y Mustang) (at:

Symptoms Of A Misfire Condition

Whether your specific 2.3L Ford Mustang or Ranger is OBD II equipped or not, a misfiring cylinder simply means that that cylinder is not pulling all of its weight.

In other words: If the engine is misfiring, the engine is simply not firing on all cylinders. Now, since the 2.3L Ford engine is a four cylinder, having just one ‘dead’ cylinder will cause an impact on engine performance and you're gonna' definitely feel it as you're driving down the road or stopped at a traffic signal.

Here are some of the most common symptoms:

  1. The check engine light (CEL) will be on.
  2. One or more misfire codes will be stored in the PCM's memory (if OBD II equipped).
    • P0300 Random Cylinder Misfire.
    • P0301 Cylinder #1 Misfire.
    • P0302 Cylinder #2 Misfire.
    • P0303 Cylinder #3 Misfire.
    • P0304 Cylinder #4 Misfire.
  3. The engine is suffering a bonafide misfire condition, but no misfire codes are registered in the computer's memory (if OBD II equipped).
  4. Lack of power upon acceleration.
  5. Smell of unburned gas exiting the tail pipe.
  6. Rough idle and may stall.
  7. Cranks but does not start.
  8. Will not pass the emissions tests.
  9. Bad gas mileage.

What Causes A Misfire Condition?

Every cylinder, needs to have air, fuel, and spark to work. If any one of these components is missing from the equation, that cylinder will go dead. This means that so many different things can cause a misfire condition (or a rough idle condition). The cause of the misfire can be in any one of the following systems:

Ignition System: In a nutshell, the ignition system on the 2.3L Ford Mustang or Ranger consists of 2 ignition coil packs, an externally mounted ignition control module (certain years), spark plugs, and spark plug wires. The majority of misfire conditions have their root cause here.

  • Bad spark plugs:
    • Broken ceramic insulator.
    • Center electrode's gap is closed due to carbon build up (from oil burning within the cylinder).
    • Worn center electrode.
    • Carbon tracks on the ceramic insulator.
  • Bad spark plug wires:
    • Spark plug boot is torn.
    • Carbon tracks inside the boot.
    • The metal terminal that connects to the spark plug is missing.
    • Spark plug wire is so old that it's not transmitting spark anymore.
  • Bad ignition coil pack:
    • One or two towers (of the same ignition coil pack) are not firing off spark.
    • Several towers from different coil packs are not firing off spark.
  • Bad ignition control module:
    • The ignition module is not activating one part of the coil pack and the end result is two ‘dead’ cylinders (since each coil pack is made up of 2 individual ignition coils that feed two cylinders with spark simultaneously).
    • Not all 2.3L equipped Ford vehicles use an externally mounted ignition module, since in these vehicles, the PCM handles the ‘ignition module’ function internally.

Continued in the next page.

Ford Vehicles:

  • Mustang 2.3L
    • 1991, 1992, 1993
  • Ranger 2.3L
    • 1989, 1990, 1991, 1992, 1993,1994, 1995, 1996, 1997, 1998

Mazda Vehicles:

  • B2300 2.3L
    • 1994, 1995