Misfire Troubleshooting Tutorials

OK, so you've found the dead cylinder on your Ford 5.0L engine (or 5.8L engine), what's next? Well, the next step is to find out what's causing the misfire (miss) condition.

There are several problem areas that you need to test and these areas are:

  1. Ignition System. For example:
    1. Bad distributor cap.
    2. Bad spark plug.
    3. Bad spark plug wires.
  2. Fuel System. For example:
    1. Bad fuel injector.
    2. Fuel injector not being activate by PCM or due to a short in the wiring.
  3. Engine Mechanical. For example:
    1. Low engine compression.

Don't let the above list of problem areas discourage you, because the most important thing you've done (to narrow down rough idle-‘dead’ cylinder issue) is knowing which cylinder is the ‘dead’ one.

I'm gonna' offer you my diagnostic strategy, which will further aid you in finding the root cause of the misfire on your Ford 5.0L engine (5.8L engine).

Here are my suggestions (and the diagnostic strategy I use):

  1. Test the ignition system first.
    1. The ignition system is usually the culprit behind most of the misfire (‘dead’ cylinder) conditions.
    2. You can find an in-depth tutorial on how to test the distributor cap and spark plug wires here: How To Test The Ford Ignition Control Module (at: easyautodiagnostics.com).
  2. Test the engine compression second.
    1. After making sure that the ignition system is providing spark to the ‘dead’ cylinder, the next step would be to check that cylinder's compression.
    2. You can find an in-depth tutorial on how to test the engine compression here: How To Test Engine Compression (4.9L, 5.0L, 5.8L).
  3. Test the fuel injectors last.
    1. After eliminating the ignition system and the engine compression as the cause of the misfire, the next step is to make sure that the fuel injector is not fried internally.
    2. You can find an in-depth tutorial on how to do a fuel injector resistance test here: How To Test The Fuel Injectors (5.0L Engine, 5.8L Engine).

The above list of tests can be modified to suit your particular diagnostic, troubleshooting needs (since there really isn't a specific cookie cutter way of diagnosing a car).

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Ford Vehicles:

  • Bronco 5.0L, 5.8L
    • 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996
  • Crown Victoria 5.0L
    • 1989, 1990, 1991
  • E150, E250, E350 5.0L, 5.8L
    • 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996

Ford Vehicles:

  • F150, F250, F350 5.0L, 5.8L
    • 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997
  • Mustang 5.0L
    • 1988, 1989, 1990, 1991, 1992, 1993
  • Thunderbird 5.0L
    • 1988, 1989, 1990

Lincoln Vehicles:

  • Continental
    • 1988, 1989, 1990
  • Mark VII
    • 1988, 1989, 1990, 1991, 1992
  • Town Car
    • 1988, 1989, 1990

Mercury Vehicles:

  • Cougar 5.0L
    • 1988, 1989, 1990

Mercury Vehicles:

  • Grand Marquis 5.0L
    • 1988, 1989, 1990, 1991