How to Check the Spark Plugs in Your Ford Engine

As durable as spark plugs are, they all fail eventually. It’s because the conditions within the combustion chambers (where the spark plugs are located) are extremely harsh. Spark plugs are continuously subjected to high temperatures and vibration. This causes some issues like:

  • Carbon buildup
  • Erosion of the ground electrode
  • Worn or loose spark plug cables

In this guide, you’ll learn how to inspect your spark plugs and tell a bad one from a good one.

Warning Signs of a Bad Spark Plug

Old new plug

Knowing the signs of a bad spark plug will allow you to identify it and replace it as soon as possible. If your Ford engine starts to show at least one of the following symptoms, you may want to look at your spark plugs.

  • High fuel consumption
  • Sluggish acceleration
  • Engine misfires
  • Rough idle
  • Trouble starting your car

How to Access Your Spark Plugs

Got a hunch that one of your spark plugs has gone bad? You don’t have to pay a Ford dealership for an official diagnosis. If you have a spark plug socket and other basic tools, you can certainly check your spark plugs at home at no cost. First, you need to access the spark plugs. Below is a list of steps on how to do this. Keep in mind that we based these instructions on the Ford Focus, but you should be able to follow it with most of the other Ford models.

  1. Make sure your engine is cool to the touch.
  2. Disconnect the battery.
  3. Open the hood and then find the ignition coils.
  4. On one of the coils, push the tab on the harness and then disconnect the harness from the coil.
  5. Unbolt the ignition coil with a socket wrench and then remove the coil.
  6. With a spark plug socket and an extension, remove the spark plug from the cylinder.
  7. Examine the spark plug.
  8. Repeat with the rest of the spark plugs in your engine.

What to Look For

It’s pretty easy to identify a bad spark plug. Basically, cracks, erosion, or melted spots are clear indicators that the spark plug has gone bad. You also want to look for black soot or oily deposits anywhere on the plug. Excessive erosion of the ground electrode (the hook-shaped part at the bottom of the plug) is another big indicator of a bad spark plug.

Replacing Your Spark Plug(s)

OEM motorcraft plug

Spark plug replacements are so easy that you can do it at home. The process is almost exactly the same as the diagnostic process outlined above. Except you put in the new spark plug instead of the old one. Here’s a thorough tutorial on replacing your spark plugs.

Have any questions about accessing your spark plugs and identifying a bad one? Our trusted and knowledgeable staff is here to help you every step of the way. Contact us to chat with one of our experts!