How Tos / Tech

A Guide to Reading Spark Plugs

Your spark plugs are like a cipher.

And to read a cipher code, you usually need a cipher key. That’s what this is—a cipher key that is going to help you “read” your spark plugs and understand what they’re telling you about how your engine is running.

Is your engine running too rich? Too lean? Could there be a problem with ignition timing, or your oil system?

The answers are often in your spark plugs, and by using this chart to diagnose your engine’s performance, you’ll be able to make whatever adjustments might be necessary to achieve peak performance.

(Image by OnAllCylinders contributor Lori Sams)

(Image by OnAllCylinders contributor Lori Sams)

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4 Comments

  1. Evelyn Ruehr says:

    Good morning, I am and I live in Veneuela, I would like you to inform me if they have and the cost of Bujias for a FX4 FORD 2008 2008 minivan cab and half motor 5.4. SP 515.
    Thanks greetings.

  2. Pingback: Mailbag: Tracking Down Common Causes of Sluggish Engine Response - OnAllCylinders

  3. JOSE RIVERA says:

    que pasa si la calibracion de las bujias de mi auto es 52 a56 y me las calibraron a 35 gracias por atender mi pregunta buen dia.jose

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