How to Test Spark Plug Wires

Austin, my Ford Mustang has an intermittent engine miss that I can not figure out. I replaced the spark plugs, air and fuel filters but it still does it. My spark plug wires look good, and the ignition coil seems to be ok.

Could a bad computer cause an engine miss sometimes? It seems to really do it when I am heavy in the throttle, so its hard to test when I get back home in my garage.

Hey Wilson,

I have told you guys this in the past…my “secret” shade tree test for determining bad spark plug wires on your car, but I was finally able to catch the whole process on video to share.

There is no audio to the video below…but it was just a bunch of mechanics standing around saying “cool……..that’s cool……do it again Austin…”

So here is the skinny again: If your car is experiencing an engine miss (engine miss – meaning a jerking feeling or shutter from the engine as you accelerate or a shake or wobble feel coming from the engine while at idle)

Grab a water bottle sprayer and add a little regular dish soap and water and spray the spark plug wires WHILE THE ENGINE IS RUNNING in park. If the soapy water mixture finds a hole or soft spot in the spark plug wire the spark will jump out of the wire and ground itself to the water.

The engine will really miss and run bad once the spark comes out of the water. If you see the spark come out of the wire or the engine begins to run rough and miss when you spray water on the spark plug wires….you need new spark plug wires!

Do NOT use a flammable liquid to do this with, since the spark will come out of the wire…you will have a fire under your hood if you use anything flammable. Also DO NOT spray this soapy water mixture on any electronics or sensors under the hood…distributors and distributor caps included.



Austin Davis

About the Author:

Austin Davis, consumer car repair advocate. "Hi there! I love to help people solve their car repair problems and I hope my site was helpful to you today. Thank you for stopping by."