Ford Mustang repair
If its really turning and not unthreading you have a stripped plug. If you can gasp it with long needle nose type pliers try that buy some if necessary. I start the engine and rotate the plug the pressure will force it up and assist blowing it out / clear Don't do this if your not comfortable or know how safely work in this manner.. i.e. proper gear and technique. Its potentially a projectile KNOW this. Or pay and have it done.
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