the only way to do this yourself (that i know of) is to pull each coil out, and see if its sparking, you will see what looks like a lightning bolt. make sure if you do this, to use rubber handle plyers to hold the coil. because your body is a ground, and it will jump to the closet grounded point, so stay several inches from the bottom of the coil tube. i would just hold it a few inches off the spark plug with the car running, and see if its sparking regularly. you should see the spark jump from the coil to the plug. if not, they are only $50 at a discount import parts store, thats what i got one for when i broke one. BE CAREFUL with them, i broke one, they are fragile, more than you would think.