Arcing across coil terminals

Do this test and if it is good I would change the coil wire at least the boot on it.
This testing procedure is valid for just about any automotive coil. Using an ohmmeter, check the resistance between the side terminals of the coil. Do this with all of the wires to the coil disconnected. You should see 0.75 to 0.81 ohm of resistance. Then check the resistance between either side terminal and the center high tension terminal. The reading should be 10,000 to 11,000 ohms. Any significant deviation from these numbers would indicate that the coil is defective.