you can test the voltage drop across the coil. don't ask me how, cause for the life of me i can't remember at the moment. brain is running rough, just like your wife's car.
electricity will find the path of least resistance and follow it every single time. if the problem is with the coil, say maybe it's worn in a spot (weak spot or something), the juice that should run through the wire could actually arc to the block. you'll still get some juice through the wire, but not all that's intended to be there.
don't quote me on this, i could be wrong. i believe to test the voltage drop, you take a multimeter and put one lead on a coil point and the other to the battery, i think to the negative terminal. you do this with the ignition on but car off. check each point. should be looking for around 12V at every point. if it's a multiple coil pack, you replace the bad pack. if it's one big coil, you replace the entire coil.
i'm pretty sure that's how you check the coil. like i said, my brain is running rough tonight. too much other shit on my mind.
good luck, and, uh, don't buy another ford
