Okay, I threw a code today after bringing my car down off of ramps to check for leaks. (unrelated to each other, I know...) It ran horrible, like it only had 2 cylinders or something. I popped the hood and found my coil harness to be loose. I also found the connector clip to be broken. I pushed it back on and it ran fine for a while, then it started acting up again and threw the same code. I checked the harness and it didn't feel super loose, but it's not "clicked-in" tight either. So, what's the chance it's only the harness and not my 2 year old accel super coil?

 

Get a new connector end that's not broken. You should be able to get just the one connector from Ford and just cut and splice it in.

If the connector isn't clicked in, the terminals are most likely not making full contact, which is causing your problem.

Once you get a connector see if it still does it. I might be the accel coil, though. They aren't exactly the best out there.

 

Yeah, those clips are easy to break if you aren't careful. If it runs ok for a while pushed all the way down, it's wiggling it's way loose as X has said, bad connection. Call ford or junkyard possibly, or if you have a mustang wrecker near you like I do, all the better. I'd say the coil is probably fine if it's only two years old.