dorkpunch

So while driving down the road yesterday, my mustang suddenly lost power and started to pop and sputter, almost like it ran out of gas. I suspected the plug that goes into my coil pack, because the clip on it is broken and it has wiggled itself off once in the past. It seemed okay, but I wiggled it and the car started and ran fine. For about 30 seconds. If I kept the rpms above about 2.5k, it would run okay. Any less than that it would drop down to about 500 rpms, chug and sputter, then die. Wouldnt restart until I wiggled the coil pack wire again. After mucking around some, I figured out that if I unplug the little black box next to the coil pack (about the size of a postage stamp but about 1/4" thick, two wires going to it out of the back of the coil pack wiring), it would run fine.

What the heck is this part? Am I going to screw anything up leaving it unplugged?