P'cola FD

Crap! Just recently my car has been acting a fool. The check engine light comes on and off repeatedly and violently jerks the car when it does. When the light is on it seems to be in limp home mode. When the light is off it is totally normal. The problem is that it comes on and off and bucks like a bull.
I checked the check engine light codes(properly) but nothing came up.
So I decided to try my friends power fc. The results were confusing to say the least. When the check engine light flashed, it did one of two things: either show a black box around the water and air thermosensors, or (now this is weird) restart the ecu. It was like I turned the key on and off really fast, but the engine was running. I'm pretty sure it is a short somewhere, or something along those lines, because going over rough bumps changes the status. I might just get a new wiring harness(or used if someone has a good one), but what else could I check? Why would the ecu be flicking on and off like that?
Thanks for any help you guys can give me.
--Danny

GsrSol

Defiantly sounds like a short or loose wire. Problem is finding it. Could be at the ecu, fuse boxes, or ignition.

I would first check the fuse boxes under the hood, if you haven't already since your last thread.