I have something shorting out under the car. what could be shorting under the engine and killing the engine

I have something shorting out under the car. when i move the wire harnesses that run under the engine the shorting stops for a while. it started just killing the engine at a slow turn or just before stopping. now it was making the car chug and jurk and the rpm guage to jump spiratically .when i moved the harnesses it stopped again. I have had to replace the feul pump the ICM the ECM and a mutlitude of other parts under the hood. when i took the car stereo out, the black wire on the harness and the connector were melted (the wire some but the connector massive)which i replaced.so i would assume something is shorting directly to the ground.the car runs like a dream and the guy before me put $800 in parts under the hood. I have just figured out that it stops after moving the wires but not sure which ones.