A few crossed wires here I think.
You need to state the motherboard. Haven't got a clue what 4 pin power plug you have pulled. It could be the front switch header, the CPU power, the side piece on the 20/24 pin main socket, a GFX 4 pin, a hard drive 4 pin ....
And I don't exactly know what the problem is here. You seem to state that 'the motherboard powers up on its own'.
Why is that a problem?