I have a 1996 accord. the attached photo shows a plug located in the back left of the engine area. Anyone know what it is for or where it plugs in to?

 

Looks like the VTEC solenoid valve.

 

Does it have a home, and would it affect the idle?
My accord likes to go from 1000 rpm to 1300 rpm every 2 seconds.
It would be great if I just had to plug this in and it's fixed.

 

Look for another connector plug on a wire harness. See pics.

The VTEC solenoid control valve being unplugged probably doesn't have anything to with your idle problem. Generally, that affects the valve timing change at higher engine speeds (around 2,300 - 3,200 rpms, depending on manifold pressure) and under other conditions.

Your idle problem may have to due to the idle air control valve or something else. See the Common DIY and Info. Thread sticky at the top of this forum for a thread on the IACV cleaning.