I bought a 91 Accord EX Station Wagon at a police auction a few months ago. Put a new battery in it and it started right up. The only problem is the idle instantly shoots to 3k then drops to 1.5k then shots back up to 3k and drops. This is just constantly going on the entire time. Like a ghost is revving the car haha.

Anyways, aside from a exorcism what else could fix this?

 

Either bad egr or worn vac lines and u need to replace. I would do both n full tune up

 

As suggested by others. You can also check the FITV, after you'e confirmed the coolant is full.

 

Air bubble in coolant = Bleed coolant
Vacuum leak - rotted hoses / gasket = Check for vacuum leaks
Dirty IAC valve = Clean IAC valve, throttle body & Intake manifold
Improperly adjusted FIT valve = Check adjustment of valve

There are two very descriptive threads in the FAQ that cover surging idle issues.
Cleaning the Intake air control valve (IAC) & throttle body
Fast Idle thermal valve (FIT) adjustment