hey i just bought a 2000 acura integra gsr.. it was running fine when i bought it, but recently whenever i am in neutral or have the clutch engaged, the rpms constantly rev between 1.5, and 2.5k rpms.
sometimes when i first start it up, it will idle really high, at like 3k, but as the car warms up, i give it a little gas and it starts fluctuating again.

if you know of a common solution to this problem please let me know, thanks.

 

Just change your IACV.

Thats the issue I had, its just unable to regulate idle speeds because of well, any number of things. Its rare they go bad but when they do its a pain.