low idle from time to time

[NC325iC]

ok this is a reoccuring problem
from time to time my car will idle really low (~500rpm) and rev to about 700rpm then return, repeat over and over
it gets rather close to stalling
it has happened recently after disconnecting the battery, and it happened after my old battery died, but sometimes it just randomly happens
anyone know what it could be?

[92 mtechnic cabrio]

if you didn't mention the battery, I would've mentioned the TPS

[Axxe]

I had the same problem. Turns out the TPS screw was loose and vibrating around, so I just tightened it back up and everything is good now. BTW it's underneat the TB, I found it easier to remove the TB and clean it at the same time.