Hi I have a 1997 Honda civic that I just bought. It started Idleing in park from 1000 RPM's to 2000 RPMS on its own back and forth. If I put it in drive it drops down but I have felt some pulling of the rpms when driving and I let off the gas. Is this the Idle sensor and where is that located. Thanks in advance Mark

Replace the Ignition Control Module:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-46563-4.html#post265896