Check engine light on RPM's are going crazy and idle is rough

What was the code or codes that came up from the engine light? High rpm and rough running that seems to get better at higher rpm sounds like a vacuum leak or lean fuel condition. I would look for a bad hose or leak around the intake system. Also, check that the throttle body is clean and the IAC system is working as it could stick open and let in extra air which will also cause a higher rpm.

Okay, the rpm signal comes from the ignition control module. Check the wiring to it for corrosion or a bad ground. That could cause jumpy rpm. I would still look over the throttle body as well, if the IAC has an issue it could be causing the rpm's to fluctuate as well.