My Civic Idles odd, im not quite sure what it is.
when it idles, it will rev up and down constantly and eventually stop.
i think it may be the ecu, but im not completely sure
What do i need to do?

 

Clean your iacv there is a thread in the faq's showing you how to

 

what he said. Also try using a vacuum guage on it to see if there is a big vacuum leak somewhere. I had that same problem and it turns out one of my valves was lashed wrong. The vacuum guage and cleaning the IACV is a good place to start.

 

just the iacv dude....

 

How about tell us what car? An FITV might also be involved.
How do you people diagnose without knowing what car we're even talking about?

 

Try cleaning throttle body, clean IACV and if you have a FITV clean that out to.