I have a 2005 Eclipse GT and when the car is stopped and idleing the RPM's will bounce between 400-1000 Rpms and it will change from 400 to 1000 Rpms and back at least once a second. im not sure what is causing this problem. I know it is not a missfire, because i just fixed a 6th cylinder missfire and its not even close to sounding like that. A friend told me his civic (i know its completely different) used to do that and it turned out to be a idle control valve? I'm not sure if that could be, any suggestions will help! thanks.

 

i also had a problem with my eclipse.. the same problem you had i looked it over and i found one of my spark plus wires was messed up melted down and crap so i changes it and it fixed it

 

you also might try tuning your idle to i had to tune it myself when i put my intake on