idling problems, 2003 eclipse gts?

Have you had the valve clearances adjusted lately.
If so it is possible they may be set too tight.

Check vacuum hoses around inlet manifold.
You will find that one has either come off or is cracked & is sucking in air causing it to run lean.
When it is cold the the temp sensor tells the computor to run rich which covers for it running lean.When temp sensor hot (reverse happens)there is not enough fuel to air ratio causing it to miss(run rough).

HadafewDees&Gses
August 2009