Chrysler Repair: 96 Plymouth Breeze, plymouth breeze, accurate count

Question
I am wondering how to fix a rough Idling 1996 Plymouth Breeze. it is 2.0L. The car will Idle roughly while just sitting at any given stop but the car drives perfect when in motion. There are no hiccups or anything with it when I drive. I also have an issue with the CE (Check Engine)light. A friend and I have changed oil and air filters, plugs, water pump, power steering belt, and timing belt in the car. when we put it back into time,  the CE light went off, but shortly after driving it again, the light came back on. it couldn't of gone out of time that fast again, could it? any help greatly appreciated.

Answer
I would try using the ignition key to get a fault code readout:"On-off-on-off-on and leave on" doing that in 5 seconds or less elapsed time. Then watch the check engine light which remains "on" to begin to flash, pause, flash, etc. Count the number of flashes before each pause. Then repeat to be sure of an accurate count. Then group the numbers in pair in the order of appearance to form the 2-digit fault codes. Then go to www.allpar.com/fix/codes.html for a code listing.  Then write back and we'll go from there.
Roland