Chrysler Repair: 2002 Dodge Neon: rough idle, dodge neon, computer settings

Question
I have a 2002 Dodge Neon with a 4 cylinder, and an automatic. I have a rough idle when in park, neutral, drive and reverse. When the compressor kicks in it gets worse. The vibration varies from time to time, by varying I mean that it is worse than other times, at its worst you can actually see the steering wheel moving not just feel it. It has had a tune, oil change, I was told by a friend that it is in the computer settings and that dodge can change them. Is this true? There are no codes in the computer, to my knowledge it has never been overheated. What else can cause this, and how do I fix it?

Answer
Hi Lawrence,
I find it hard to believe that there would be no trouble codes stored in the memory of the pcm.
Try the ignition key:"on-off-on-off-on and leave on" doing that in 5 seconds or less elapsed time. Then watch the odometer window to see the mileage reading change to show any 4-digit number preceded by a P or a "done". Let me know what happens.  Without a code there is little I can recommend at a distance other than to clean the throat/ both sides of thebutterfly valve/side air passageway of the throttle body.
Roland