Dodge Repair: IDLE OFF, rich mixture, sensor circuit

Question
Hi;
    Hope you can help me with this issue. My brothers '97 Neon with the SOHC motor began idling rough. When the car is idling it lopes as if is gonna shut of than it revs up and stabilizes for few minutes than it repeats the same low rpm,high rpm idling. I had a friend retreive the codes and i got
1) po171 system too lean
2) p1899 park neutral switch stuck in park or gear
3) p0443 evap control system purge control valve circuit malfunction
4) p0137 02 sensor circuit low voltage bank1 sensor2.
   About 4 months ago i replaced the o2 sensor at the downstream location.The back up light switch was also replaced a year ago,these were fine until a week ago,is it possible that the evap is responsible for all these ills?

                                Thank you
                                  Tom s.

Answer
Hi,
It's possible that it is caused by the module that plugs into the evaporator.  However, I would check to see that the EGR valve is working properly.  This will cause a rich mixture and rough ideling.  It will also cause false code readings.

Cowboy 1104