One thing everybody here has missed, and is common with the 3.5L. The
intake manifold gasket develops a leak, (around cyl 5 IIRC) which causes
loss of vacuum, rough idle and sets the CEL. The ingition
ON-OFF-ON-OFF-ON sequence will most likely reveal error code 43.

DudLee Brennfoerder wrote:
> 1996 Chysler Concorde
> 3.5l
> Friends daughter is coming home from
> school this weekend, and wants help with her car.
> Check engine light is on...
>
> Runs great at any driving speed, but at idle - in park or
> neutral, it runs extremely rough.
>
> Car has 60k miles, and is MINT!
>
> I am having thoughts or:
> 02 sensor
> fuel filter
> spark plug
> air filter
>
> but unsure what to have on hand when she gets here---
>
> IDEAS?
>
> email me:
>
>