Sounds like the battery might have been disconnected or run dead recently. If so, the Engine Computer lost its memory and has to relearn "minimum throttle" before it will know when it must be in control of idle speed. It also might not give you the normal "idle flare-up" to 1500 rpm when you start the engine. To meet the conditions for the relearn to take place, drive at highway speed with the engine warmed up, then coast for at least seven seconds without touching the brake or gas pedals.
There could also be a problem with the automatic idle speed motor. As long as it is okay electrically it won't set a fault code, but if it is sticking or the air passage is blocked with carbon, it won't be able to adjust idle speed properly. The clue again is no idle flare-up to 1500 rpm when you start the engine. Your mechanic can confirm that by connecting a scanner that can raise engine speed in 200 rpm increments to see if it responds. Not all aftermarket scanners can do that so you might need the Chrysler DRB3 scanner. Many independent shops have them because they will work on other brands of cars too.
Monday, April 11th, 2011 AT 7:24 PM