If the battery was recently disconnected or run dead 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. The engine will be hard to start unless you hold the gas pedal down 1/4". It also might not give you the normal "idle flare-up" to 1500 rpm when you start the engine, and the engine will want to stall when coming to stop.. 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.
The rough running adds another dimension to this. Your idle control system is very similar to the Chrysler system. Those have enough control to keep a V-8 engine running with six dead cylinders, (obviously not smoothly). If you feel the rough engine, you have a misfire that must be addressed first, unless it is running rough because the idle speed is just too low.
Oct 5, 2013 at 12:28 AM
