Have a 2005 GP Base model, 3.8 L with 112,000 miles. Engine misfires when it is warm, shut down or sits for a minute or so then restarted. So when driving at low speed cruising is is misfiring or "skipping". BUT if I turn the engine off and restart, going down the road, it starts and runs fine. This event is inconsistant. New Autolite double platium plugs with Bosch wires at 96,000 miles. Scanner says no codes!. Thanks