its the bpt valve
you have to change th bpt valve, its a backpressure valve for the egr sytem. when the bpt valve leaks or is no longer good it hurts the idle and will somtimes kill the engine. dont forget to replace the 3 hoses attched to it they tear easily when you try to pull them out. you can also try testing your fuel injector plugs to see if they are gtting enough current. if they arent a lack of gas to the engine will also hurt the idle and kill the engine. if they arent provding enough current just buy ome wire and rewire the plugs jut before they join the main harness. a little bit of new wire does wonders.