man i had both of these problems my friend. first off check all the connections and leads to and from your battery to your alternator. i replaced my alternator after having my old one rebuilt which didnt do anything... but as far as the idling problem... my engine used to shake like crazy at idle. i did many things...including a head job and nothing worked...then i randomly changed my fuel injectors like 3 weeks ago...and boom all better....its kinda of expensive but it worked wonders for me. lost the shake got better acceleration and stuff.. so yea fuel injectors fixed it for me.