idle speed


hello its me once again and i know i do ask a lot but unfortunately this is the only site that can realy answer my questions and realy knows about daihatsu rocky. as i mension before i currently have a 1986 daihatsu rocky 2.8 diesel non turbo and i dont know if its normal or there is something it needs to be fixed. when i turn my engine on at regular idle speed the engine sounds like is accelerated and it fact it is because inside in the tachometer it reads just a little less than between the 1 and 2 but than again it drops its idle speed to a little over than between the 0 and 1 and it drops the engine stars shaking to a point that it almost shuts off or maybe it will if it goes a little more and it does that every time and not only when the car is sitting still but also when i am driving and i down shift. i dont know if i explain my self correctly but please let me know so i can explain it better because i realy need help with this because i am almost sure that there is something that needs to be done. thanks and would realy like to congratulate you all for answering my questions and keeping this site up. thanks again.