when i turn on the car, it goes up to about 1300 rpm and then it drops do like 200-300 rpm and then it will settle, when it drops it sounds and feels like it is going to stall, what is the problem?? my idle has also been kinda rough. the actual ignition os no problem its once the car has started.

 

could be your vaccum lines, i know some people with hondas with the same problem, not sure about nissans though, maybe the timing belt?

 

when was the last time you had a tune up? My car did the same thing and I gave it a well needed tune up and problem solved. I still have a slightly unstable idle but the stalling almost stopped and now idles between 700-800, But i just purchased a EGR valve and that hopefully should solve the unstable idle.

 

A tune up is a good bet for sure. Also, try some Gum Cutter or other form of throttle body cleaner too. You may just have excess carbon build up. All you need to do is disconnect the plumbing of the intake where it meets the TB, as the car is running......open the butterfly valve and spray for ten seconds. Close the valve and let the car run for a bit. Repeat this process over and over again until the can is empty. You'll actually see black smoke(the carbon) coming out of the exhaust. That may help you too. Try the little things first then move up to more expensive items.