Problems with Neon Chrysler

Greetings to the mechanics community. Here looking for their close suggestions. I tell you my problem:
last week my car began with the following problem, from nothing stops and I give it and immediately turn on again. Well this problem disappeared, all good. Well today I felt that I was in a tranque and began to accelerate a little, then it went down to its normal revolution. Now he is stopping again, but as I comment, he turns on immediately. I have been using 91 Octanos for years, although the 95 octane is specified. In my ignorance I think it will be the catalyst that is obstructing the normal exit of the gases.
I thank you in advance all the help you can offer me.
Your friend
Edwin

Hello friend, I recommend you review the IAC which is responsible for the idle. (Because he goes up and avesses, the car goes out) The catalyzer is not because there loses the car forces at first and when it is advanced you start and turn off in a few seconds. I recommend an ABC with a mechanic. Greetings Bernhard

Thank you friend Bernhard, surely your contribution will be very useful. Just tell him something else, today I use it and diagnose that only that happens when I put neutral (n), because if I keep it in this age of standing it does not happen. My transmission is automatic. So I think like you who is the diagnosis that you point to IAC. Well, very grateful.
Edwin