Problems with Neon Chrysler

Greetings to the mechanic community. I'm here seeking your insightful suggestions. Here's my problem:
Last week, my car started having the following issue: it would stall out of nowhere, and when I tried to restart it, it would immediately start again. This problem disappeared, and everything was fine. Well, today I noticed it was stuck in traffic, and it started revving up a little, then it would drop back to its normal RPMs. Now it's stalling again, but as I mentioned, it restarts right away. I've been using 91-octane gasoline for years, even though it's specified to be 95-octane. In my ignorance, I think it might be the catalytic converter obstructing the normal flow of exhaust gases.
I appreciate any help you can offer.
Your friend,
Edwin

Hi friend, I recommend checking the IAC valve, which is responsible for the idle speed (because sometimes it revs up and sometimes the car stalls). It's not the catalytic converter because that's where the car loses power at first, and when you accelerate, it stalls after a few seconds. I recommend a thorough inspection by a mechanic. Regards, Bernhard

Thanks, Bernhard. I'm sure your input will be very helpful. Just one more thing: I used it today and found that it only happens when I put it in neutral (N). If I keep it in drive (D), it doesn't stall. My transmission is automatic. So I agree with you that the problem is the IAC valve, as you suggested. Thanks again.
Edwin