Car cut off after redline

[EckOMaN2k]

Aight i was driving an my friend slipped my car into neutral when i wasnt paying attention, an we were at a redlight so then when it turns green i go to take off an my rpms go up an it redlines to like 7500rpm in my automatic.So then after that my car cuts off? I just put it into park an turn ignition all the way off then turned it back on an it started back up, then drove off. So can anyone tell me why this happend? Oh yeah an what are ka suppost to idle at like after car cut off an i put it into park id idled at 400rpms, then like regular idel is like at 700-900 rpms

P.S My motor is in bad shape anyway, my knock sensor is on, i need new o2 sensor, an i need to get a new timing chain kit thing installed. It has 126K miles on it, an oh yeah when i first turn on car like after letting it sit for like 6-7 hours it will start up an drop down to 200rpms then jump back up, then down then it will jump back up an stay at like 800rpms. I think that might be a leak in my intake somwere because one of my hoses is like all tight an no air barely gets threw it?

[240Knightrider]

Mine did that, I did an intake mod and now I have accidently Redlined it 3 times, the last one was teh worst, start to cut off then I let up. I normally drive by sound of my car if Im going fast and there is a lot a traffic around. I am still getting used to the new sound of the mod. Now my car is running funny at low speed like 2mph. Pretty much right when I start going. but it goes away