Hi. I've had this problem on and off for a while now, but it's getting to a point where I'm getting annoyed with it.

The car's idle revv counter doesn't seem right, i'm not sure if it's an air problem or a sensor issue.
Whenever I knock the car out of gear and coast to a red light or any stop, the car stalls. The revvs go down to <600, the battery warning light comes on, and stalls. If i'm quick enough i can give the car a touch of gas and it stays running, and the light goes out.

I've just replaced the crankcase vent pipe because that popped the engine management light on a few weeks back. I'm not sure if these 2 issues are related.

A friend of mine mentioned it could be an air intake issue, or there's a problem with a fuel sensor. But i'd rather have the opinion of someone more specialized.

Thanks in advance

P.S Can you dumb down your responses for me