stalls on neutral

hello, ive asked for help around quite abit but still cant find the solution...

my car has weird idle everytime i hold and release the brakes, the rpms would drop and make a "rumbling" sound and sometimes stall in neutral.
it stalled on me like 6-7 times today driving home and im really annoyed...

someone said it could be a bad cat converter and i did have a bad cat... changed the cat and the problem still exists...
when i was ficing my cat, the mechanic said my o2 sensor may be finished also so i might need a new one...

well back to the stalling in neutral, i asked someone and they said it is a vacuum leak somewhere and i should find it... well i dont know where to start on this

another person told me to adjust the idle speed yet i have no clue on the proper way to do this...

anyone else know any reason why my car is stalling in neutral + the solution to fix this problem?

thanks

I get the same problem every now and then, but I have not been able to find what or where the problem is. Vacuum leak most likely.

this also happens only when the engine is warmed up and typically happens on hot days...
problem gets worsts day after day
weird feeling when your car dies driving 50 mph on the road and a car is in front of u...

i have the same problem happen to me. it only happens in neutral. My car idles very funny also. sometimes it idles @ 1200, others it's somewhere around 750. Sometiems it even goes to zero without the car shuting off, and then just jumps back up again, when this happens i can feel a jerk in the car. Haven't talked anyone about it, because it just started happening two days ago and i've been too busy working. When someone finds out what this is, please let me know.

How do the breaks work? Spongy at all? You could have a small leak in the brake booster hose. That would cause it to idle funny. Check other vacume hoses as well. The pcv valve is a cheap item. Pull it up and shake it to see if it rattles. My guess is vacume