Originally Posted by Nitramjr
Welcome to FTE.
If I had to guess, I would say that your brake hiss and your rough idle may be related. Your power brake booster may be shot which is causing a vacuum leak and the vacuum leak may be causing the rough idle.
Without driving the car, disconnect the vacuum line to the brake booster and plug it. Then see if the hissing sound and rough idle go away.
You may also want to put a vacuum gauge on the engine to see if there is a difference with the brake booster hooked up versus disconnected.
Thanks for the welcome. I changed the idle air control valve early this morning (before I read your reply) and it seems to have fixed the rough idle. The ride is much better however, he true test for the IAC valve will be tomorrow morning once the car has cooled over night.
I am interested in trying your vacuum hose suggestion. Is this something that I can try on my own or is some knowhow involved.
Thanks again....
I will keep you posted.