2000 Ford Escort engine idles rough especially when in gear

I make sure that all vaccum hoses are ok. Changed pcv valve and connection; the previous pvc hose was soft and closing. No difference on the idling
Bot car @ 30,000mls. The idle w
as rough since then. The idle will cause the heater shield over on the exhaust to clank loudly.(I may need to secure it with wrapping it with a wire or take it off).
I had 3 escorts the past 10 years and all had the same idle problem. I accepted the irritation. The mechanic could not find the problem.I usually put gear to nuetral at a stop light or sign; I could not stand the vibration. Occasionally the engine will go off if not put in nuetral when stopped.