Engine idle too low. Stumbles sputters on startup after sitting overnight . rougher idle when ac is turned on while ideling it fluxuates when clutch o

I have a 2005 ford tauras 3.0l v6 auto ohv engine . Sometimes on start up car stumbles and sputters for 2 or 3 seconds or if you hit the gas pedal right away it clears up immediately. But once car runs for a minute the idle drops close to 550 to 650 rpm and kind of barely fluxuates. Then if you turn on ac before driving it bogs down for 2 seconds and causes a rougher idle condition.no check engine light is on. It just seems it should be ideling around or close to 1000 rpm not 500 to 700 rpm. What are your thoughts?