4lb when hot, jesus that's low, I'd swap the oil right away, is the car high mileage ?, may just be getting very worn or shit oil, try a thicker grade ie a 50 instead of 40 etc if it's got loads of miles on it, will help the pressure problem, don't need a huge amount of pressure at idle anyway, but wouldv'e wanted higher than 4lb idleally.
tabetha