I have a 2002 S80 2.9L non turbo that when I first start the car it jumps to 2000RPM and then after about 2 minutes it drops down to about 900RPM. But lately when the gas level gets down to a little over 1/4 of a tank or less the RPM's drop down to about 500. I have had the fuel pump replaced per the recall and the spark plugs and coils are all less than a year old. I can't figure out if this is normal or if there is something wrong but I don't remember the car doing this when I first bought it 4 years ago from the original owner. Also not sure if this has anything to do with it or not but the A/C works for about an hour of highway driving and then seems to freeze or something because it will not blow cold air any more until I turn off the A/C for about 30 minutes or more. Please help with anything you can think of, I need this car to just get me through another 2 years of Med School before I can get something else. Thank you for all the help in advanced.
Thanks,
Kate
P.S. the car has 176K miles as of right now and most of it is highway driving.