My 1991 Regal, 3.1 lt automatic, has developed idle-speed Alzheimer''s. It cannot remember what rpm it is supposed to idle at; so, at a stop it searches up and down for the right idle speed and usually searches too slow and dies. It runs fine going down the road and seems to have more problem with this while stopped in gear as opposed to being in neutral or park. I have tried replacing the computer brain - no difference. Any suggestions?