My '91 Ls rear suspension seems to air up and deflate at will. It will hold air when filled and parked. When driving or parking at certain angles it will deflate. I also noticed the switch will not work at times to go from norm to high. It usually does not work after it has deflated (only the rear). If I disconnect the negative terminal from the battery for a few minutes it will air up and the switch will work again. Sometimes it will stay and sometimes it won't. I know there isn't a leak because it will stay aired up while parked for a couple of days. Is there some kind of sensor that may be causing this?