well my dad has a lexus ls 400, it has been siting in our garage for 1 year, so when we decided to drive from arizona to california last week, we decided to go on it, so we drove it about 20 miles in the phoenix area to make sure it was working properly, then it ran OK for about 100 miles, then we were on the freeway, and the RPM suddenly started getting lower, putting an impact on the speed, then when it almost touched 0, it suddenly shot up to 1.5, we had to end up getting it pulled over, and it wouldnt start, then we waited for a half hour and it started, then we drove it to a city and it got bad again, we showed the mechanic, and it also does this when it is in park, but the mechanic said that it is probably a sensor because lexus is computer controlled, but no mechanic was able to repair it, then my dad turned the trac controll off and it worked fine till today, l dont think it got fixed because of the trac controll , what could have caused it
the hood also got closed shut by the wind when it was open from the wind, and that may have affected it, by moving around some parts

sounds like a computer problem