took my 87 420SEL to a local repair shop and they said my Idle air stabilizer valve wasnt working...I havent seen that listed in any parts books..any ideas what they meant?..i did ask them and they said it did the obvious..controled the idle speed and how it runs at an idle.....they said 240 bucks parts and labor...which they said the part listed for over 500 bucks but they get a good deal on them...wonder what that is..