Hello all, was wondering if anyone can help me with an issue im having.. My 79 450SL idles around 1200rpm's while warming up..Takes like 30 minutes of running for it to come down..I have been putting air conditioning on just to kick compressor on to slow it dow so it dont slam into gear.. I tried adjusting that big white nylon looking scew but I can actually screw it all the way in without much effect on slowing down idle..Is there an idle speed control or something in this car? Am I supposed to be able to stall car if that white screw is turned all the way in? If so what would I need to replace in that instance? Thanks for any and all suggestions...