E36 and E34 electrics questions????

Both my e36 and e34 are reving wierd wen in neutral, they go frm bout 900 te 400 revs??? Is this jst a sensor or sumtin????

And on me e36 coupe the windows are automatic but wen their coming up automaticly they hit a point and go back down, ive checked if their catching off anything but their not, anyone no what the problem is????

Any1 good with the bmws, its wreckin me head!!!

e 36 usually do it when theres an air leak (intake rubber split)
possibly same for the e46 although could be afm :)