My 87 260E has an extremely eratic idle. Even when it is cold or warm. When it is running sometimes it runs o.k. and other times it is barely running at about 500rpm and it stalls sometimes to. If I let it run at 500rpm it will eventually catch after several minutes and run smoothly. When I start it the same thing happens, it will barely run at about 500rpm and after a few minutes it will raise to a normal cold idle. Does anyone know what I can try to do to fix this.