1985 190D missing at idle and excess blowby

About a week ago ,I was driving home from work. My house is at the top of a hill and makes the engine pull pretty good on my way up. Just as I pulled into my driveway to park, I noticed that the engine was missing fairly steadily at idle. It had never done that before and because it's a diesel, I became quite concerned. I opened the hood with the engine running. I noticed alot of blowby coming form a small hole in the side of the valve cover. I then took the oil filler cap off and observed what seemed to me to be excessive blowby and oil being blown out of the engine. I decided to drive the car to work the next day. I commute about 85 miles one way. When I got to work, I noticed oil seaping around the filler cap, the crankcase vent hose inlet and that small hole in the side of my valve cover. The engine was also still missing at idle. One thing to note is that the engine seems to run fine with plenty of power once rpm's rise above about 1500. You can actually hear the missing cyclinder kick in and start to fire above that speed. I have also observed that when cold, the engine's exhaust gives off lot's of blue smoke which seems to subside once it warms up and cruising down the road. Also, the car has been using about 1 quart of oil to every 600 to 1000 miles which obviously is excessive. I suspect either bad valve stem seals, a broken ring or may be a small hole in the piston. Any other ideas or feedback would be appreciated. Thanks. Chris

maybe carbon sticking on a valve... unfortunatly not easy to check.