My 1984 190D 2.2L sounds like it's missing on one cylinder, there is a chuffing sound coming from the tail pipe. There is also a knocking sound that is most easily heard when letting off the throttle.
I did a compression test and all four cylinders were between 420-440 psi which was encouraging. Then I ran two cans of diesel purge through but there was no change, even while the car was running on the diesel purge.
I was able to isolate the problem to cylinder three by cracking open the fuel line. When I did this the knocking (injector nailing?) went away and when I tightened it the sound returned.
A quick bit of history:
My grand father gave this car to my parents so that my siblings and I would have a car to learn to drive on. It worked great for several years until my younger brother took the car to a "mechanic" to have a fuel leak looked at. Something was replaced (I don't know what) in the fuel system and when my brother got the car back it had the problem that I am now trying to fix. The mechanic told my brother that it just had some air in the fuel lines and that it would fix itself. After a few hundred miles the problem didn't go away and the car was parked and sat for almost two years until my parents gave it to me a couple weeks ago.
Side note:
I love this site, the kits and guides are great. One thing I wish though is that I could have access to an electronic copy of the guides I've purchased. It takes a week for things to ship from WA to IN and I don't want to wait a week for a diagnostic guide to arrive and then wait another week for parts to show up after I've used the guide to determine the problem.
Thanks and sorry for the long post!