Aloha all

I am baffled and hoping I can get some guidance.

I have an 84 300 td wagon and when I went to drive it today the engine wouldn't idle but stayed reved up to maybe 2000/2500 rpms ? (tach is broken) when I tried to shift it into gear to get it home, it would just stall. At home I tried to adjust the idle with the idle adjustment screw and can't seem to make sense of how it responds. when I turn it in- nothing and then sometimes it will idle down and stall and sometimes will continue to just run at a high rev.

I just replaced the injector nozzles and reset the valves. It is not a great engine and compression was kind of low with one cylinder down to 220 ( rest between 300 - 350 ) and some blowby When my wife drove it yesterday she said it ran 'fine' and then all of this started today?

What am I missing or doing wrong?

I am also still looking for someone experienced to barter a 617 tune up tutorial for some time in our B&B on Molokai in Hawaii. There is no Mercedes shop or mechanic here. I am self taught. I am an experiential learner and it is a frustratingly slow learning curve...