WELCOME VINCENT ! .

You have a series glow plug setup, this means that when one dies (goes open circuit) ALL of them stop working .

To properly test you'll need to search up an older post, there are plenty .

Many here replace those early typ glow plugs with parallel ones and have far less issues cold starting .

It's normal for your engine to run roughly on cold start, that's why there's a fast idle knob on the dash board .

DO NOT rev. the crap out of your cold engine ! .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better