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1995 Mercedes S350D drives weaker and shakes when warm

Over the winter the car starts right up and you can actually see the STEAM from exhaust, no shake. when the weather gets warmer it drives weaker, shakes more with black smokes at times especially at low RPM ~600-700. I put the car on neutral at stop so or I press on the gas paddle a bit to get less shaking. On cylinder 1 there is always a small pool of diesel at the injector nozzle. I have also turn the idle adjustment pin 2 or 3 times so the car won’t idle at 3-400rpm and shuts off when there is strain on the car.

The forum won’t let me post longer message so i will add on these. It is about 180k miles. It is an I6 diesel engine, 3.5L.
Even in the winter after maybe 20-30min driving the car gets a bit weaker and shakes a bit more(shorter time frame if I have less diesel in the tank). In the winter it idles about 8-900rpm. The small pool of diesel does not overflow but I have always noticed it since I got it 2 years ago. I have also tried to dial up the idle adjust pin 2 or 3 times when I first got the car so the car won’t idle at 3-400rpm and shuts off when there is strain on the car such as turning wheel really hard. Can anyone help me to pin point the problem? What should I do first?

Benz diesels are really not a do-it-yourself project…The FIRST step, at this point (180K miles) would be a compression test…

“The small pool of diesel does not overflow but I have always noticed it since I got it 2 years ago.”

I suspect this is something that will cost a few bucks to cure and is a major part of your problem…Again, you should consult with a good diesel mechanic who can actually see the problem…Nobody here can do that…

My vote is also for running a compression test and making sure there’s not an issue with the engine internals.

Only simple thing I can think of is a fuel filter - how old is it? And you’ll also want to check the valve adjustment (if they’re not hydraulic lifters). Also, is the timing chain in good shape?

If your Benz diesel has rubber injector fuel return hoses, these can eventually leak where they push on connectors at each injector. New hoses may be in order. You may want to get your injectors’ spray pattern checked. At your mileage, the injectors may be worn. If they are, ask if you can have the injector spray nozzles replaced for less money than replacing the injectors.

Well why dont you just upgrade your mercedes. sure it is compression though.