617 tune for smooth running as it was designed
 

The 85SD is slow the 84SD has a little shake at idle. I'm contemplating strategy for when the weather breaks.

So:
Change fuel filters (done)
Make sure strainer is clean (done)
Adjust valves (both cars were done in the fall)
Check timing chain stretch (not done lately)
Check timing (not done)
Clean, pop injectors, perhaps new nozzles
Adjust Rack Damper, replace as needed
Check/Adjust boost

What else?

Check for fuel leaks at IP. Consider replacing the copper crush washers in the delivery valves.

If your injectors have more than 100k miles of service, I'd say they are probably the most likely culprit.

There can be a huge difference and many things can affect the idle quality. Look at these two cars; both 1983 300SDs:

https://www.youtube.com/watch?v=tHFhjbAg8MQ&list=UUX3YyyjeCyrrjETZIhZm95Q

Both have relatively new motor mounts. The one that shakes has a trans mount also. 178K on the (working now & when I bought it) odometer. I intend to pull injectors & send them off.

These cars deserve to be brought back to specs. I'll do front & rear bushings & whatever else is needed for the suspension to become new again.

Was wondering what Is missing from the above list.

Once you get them running smoothly, you won't understand how you dealt with them shaking before. It really helps the car come together and feel like a real luxury vehicle.

If the above fixes your rough idle, great. I have found that replacing the delivery valves in the IP was necessary to make the biggest difference in the car with the shaky idle. Reaming the GP holes can help a little, too but mostly with startup.

You might want to add a diesel purge to the list. Checking length of relief spring in the IP?

If you found the valves to need adjustment, it really helps considerably to do another valve adjustment back-to-back about 500 miles down the road. I found this helped my idle shake more than anything else.

Getting my injectors rebuilt with new nozzles and balanced properly be a certified Bosch service center helped a lot. After I had that done then the rack dampner bolt actually did something! I can turn it out and the engine will rock back and forth, screw it in and at a certain point it just stops. Could not get it to stop shaking before the injectors were done though.

It still vibrates, but it was rocking before. It would rock the car!

Being a bottom feeder, I never had the opportunity to own an 82-85 300D when new. Can anyone who did let us know how the engines felt right off the dealer's lot. Mine barely shake at idle and are fairly quiet in the cabin with the windows closed. From 100 ft away you might not hear the engine idling. However, the engines sound a bit loud on the highway, especially above 60 mph. It seems like I need a higher gear, since even my 85 CA (w/ 86+ tranny) spins ~3000 rpm at 60 mph. If like that new, it is hard to believe these were considered luxury cars in 1985. I am guessing there are some openings to the engine compartment that allow the noise, since even a tiny opening can transmit a lot of sound.

My 300SD is really insultated. It has a 3.07 gear ratio so it sits at about 2600 rpm on the highway. Doesn't seem too loud. I'm even missing the grommer where the oil pressure line comes in through the firewall. It's going to be louder than a v8 at 1500 rpm.

Add:

Check idle speed and adjust if necessary.

Check your fuel pressure. If lower than it should be it does make the idle both noisier and rougher.