I have a 1984 300sd with 274k miles.
The car idle very rough at start. It get smooth around 1k rpm.
When I'm driving on the highway everything seems fine, but when I slow down for an off ramp, the transmission seems to slip/disengage. The tranny also seems to slip when I'm going uphill.

Since both my engine and tranny are giving me issues, I'm thinking this would be a vacuum problem. I didn't change the tranny fluid and filter. I also changed the injectors and adjusted the valves. Both the tranny and engine power problem seemed to get better but definitely no where near perfect.

When I'm idling at a light, I get some smoke coming from the tailpipe.

Any ideas what I should look at next? How does the vacuum affect the idle? I'd like to try and isolated each problem.

Thx.

pete

Seperate problems all around, none seemingly vacuum related. Please keep in mind that you are approaching 300k miles:

The rough idle at start: compression and or glow plug related; possible injector related. Adjust your valves, check you glow system, and lastly, service/replace injectors. The comprossion/injectors would cause smoke at idle, but again, you won't be totally in the clear with anything you do, considering its a passenger diesel with close to 300k, and 25 years old.

If the transmission is slipping while in 1 gear (not between gears), I would imagine it time for a new tranny. Try new fluid and filter. If the transmission is original, congratulations: Your tranny is an old man.

Vaccuum will not affect your idle a diesel, and unless your transmission is slipping BETWEEN gears, it's not likely to be affecting that, either.

What color is your smoke? Different colors mean different things.

__________________
1989 300E 144K

Smoke is sometimes white and sometimes black.
I replaced the injectors. Is there a way to test the injection pump?

I don't have a problem starting it so I'm not sure why it could be related to the glow plug system.

Thx for the feedback.

pete