I found a vacuum line disconnected under the hood. It is attached to some kind of a switch that has three vacuum lines and two electrical wires going to it.

It is located on the firewall between the engine compartment and the area where the air filter is housed. It is actually attached to the engine compartment side and I think one of the three lines also goes to the EGR.

What is this thing and what else does it control?

I also found another vac line disconnected that ran along the fender near the air filter housing.

After connecting these two lines, the engine seems to be running smoother and shifts are much smoother. The brakes also feel more luxury-car-like than before. Very nice...

My question is that while the shifts are smoother now, they are still a bit abrupt. The line that was disconnected is showing significant wear on the exterior, probably because it is exposed the the heat of the engine compartment right next to the radiator.

How can I adjust this assuming this line is not leaking any vacuum?

I am going to replace the line tomorrow to see if that helps.

Also, this might explain why my headrests wouldn't work before. I had to hook up the Craftsman copy of a MightyVac to get them down before.

I will have to reconnect them again to see if this was the problem.

Man, I love these cars.

While I did enjoy all four of my W123s, these cars are a serious step up in comfort and luxury.

__________________
1993 W124 300D
-297K on the clock as I type this.

You're "happily" solving a major vacuum leak (That's why the Tranny is behaving now) by "Enabling" all the crap the PO worked so hard to disconnect.

See if you can find time between speed trials to read All of this post:
Wastegate actuator swap for OM602.962?

Rule for "Adjusting" MB Transmissions:
1. First solve ALL the Power problems
(Otherwise you'll be "Adjusting" using the Wrong baseline.)

__________________
'84 300SD sold
124.128

That could be true but I this car has a salvage title because it had a significant front end collision. I have had to reposition the fan shroud because it was being beaten to death by the fan at times.

This line looks like it was knocked off accidentally.

I have seen the inside of the intake and it is very clean. There are only a few droplets of oil in there that I could see.

With this line hooked up, should I expect to see more oil/soot clogging up the works?

__________________
1993 W124 300D
-297K on the clock as I type this.

If that Electro/Vacuum actuator IS the EGR controller,it will (when operating properly) dump EGR contamination into the Intake at low RPMs.

__________________
'84 300SD sold
124.128

Well, I drive anywhere from 900 to 1100 miles a week with work and 95% of that is highway miles.

Under these conditions should I see any problems?

__________________
1993 W124 300D
-297K on the clock as I type this.

Remember you're talking to a "Clean Intake Freak"...
Disabling and Removing the EGR (AND Gutting the "Flapper")
IS NOT sufficiently clean for me...
One of these is in the "Breather" line that runs from the Valve cover to the
Intake:http://www.aircraftspruce.com/catalog/eppages/hboilbreather.php

Attached Thumbnails

 

__________________
'84 300SD sold
124.128

Well, since there was no black goo in my intake before I hooked this thing back up and since I realize that it is only for emissions compliance, I unhooked it again and plugged it with a golf tee.

Now, I have even better shifting(the vac line is showing some serious wear and tear) and the brakes work as intended.

I will be replacing the vac line tomorrow with fresh line and re-inserting the golf tee.

__________________
1993 W124 300D
-297K on the clock as I type this.

Happy Motoring!

[Blatant Plug for "Clean Engine Compartments"]
Wastegate actuator swap for OM602.962?

__________________
'84 300SD sold
124.128

Copy my traffic? Is that in reference to my speed test?

OK, now I have another question.

Have I altered the function of my turbo at all by bypassing this EGR actuator/controller?

I am completely unfamiliar with how a turbo works except that it uses the exhaust to turn a compressor that in turn compresses the intake air supply.

What is a wastegate and how is it actuated?

By bypassing this line have I compromised anything other than EGR function?

__________________
1993 W124 300D
-297K on the clock as I type this.

Your Turbocharger has a "Pressure Air Dump" valve nicknamed a "Wastegate"
[It "Dumps" the Exhaust (Powering the Compressor Wheel ,on the other side
of the Turbo Shaft) back into the Exhaust System,thereby DePowering the
Turbocharger.]

The "Wastegate" on your Mercedes 124.128 Chassis (602.962 engine) is
operated by an Electro/Vacuum Signal from the EDS (Electronic Diesel System)
[AKA the Computer]

Disclaimer:
I'm crazy if I tell you you haven't altered your Turbocharger Wastegate...
Because ALL the Damned Electro/Vacuum Actuators that control the
EGR/Emissions system are ALL in that area you described.
AND I REALLY don't know which one you've been playing with.

(I kinda Glommed onto the idea that the Actuator you had aholt of was for
the EGR...because it had [from your description] a Vacuum line connected to the EGR...BUT Who
Knows?)

The whole point of the Pressure Operated Wastegate Saga I've been steering
you towards...IS...It Simplifies the wastegate system AND removes it
from the Computer's control.

I.E.

Boost goes up to 14 PSI ...Wastegate opens...Period.

__________________
'84 300SD sold
124.128

Not sure if I'm supposed to start a new thread or post here. Correct me if wrong please...
I too am experiencing the vacuum nightmare with my 1993 300D. I purchased her 6 months ago. I found a ball bearing blocking the EGR system and the EGR valve stuck shut. Since opening the line, replacing some vacuum lines, and freeing up the EGR, I have improved performance/fuel mileage, BUT, Still the following:
-23 seconds for 0-60
-hard (delayed) shift from 2nd to 3rd (unless I let off accelerator)
-sluggish/pathetic uphills
-no cruise control
-poor acceleration
Any advise would be greatly appreciated. I tried to get some codes using a homemade code reader I assembled but it did no blink. Was basically a flashlight with a button when hooked up
M goal is to get the vehicle running correctly in stock set-up so I have a solid baseline from which to upgrade. Thanks!

Should be a new thread.