87 300SDL Sleepy turbo
 

When first getting going in the morning, the turbo does not seem to want to get going. After about 5 miles and then hitting it a little hard it will kick in and then be good. 277K miles-I have had for the last 50K and have never really changed anything associated with the turbo that I know of. Am I missing something?

I remember the guy that sold it to me who seemed very knowledgeable in the way of Merc that he had "fixed" the PCV so that I would never have to deal with it and that just is sitting in the back of my tiny brain that maybe I do need to deal with it.

Will do...
It's still there but I do know the vacuum line is off and plugged.

Going to try to post pic...first time. Seems to work.

Note the blocked off vacuum hose is just to the right of it with the tie wrap.

Excuse me--I have been meaning EGR valve all this time.

I am pretty sure the turbo is "working" as you can hear it spooling if you listen close. I am pretty sure it is some vacuum or valve thing. Any good first places to check?

Hello, If it was me, I would pop that EGR valve off and find out what he fixed. If it is in fact stuck, failed partially open you need to deal with it. They do fail and you should have no obvious symptoms if closed and holding correctly. This might help you before you start. This is from a Mercedes truck manual regarding diesels in their truck line.
Making sure that the valve is in optimal condition is essential to the truck’s function
As a truck owner, it’s important that you keep the EGR valve in good condition. Since it has a direct impact on how the engine works, any problem with the EGR will manifest either as increased fuel consumption or reduced performance. Learning when to have it maintained or replaced is therefore important. Some of the signs that could point to a faulty EGR include:
• An EGR valve that is stuck open: if your truck has a mechanical EGR valve and it happens to be stuck open, it will act as a conduit which causes a vacuum leak in the engine. Some of the manifestations of this include rough idling and even a feeling of hesitation when you try to accelerate. When the problem is severe, you will also notice the truck stalling frequently. When the EGR valve is stuck open, it means that all the exhaust will be rerouted to the combustion chamber, which means that there will be little oxygen which is what is needed for the combustion.
• A valve that is stuck closed: on the opposite end of the spectrum, you can also have a valve that is shut and won’t open. In such cases, there will be an increase in the quantity of nitrous oxide gas in the cylinders, and this will manifest as the engine knocking.
These are the two common problems that afflict the mechanical EGR valves, and thankfully they are easy to fix. All you need to do is identify a competent garage, and have them fix it for you. If you are handy with your tools, you can even maintain and replace the EGR valve with ease. Of course, to do the latter, you will need to buy high quality spare parts from the right sources. Hope that article helps Allan

It starts, idles and runs just fine-hot or cold. I am taking the blinders off and totally rethinking anything about the turbo. I can duplicate the symptoms by removing the vacuum line from what I believe they refer to as the overload protection switchover valve. It will run just fine and even sorta accelerate (barely) but it spools up to 4000 with no issues-it's just a dog. When whatever kicks in it is like a gain of an instant 50HP. When cold, this can take 15-20 mins/miles. Warm start will happen fairly quickly (maybe .25-.5 miles) and once it is engaged, it is fine. When it first started this issues, when cold it would only take a half mile to a mile to wake up but has seemed to have gotten progressively worse.

If I go with the theory that is has something to do with that switchover valve--what does it switch over? Maybe just a thorough replumbing of vacuum lines would help. There just doesn't seem to be anything "wrong" with the car-it just needs whatever it is to wake up sooner than later.

Maybe....?
Mercedes ALDA boost system service

Update-seems fixed
 

Little long but here we go...
I checked out the ALDS thing like in that video link. Was a good idea but didn't really do anything as it wasn't too skanky. Still convinced it had something to do with the ALDS, I changed the valve that controls the vacuum to the ALDS (had no idea how to check that input signal when it was running) and that didn't help.
It was at about this time I knew that my alternator was about dead-no one told me that your ABS light was one of the leading indicators and it had been flickering for over a year. Thankfully had the alternator in hand when all (I and do mean pretty much all) of the idiots lights came on. I had at idle 11.7V at the battery. Changed out the alternator and made all the lights happy and over the next few days the turbo started kicking in sooner and sooner until it was at a level that as soon as the engine is anywhere near up to temp (be it good or bad, I pretty much start and go in the morning), it now works and has been working well ever since.
So it is my theory and belief that whatever signal that kicks in the ALDS has to deal with some voltage differential and if the voltage is really low to begin with, it won't kick in. That's my theory and I am sticking to it.
On a separate note-it was 30 year ago yesterday that it was delivered to it original owner. We celebrated by cruising down the expressway at 90 for a good spell. Its a happy car.