I got my ass kicked trying to get to the bottom of an intermittant performance problem, went through all the usuals, so I took it to a mechanic in the area that I only use when I don't want to do the work, which isn't very often. He tried to adjust the ALDA, and the setscrew and locknut both fell off. Luckily I had two virgin spares in the trunk, with shims.

Shazam! Car's got more power than I ever knew possible, with no more smoke than before. So- if you've tried it all, and you think your ALDA works because the screw ain't broke off, well it just might be leaky anyways. It pays to test. I am now convinced that I have been living with a leaky ALDA the entire 4 years that I've owned the car. The car hauls ass now.

__________________
'02 BMW 325i
'85 300D 450k
'93 190E 2.6 170k(killed by tree)
'08 Ducati Hypermotard 1100S 6k
'06 Ducati S2R800 14k(sold)

If the o-rings on the shaft are shot, the pressure from the manifold will leak past the seals and the ALDA won't see the boost.........even if you have it from the overboost valve.

This is a common and generally overlooked problem because it's very difficult to diagnose on the vehicle.

A boost gauge, when connected, will read low boost.........causing the owner to seek out problems with the turbo.

In reality, the turbo will make the boost if the ALDA wasn't leaking pressure and provided the fuel.

Testing the ALDA for pressure should be part of the procedure whenever "no power" is the symptom. It doesn't need to hold pressure completely, but shouldn't leak down faster than about three seconds or so. Any faster leak will cause a reduction in boost pressure to the ALDA.

Glad you found the issue.

Others should take note of this thread.

Thank you for the post. I'm putting it on my list of things to check on my car.

Chris

__________________
1987 300TD 309, xxx 2.8.2014 10,000 mile OCI


Be careful of the toes you step on today, as they may be connected to the ass you have to kiss tomorrow. anonymous

“Be who you are and say what you feel, because those who mind don’t matter, and those who matter won’t mind.” Dr. Seuss

Yes. That reminds me, I must now check max boost. If that reading was taken at the old ALDA connection, which it was, and it read about 11psi, then it stands to reason it may be conservative. I tweaked the wastegate last year, so I want to make sure it's not overboosting.
It is definitely a different car now.

__________________
'02 BMW 325i
'85 300D 450k
'93 190E 2.6 170k(killed by tree)
'08 Ducati Hypermotard 1100S 6k
'06 Ducati S2R800 14k(sold)

That sounds like a different scenario rather than leaking seals. 11 psi is just about enough to push the ALDA to it's limit. Therefore, it's clear that the ALDA was not functioning properly, despite proper seals.

You may find that the boost pressure will remain at 11 psi with the new ALDA, thereby confirming that the ALDA seals were not the issue.

This would confirm that the replacement ALDA has a significantly advanced fuel curve as compared to the original unit.

not to jack the thread, but, i have a friend who owns a 91' or 92' 300D, it is also sluggish, they have taken it to the mechanics a number of times and he cant figure out what is wrong with it.
the ALDA has never been touched, do u think that i i do that for them that it might solve the problem, and is there anything i should know about taking the intake manifold off?
-thanks

__________________
82' 300SD

Those have computer controlled wastegates and will cut boost if all engine parameters are not within spec. They are definitely a PITA to diagnose and you'll need a competant mechanic to troubleshoot the codes and replace the faulty sensors. Find a different mechanic.

Here's an interesting read on the same vehicle:

EDS Codes on 1992 300D 2,5 Turbo

There are several members with those vehicles who have suffered the same fate. All devices that have input to the computer must be functional and within specs, or the computer kills the boost.

Another problem that causes performance problems is the lack of the throttle linkage touching the full throttle stop on the IP at WOT.

__________________
'81 MB 300SD, '82 MB 300D Turbo (sold/RIP), '04 Lincoln Town Car Ultimate

Sooner or later every car falls apart, ours does it later!
-German Narrator in a MB Promotion Film about the then brand new W123.

I think I might try and take it apart. Those four screws are a bear to break I know. The kind of screws that require the exact Phillips head # to free otherwise you'll strip 'em. It might be that the aneroid capsules are broken from a previous owner, or that the setscrew was broken down inside, allowing the threads to function normally on the upper piece of the screw, and letting me think I was making an adjustment that wasn't making any difference THE WHOLE TIME. This car was designed by Willy Wonka for sure. It is a CONTRAPTION. I love it.

__________________
'02 BMW 325i
'85 300D 450k
'93 190E 2.6 170k(killed by tree)
'08 Ducati Hypermotard 1100S 6k
'06 Ducati S2R800 14k(sold)

With a homebrew code reader and an in-depth knowledge of the workings of the EDS system, it really isn't all that hard to pin down the malfunctioning part. The transducer that controls the wastegate actuator can go bad, which will result in no boost even if the computer calls for it. Do some searching, recently there have been a number of people (including myself) trying to troubleshoot these 2.5's. But when everything is in order, they sure are fantastic cars.

__________________
Dale

http://i52.photobucket.com/albums/g1...MG_2277sig.jpg

1990 300D 2.5 Turbo -155k
2000 E430 - 103k
2014 Jeep Grand Cherokee Ecodiesel 4x4 - 11k
2014 VW Passat TDI SE - 7k Bro's Diesel
2006 E320 CDI - 128k Pop's Benz

Pre-glow - A moment of silence in honor of Rudolph Diesel