Hello all-

I have searched to find the closest thread that relates, which seems to be the vacuum diagrams thread. I asked there, but in case not many people see that, I'll ask here too. If anyone knows thread(s) that already discuss this, please link me to it(them) as I am a fairly good searcher but came up pretty empty.



I have two different vehicles to ask about.

One is a 1982 300D turbo, not mine but a friend's. I am asking this for him. The engine was replaced by someone who was not qualified, and much of the vacuum system is not hooked up properly. They have gotten it to where the brake system functions, so some of the vacuum lines run correctly. But the engine still does not shut off, so obviously other parts of the vacuum system are not hooked up correctly.

The question is: Will it (could it) hurt the transmission to drive the car with not all of the vacuum lines hooked up correctly? He wants to drive it to my place, about 60 miles, to have me work on another part of the car. But is wondering if the vacuum system not working will cause damage to the transmission if he drives it.






The other car is an 87 300SDL. This one is mine. Several times when accelerating, at the point where it would shift from 2nd to 3rd, the rpm would jump up between gears as if the transmission were slipping and then catch the gear and resume normally. It didn't happen often, and so by the time I would stop I would forgot to check the fluid level. It probably happened a total of 5 or 6 times spread over a two-week period.

The other day I was accelerating rapidly (I was pissed off about something and driving like I shouldn't have been) and about 3500 rpm or so the power dropped. I first thought fuel starvation, possibly a plugged fuel filter, and eased off the accelerator. But after a few minutes of driving, I could tell that it was running smoothly and consistently, just with not much power. On my next stop I checked the transmission fluid, and added about 7/8 of a quart. I had recently read that there is a computer in this car that looks at things including the transmission to decide what to do. Perhaps it detected low fluid and went into some sort of a "limp" mode.

After topping off the fluid, the power did not come back. I unhooked the battery overnight in an attempt to get the computer to reset itself (having no real idea how this thing works!). But it didn't help.

I have now been driving it for several days, and it runs real smooth and seems pretty consistent, but just doesn't have any power. And it shifts a little harder now, but my guess is that's because I'm standing on the accelerator more. The shift I get now at about 3000 rpm is comparable to the shift I used to get over 3500 when standing on it, which makes sense if it uses throttle positioning as one factor to determine shift.

I do not know if the transmission situation is related to the loss of power, or just coincidental. I have looked and cannot see any vacuum lines loose (but have not looked under the car).

My questions here is: Could this be vacuum related? Any insight into what could cause this symptom?

Thanks for any feedback anyone will give.

Jeff

No, it will not hurt the transmission.





No, it is not vacuum related.

The problem is either fuel filters........or the lack of boost signal to the ALDA.

Change the secondary filter and thoroughly clean the boost pressure line from the manifold to the overboost control valve on the firewall........and additionally the line from the overboost control valve to the ALDA on the top of the injection pump.

Thank you Brian. I am sure it is not fuel filters, but was totally unaware of the boost pressure lines from the manifold to the control valve and from the control valve to the ALDA.

Which sounds like would cause EXACTLY the symptom I have. Will check those tomorrow.

The place I read recently about the transmission possibly an issue was here:
http://www.frybrid.com/forum/showthread.php?t=2236&highlight=strange+animal

The person who posted that original question ended up posting the solution as being the same thing you said here, Brian, if I'm not mistaken.

Again, I will look at that tomorrow.



The administrator of that forum suggested among the things mentioned a dirty trans filter. As much as I know about some things in cars, I am not informed on this one. Does this car have a trans filter?

Jeff

It was lack of boost signal to the ALDA.

And not from EGR tar, either. I had run a coolant hose near where it is, and the line from the manifold to the valve had come off there where I didn't see it even when I was looking.

I assume that whaen I was driving too violently that day, the engine must have wobbled enough that that coolant hose bumped it. I re-routed, re-connected, and everything is fine.

And I'd not have found it for who knows how long if Brian hadn't told me exactly where to look. I had checked for loose lines and found none, and as I say this was hidden under a hose where I didn't see it.

So thanks to Brian for telling me what it was, so I'd know exactly what to look for!

Jeff

Good job.

We all love it when the advice works.

Help is what we do here.