Hi All,

I have read as many threads as I could find on this performed all the recommended adjustments: throttle linkage, Vacuum control valve (VCV).
I verified the vacuum layout with the correct diagram. I have the MBZ W140 CD-ROM.

The car is 1992 300SD new motor 603.971 and a rebuilt transmission 722.34 with approx 500 kilometers on rebuild.Mobil 1 ATF.

The car when cold won't shift from 2-3 for the first 5 minutes or so, they start off in 2. To get it to shift, I have to let off of the throttle, sometimes it shifts and sometimes it does not.
Once warmed up 10 minutes or so it shifts much better but not perfect.
If I removed the vacuum line it made no difference in the cold shifting.

I performed the following vacuum tests.
To the VCV at idle (engine running) the maximum vacuum was 10 inches.
output of VCV with engine at idle 10 inches.
Vacuum at the vacuum pump , small port, direct to gauge was 22 inches.

Using a mighty vac with engine off:
Connected to VCV input, vacuum gauge on the ouptut- VCV was able to pump up to 15 inches and the VCV held vacuum- VCV at idle position.
Output of VCV with 15 inches on input- approx. 10 inches @ idle, and 0 at WOT.
15 inches to transmission modulator via tube connected at VCV-held 15 inches for approx. 20-30 seconds, then bled off slowly

According to the manual the VCV it suppose to supply approx. 0.4 BAR at idle and 0 at WOT.
1 bar = atmospheric pressure.
This should be 11.812 inches of mercury. The input to the VCV is only 10 inches.
Right now it is letting the same out that is going in.

As you know the small port on the vacuum pump supplies many items- the EGR, turbo boost, and transmission. There is also one lead that goes to know where, it is open to atmosphere. I tried covering the pipe and it causes the engine to shutdown. The diagram states that it goes to the interior fresh air-looses bit in the translation I think. The climate control system has it's own vacuum source.

A couple of ideas:
1. I still need to check the transmission modulator directly.

Any ideas would be appreciated.

thanks in advance
Steve

bump

Q1 - When was the last fluid & filter service?

Consider isolating any non-essential vacuum user components using golf tees so you can determine IF this might be a combination of temperature AND vacuum leak.
Regards,