i just bought a 83 300td. it was starting in 1st at every stop and the idle was set high. i thought the high idle was tricking the the transmission into downshifting. i wanted to correct it and have the car start in 2nd. because it would hard shift from 1st to 2nd. i drove it about 10 minutes to warm up the engine and then adjusted the idle down about where it is on my 77 300d. then i reved the engine and let off the throttle. but when the rpms came back down it would stall. i adjusted it up until it wouldn't stall. as the rpms came down from high nearing idle it would slow down for a 1/2 second (almost as if it wanted to stall) and then up to idle.
then i drove it around the block. the adjustments that i made intensified the transmission problems. not only did it continue to start in 1st but it would stay in 1st longer(until 25mph) then shift harder into 2nd and then almost immediately into 3rd. this at normal acceleration. when i floored it, it would stay in gear way to long. it didnt shift into 3rd until 40mph.
i then looked in the haynes manual and all it said is not to adjust the idle on a 80 and up cars.
how can i have a normal idle and start in 2nd.

 

If you want to start in 2nd every time everytime you stop move the Shift Lever into 2nd Gear. When you get moving move the Shift leve to Drive.

I would put your idle speed back to where it is supposed to be; the speed should be on the emission sticker up by the Radiator .

Also before you start adjusting things you should read up on it first.

A I copied: TRANSMISSION STUFF Bodwen cable
Vacuum controls only the quality of shift transition (my thought meaning the harshness of the shift). The bowden cable on top of the valve cover controls shift timing (when it shifts).
Another commet I copied:
Bodwen Cable
messing with the bowden cable to reduce the shift point a bit. Is a CC turn make the shift at higher rpms
Yes, but make very small adjustments. Try changing it 1/4 turn.


If I was you before you mess with the Bodwen Cable I woud make sure the Vacuum Valve adjustment and the Transmission Modulator were adjusted first. Also take a look at the Transmission Modulator and see if the cap covering it is cracked or gone; if so replace the Cap.

 

Hi,
I have the same problem with my 300 TD shift very rough, where is the trans modulator located?
benzyman

 

where is the bodwen cable at. the linkage is different then on my 77 300D. and does what this guy is talking about seem like probable causes of what may be the problem with mine. http://www.dieselbenz.info/tranny.htm
is my problem a vacuum issue?
how do you use vacuum to adjust how it shifts?

 

You have to read through several pages to get to it but this article explains the vacuum issue.
http://www.continentalimports.com/ser_ic20242.html

 

that was a good link. i read through it and bought a vacuum gage and started checking the system. and there are a few issues.
there is 21"Hg off the booster hose. it has the potential for 12"Hg making it to the control valve. but when the hose to the control valve is connected and i test it above the control valve it only pulls 7-8 inches.
it also doesn't vary with the throttle. it pulls the same amount until full throttle and then it drops to 0.
when i adjusted the nut under the plastic cap i was only able to produce 2 results. 1 it i adjusted it far enough in one direction i it would lower the vacuum to nothing, and 2 if i adjusted it far enough in the other direction it would raise the idle rpm. (and its my opinion that its idling too high in the first place)

my testing makes me think that the valve is not functioning properly. should i try to repair or replace the control valve?