Where is the vacuum modulator?
 

I have a 1990 190EE 2.6 and just today, my shifting has been horrible. It seems like the shift goes immediately from 1st to 2nd to 3rd. And even if I put the gas pedal all the way to the floor it slowly climbs up from 20 mph to the normal speed limit which is 40 mph. I read several posts on here and they all seem to point towards a vacuum modulator, but I dont know where it is or what it looks like. If you have pics, that would be great too. Thanks guys.

or maybe it isnt a vacuum modulator, but something else. Not sure, please advise

Answer
 

Got your PM, here is the answer.
I would need your VIN# for correct part.

Transmission:
http://www.peachparts.com/shopforum/diy-links-parts-category/142395-transmission.html



Have a great day.

As per your VIN# the part is MB# 126 270 25 79.

hey, thanks, im still trying to figure out that pic though. im guessing the best way to approach this would be from underneath with the car on jack stands. am i in the right area by checking the modulator or would there be another cause for my shifting through all 4 gears before the car even reaches 10-15 mph?

Answer
 

Possible bad "kick down" switch.
MB# 002 545 22 14
http://catalog.mercedesshop.com/item.wws?sku=W0133-1626222


Under the accelerator pedal...

Did you check the Bowden cable? It might have come loose, and that is what affects shift vs. throttle position.

Steve

whunter- I found out where the kick down switch is under the gas pedal. I was able to disconnect it and look at it. It has a small black cap on top of it and I am able to depress it, but I have to put moderate pressure on it....like stapling 10-12 sheets of paper (that kind of pressure) is that normal? I also had it disconnected and decided to drive around in my parking lot and noticed that I still would cycle through all 4 gears at 17-20 rpm and still be under 20 mph. So no change with it off either.

sbourg- How do I check the bowden cable? I'm assuming the cable with the white nut that you are able to twist that sits under the air filter. I did remove the air filter cabin and there is another cable that if the car is on and you move the metal piece attached to it, it revs the engine. (sorry, I'm not too familiar with the names, just certain parts and what they do). Anyways, I noticed that when I moved the piece it was slightly sticky, not much though. So I srayed the movable parts (hinges and cables) with WD-40, they move more freely now, but I took the car for another test drive around the lot and nothing. I did not check to see if the Bowden cable came loose because I don't know where the other end terminates at. It disappears behind the firewall somewhere.

190E shifting through all 4 gears at 18-20 rpm and under 20 mph.
 

My transmission started shifting through all 4 gears when I accelerate from a dead stop within 5-6 seconds of acceleration and the rpm stops at 20 and I'm still going 10 mph and no matter how hard i step on the gas the car slowly crawls up to speed.
Well as I was looking under the hood, I found this vacuum line (see pics).
The rubber elbow was connected to the small metal part circled in the picture, its hard to see but it is right next to the valve body.
Anyways, it was the only vacuum line that I saw that may possible be related to the transmission so I disconnected the rubber elbow part and slowly began to pull the line to trace it to the source and lo and behold it was disconnected from wherever the other end goes.
I traced it down somewhere past the oil filter, or somewhere in that area. Bad news is I have no idea if this is the source of the shifting problem or not.
http://i90.photobucket.com/albums/k2...2/IMG00063.jpg
http://i90.photobucket.com/albums/k2...2/IMG00060.jpg
http://i90.photobucket.com/albums/k2...2/IMG00062.jpg

Not really understanding what your trying to explain i will say this about the symptom

UPSHIFT too soon all gears --

the Boden cable ( downshift cable USA ) controls the when a trans shifts in a MB and the modulator determins how firm the trans shifts gears

My guess the boden cable is broken or has come un hooked < the first thing i would check than post again - jz

Yes, upshifting too soon, I was able to track down bowden cable and it is fine. But what about this vacuum line I hav e. Where does it go?

Answer
 

combine post #2 and #3 with this attached picture to restore vacuum to the transmission.



Note:
Do not make multiple threads on the same issue.
Moderators can change your thread title on request.

Sorry about the multiple posts. So the one end goes on top where it is circled and the other end goes on the vacuum modulator? Do I have to disassemble anything to get to the modulator? I just went and bought 2 ramps to elevate my carb so I now have a little access underneath....

Answer
 

NO.
It is all external = connect the hose on each end, and you are done. :)

Sorry for beating a dead horse, whunter, but what you are telling me to do is to reconnect that rubber elbow/vacuum line to the metal end fnext to the valve body ( as in the pictures I took) and then just plug up the other end of the vacuum line?

Answer
 

Post #2 shows a picture of where the other end of the vacuum hose must connect...

One end connects to the intake manifold.
The other end connects to the VACUUM MODULATOR.

perfect! i got it. one more question and everything should be all set: how do I access the vacuum modulator? is it easily accessible? do I look under the hood or under the car? I see the picture, but unfortunately i dont understand how i would get to the modulator to reconnect the hose.

Answer
 

Under the car.
It is mounted on the driver side of the transmission.

ok, i was under there not too long ago with a flashlight, but couldnt identify it? is it before the transmission filter box? or do i need to take anything out of the way? just did a search on here and google for any real photo of it, but cant get one

Answer
 

picture attached.

Oh yes! I did see something red from under the car. it was dark outside, but I'm sure that was it. It was on the side of the transmission. I will try to take care of it tomorrow morning. Will keep the thread updated. Hey thanks for your help and patience whunter!

Ok, so I reconnected the vacuum line back to the modulator, but I am still having the same problem. Any new suggestions?

Transmission:
http://www.peachparts.com/shopforum/showthread.php?t=142395

Thanks again, whunter. I will go back out and try to maybe adjust the modulator by turning it (I think I read that in one of the links that you posted).

Ok, reporting back. still having the issue. How hard is it to remove the vacuum modulator? As I was reconnecting the vac line it was really difficult to get to it...I actually had to sort of threat it through to the rubber connector because I couldn't physically access it with my hands. Could it be something other than the transmission that is causing tthis problem?

I'll add my Vacuum Modulator experience. I purchased my '93 190E 2.3 new and it always shifted hard from first to second gear. I replaced the VM when the VM started leaking transmission fluid through the vacuum line. The transmission never shifted better and so smooth... it still does.
To replace the VM, I had to disconnect the exhaust system hangers so I could lower the transmission enough to gain access to the VM bolts.
Also, this would be a good time to replace the shifter bushings while the transmission is lowered.

http://i179.photobucket.com/albums/w...ModulatorA.jpg

Lowering the transmission??? Not that seems a bit out of my league unfortunately. Can't I change the modulator without lowering the transmission? What if it isn't the modulator? Oh and by the way, I had my shift bushings changed last year, that I do remember. ...Working on people is a lot easier, I wish I could just do an engine biopsy and find out what the problem is. :)

I tried to remove and install the Vacuum Modulator by just lowering the transmission with the cross support removed and could not do it.
Fellow forum member MTI posted that I had to remove the exhaust/cat. hangers in order to lower the transmission enough to gain access to the VM bolts.
If this old retiree can do it, anyone can.;)

Hey quick question guys: I have not had a chance to get a new vac mod yet, is there any harm in driving the car while the modualtor is out of commission?

Not to hijack (which is what I'm doing), but how can I get my gasser to stop lurching into gear from P/N (both forward or reverse)? There seems to be a bit of extra play in the pedal to get it moving from a dead stop, but after that it seems to run/shift just fine.

My issue with my modulator has been resolved. It resolved itself and I didn't have to replace it after all.

dhjenkins- you might try the little knob under the gas pedal...that controls the idle speed....well at least thats what the issue was on my 190E. Had it turned too much which caused me to have a high idle and everytime I changed from P to D or R it would lurch forward a bit. Hope that helps.

Was not the kickdown switch I was referring to for dhjenkins.....I don't know the name of the part as I am a noob, but there is a white plastic screw under the gas pedal that connects to the throttle cable(?) and if u turn it clockwise it will increase your idle speed. Same as the cable under the airfilter cabin. If you turn it.....not sure which way, it increases the idle speed or decreases it.

No, my idle is at 650, which is right where it should be...

The modulator controls shift "harshness", correct? I know it's connected at the modulator, but I have yet to actually check the operation or that the hose doesn't have a hole in it...

That is not used for idle adjustments. Be careful to not adjust it so that the Micro Switch doesn't open and close correctly or you will affect the idle.

Slk230- yeah I had the idle really high, but I was able to fix it to the proper idle speed.

Dhjenkins- yes, the modulator does affect the harshness and softness (flaring) of the shifting. There is an adjustment rod that you need to turn to get it somewhere in between harsh and soft. Go to the resource tab at the top and look up vacuum modulator DIY articles. Or you can back track this thread, as whunter has posted some very helpful links. Hope this helps you. Please keep us updated on your findings.