Hey...fixed it myself.
I took a shot in the dark, cooked my arm fairly thoroughly and traced one of the mystery lines out to what has to be EGR under the fuel distributor. I then found the line running down to the trans, which was hooked to manifold vac, disconnected it and reconnected it to the open side of the mystery line. I then reconnected everything else back up using the best guess/most likely location method.
Pretty amazing transformation. It raised my vac to the ACC enough to help, but not completely fix, my climate control, but now I have no more harsh shifts, it actually firmed up the 3-4 shift a bit, moved the shift points to about optimal, fixed the kickdown and must have gotten the EGR working again. It's like a whole new vehicle. No more slug trail behind it...it's actually pretty peppy now. The idle also settled to about 700 with the air on or off. It seems to start much quicker, and the switchover from a/c on to off and vice versa can no longer even be felt. I think if I can find a good check valve to put in the ACC vac line, that will fix the rest of my problems. If not, I'll have to rig up some kind of vac pump similar to the one that runs the lock system. It's a surprising smooth car now.
Originally posted by cknoch
I have a 1988 190E that I have been trying to straighten the vacuum system on.The previous owner seemed to enjoy making it tougher than it already was.. I have the typical problem of cool air in the center vent and hot coming out the sides...I have managed to make the system work by removing the yellow check valve on the firewall in front of the driver and replacing it with a tee fitting. I tried a replacement but that didn't help. Now the system works great except when I step on the gas, I hear the air doors open when the vac drops and it allows hot air through the side vents until you reach cruise speed and the vac comes back up. I have completely removed the dash and checked the entire system for leaks, with none found. The button panel works and the vac valve under the pass side A/C vent seems to function jst fine. Basically, I just don't seem to have enough vac to run the system correctly. I also have another mystery that is probably related, and if you can give me a bit of info I'm guessing that I can fix the above problem along with some harsh shifts from the auto trans in lower gears.
I have a mystery vac line that originates at the more rearward of the two temp sensors at the water neck, just at the front of the valve cover (2.3L). It has been run along with most of th engine wiring over to the drivers front fender, where it enters what seems to be a check valve. That valv has to othe nipples...one on the botton that has a 2 inch piece of hose that is not plugged into anything and another that goes into a slightly larger line that reroutes back along the wiring toward the engine and then disapperas under tha manifolds and into the trans tunnel, the best I can trace it out. This seems to be a ported vacuum source since there is vacuum on the open piece of hose after the engine warms up that only appears with increased engine RPM. If I had to guess, I'd guess it to be EGR and trans kickdown, but that's a pure guess. Can anyone clue me into what this is? I feel like if I can get it back on right, most of my ACC and trans problems will be solved. By the way, I tried replacing the taillight bulbs with OSRAMs and that DID fix my cruise control. Nutty.