BenzWorld Junior Member
Date registered: Mar 2019
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'88 190e 2.3 - Vibration in Drive - Idle microswitch and ICV seem to be doing nothing
First post, first time owning a Mercedes!
The one main problem it has is that it is rough and vibrates ONLY when it's STOPPED and in DRIVE. In Park or Neutral, it's great - smooth 1000rpm idle. When you take your foot off the brake and give it gas, it operates like a totally normal car.
I have done some research and found that maybe this is related to the ICV or the idle switch (is that even what it's called?) - the switch that gets hit when the throttle linkage touches it.
When I manually open and close the switch, there are no changes to anything, so I tested it by putting a meter on it, and it seems fine - the switch makes and breaks the connection when it's pressed or released.
I can't detect any power getting to the plug that goes onto the switch when I stick a lead into either side and ground the other. I also can't detect any power getting to the plug for the ICV using the same procedure.
Is the idle switch related to the ICV? I seem to remember reading somewhere that the switch runs the ICV.
Is the ICV supposed to be normally open or closed? When I take the top hose off, I can see that it's closed, but with a small gap that I read is normal.
Just now, I went out and pulled the connection from the ICV, connected the leads from a 12V power supply to the pins, and turned it on and off, which caused the engine to rev really high without pulling the throttle at all. I'm guessing what that did was open the valve.
Last week I was jacking around with the throttle cable, linkages, and opened and closed the ICV without the car being on, and for a short time, the car was really peppy and ran totally smooth when stopped and in drive, but then went back to what it normally does. No idea what I could have possibly done to make it run normally temporarily (literally a couple seconds).
Anyway, I'm out of ideas for this thing, so I've come here. Hope someone can help.
Backstory: Me and a buddy got a 190e to play with for $600 and there was barely anything wrong with it - runs, drives, stops, passed safety inspection. We're in Texas so no emissions since car is >25 yrs old. We have done some regular maintenance type work to it. So far we've done an oil change, ATF change, spark plugs, coolant flush/fill, ignition coil and ties. We can drive it around town no problem - even on the highway it's fine, but this vibration/rough running in drive is getting on our nerves especially since we've changed so much on it so far.