'88 190e 2.3 - Vibration in Drive - Idle microswitch and ICV seem to be doing nothing - Mercedes-Benz Forum
 
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post #1 of 5 (permalink) Old 03-20-2019, 09:27 AM Thread Starter
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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.
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post #2 of 5 (permalink) Old 03-20-2019, 10:01 AM
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Check the engine mounts....causes engine vibrations at idle. As they age they collapse.

https://www.benzworld.org/forums/w20...unts-were.html

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post #3 of 5 (permalink) Old 03-20-2019, 11:07 AM
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Welcome to the forum.

As a new member, it is always a huge help if you state the mileage on the car.
A 90K mile car issues are generally different than a car that has 250K miles. So it gives everyone an idea.

My guess is you are running on "limp mode".

If a car is idling at 1000 rpm when the engine is hot, that is the most likely case. You are also reporting that your ICV get's no power/voltage. That is another clue.

So before tackling other issues, you have to figure out why it is in "limp" mode.

Usually the OVP is the main culprit there. So take it out and check the date code on it. Also report on the brand.
Date codes are either actual dates or Work Week / Year.

The OVP is a silver 1-inch by 1-inch by 2-inch relay hiding behind the plastic cover behind the battery.

Congratulations on the purchase!
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post #4 of 5 (permalink) Old 03-20-2019, 12:05 PM Thread Starter
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Originally Posted by dolucasi View Post
Welcome to the forum.


Usually the OVP is the main culprit there. So take it out and check the date code on it. Also report on the brand.
Date codes are either actual dates or Work Week / Year.


Congratulations on the purchase!
It's a super fun little car!

Thanks for the advice to check the OVP. I pull it and report back, but I just ordered a new one. Found a $25 URO parts one on Amazon so I figured why not.

I checked the fuses a couple weeks ago and they were fine, so I figured it was something else, but I see now that the innards can fail, so I read up on what all the OVP does, and it made sense just to try a new one. If there's no change, I can return it.

Car has 167,000 miles on it and is a one-owner, but they had it parked it for the last 6 years or so and probably stopped actively maintaining it earlier than that. I'm pretty sure the car sat outside 100% of its life (in California, Hawaii, Oklahoma and Texas) because everything is pretty brittle. Seems like I break some little piece of plastic every time I touch the car. Today alone I busted the clips off the plug going to the ICV with barely any force.
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post #5 of 5 (permalink) Old 03-20-2019, 01:11 PM
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Ordering a URO OVP was not a good idea. You want either MB or KAE to avoid issues.

BTW if the car sat for so long it could even be the connections to the OVP at the OVP socket. So clean those well when you put in a new one.

Please report on the date code and brand of the one that comes out of there.
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