Ditto, please keep the personal attacks away.
We are only trying to help each other here.

By the way, I ordered some parts today from MercedesShop, I have never heard anyone sending stuff overnight for $9. Isn't this forum great?

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1999 Porsche 996 Carrera Convertible
1994 420E - SOLD
1986 300E - SOLD, what a car
609 Certified

Yes,
definately keep those personal (RUDE!!!) attacks away, this is a forum of people trying to help people. With the exception of the experts... Steveb and the others, I would say the rest are nothing close to experts. So information, information, information is a good thing.

Sorry folks the person who put in that rude comment needs to be put into his/her place.

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**A few Hondas etc... etc... Not Worth Mentioning**
83 Euro W126 380 sel Money Pit (Sold)
91 W124 300e 2.6. (Sold) 3.0 Motor is Much better!!
93 BMW E34 Touring Wagon (Sold) Sweet Car!!
91 300e (Just 200k with Ease.)Best car ever ???(Sold)
90 420sel (Black with Tan Interior) Best car ever!!!!!!!

Sorry to disappoint but I was unable to check what the sealed screw would do. It was stuck so tightly that the brass key socket stripped when I tried to open it. Steel won out over brass, so I guess it's not meant to be adjusted after it leaves the factory

However, I was able to test the old Idle Control Valve, which miraculously started working once I got it on the bench. Perhaps there was a bad connection or there's a connection fault within the unit. Either way, here's my observational guesswork:

Firstly, at no voltage, the shutter valve defaults to a position of about 1/4 open, which is around 2mm. I'm presuming, based on my experience, that at this setting, you get an idle of around 500 rpm, which is enough to start the car and can produce an acceptable idle speed if the mixture is adjusted, but not enough to keep the motor running when you close the throttle, which causes the stalling effect under deceleration.

Note that the default mode is the rest position of the shutter, and I reckon the adjustment screw sets this position. I tried to move the shutter which a screwdriver while at this position but could not. I incorrectly assumed this meant the shutter was stuck but in actual fact, I was trying to push against the stop. In the diagrams that follow, the screw is on the top and logically prevents the shutter from opening any further than the rest position. When powered up, the shutter opens downwards, in the other direction which closes the default gap and opens from the other side of the airway.

FWIW, I cleaned a considerable amount of black gunk out a few weeks ago and was rewarded with a shiny, albeit worn, shutter. However, when I looked at the shutter under power, I could see that the 1/4 section which remains hidden in rest position was still black as anything. Perhaps using cleaner while powering up the valve would be more effective.

I've attached five images showing the position of the shutter at voltages of 0, 4.5, 6, 7.5 and 10. These were applied from a transformer and read while the leads were connected to the ICV. When I took readings directly from the transformer, these translated as follows: 4.5 read from the ICV connections = 7.5v when read directly from the transformer; 6v read as 9v; 7.5v as 11v and 10v as 15.6v.

This I presumed was due to the resistance of the ICV, perhaps due to bad internal connections. My physics is a little shaky at this point as its been years since I've had to think about it, perhaps someone more knowledgable can shed light on this. If the ICV responds to exact voltage settings, and is sapping the power along the way, perhaps explains why the unit doesn't work as well as a good one. I could, of course, go get the new unit off the car and test it but I don't think so, not just yet while its working fine.

Anyway, hope this info is helpful and also hope that someone can verify my guesswork as to what's going on. I'd like to think I was right in replacing the unit and didn't get caught out by a bad connection. Certainly solved my problems, so whichever way I got there was good enough for me.

While I've got the floor, I would also like to say that this forum is easily the best of all the sources of Benz info out there in cyberspace. Apart from all the rough idle info, it was here I found out I needed to replace two capacitors to get my clock working again - what a blast that was. Thought I'd need to lay out for a new unit and ended up spending 1,000 rupiah, which these days, I'm afraid to say, is just 9.5 cents in real money.

Good work fellas!

Attached Thumbnails

 

position at 7v

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position at 6v

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position at 4.5 v

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position at default, 0v

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Simmo300e

Thanks you for the exloration you made.

I am sorry that you could not move that screw to see its function.

If I understand correctly, when at idle or at engine OFF, the shutter is in the default position.

Unfortunately I do not have a non working ICV to open it and see what the inside looks like.
I know from some drawings I have seen there are 2 bearings and one spring that could fail (+ other electrical devices indeed) and I suspect them to fail with ageeing.

Would you have the interest to open the ICV I would be interrested to have some pictures and try to imagine if the ICV would be reparaible.
I am convinced that it is interesting to know how these smart and expensive device work to unsderstand how to repair.

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Keep us posted especially if your problem is solved
Present cars:
My car: E-class 420CDI, 2008, W211, V8, 180 000km

Wife's one: C-class 220CDI Sport Coupé, Euro, 2002, W203. 345 000km

Son's one: GLK class 220CDI, 2009, W204

Sold E class 260E, W124, 1988 beloved car sold after 489 000 kilometres of reliable services (engine M103, clutch and 5 speed manual gear box all original).

E-class, W210 320CDI, 2000[/B], 225 000km, Sold

I think if you reread my earlier posts you'd understand that the rest position with engine off is different to the default positon when the engine is idling. It's that difference that seems to cause the stalling.

As for taking the unit apart, it looked pretty much sealed to me so I binned it. Sorry.

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1987 300e manual 250,000 km (sold)

My car has the idle control valve that works by heat soak from the cylinder head and I've got one of the electronic ones that I want to fit. Everything seems straightforward to plumb it in but the new one has three electrical pins and my old one only has two. So- can anyone tell me what the extra pin is for or how I could wire this up?
Thanks