Idle control valve problem

Hi, well Jens got me on the right track to check this valve. Indeed it is not right. When I pull the electrical connection the engine dies within a short time (a number of seconds). According to BenzWorld, it should have
increased the idle rpm (an indication the valve is good). I'll be pulling this valve off and cleaning it... however, is the engine stalling a specific sympton for anything while I'm in there? with the electrical plug connected the engine revs at 500 when in gear and around 700 when in P or N the idle also is not 'particularly' smooth, not bad - but there is a bit of surging.
cheers, guenter
ps DIY's have -got- to love the internet
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What car do you hafve again?
That idle speed is normal for most cars... Smoothness is usually affected by vacuum leak.
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It's a '89 300E, when I pull the idle control valve plug the engine stalls in short order. For a correctly operating idle valve, apparently, it will rev up to 1500 rpm or so. Presumably the idle control valve is open when there is no power applied and the ECU closes it to an appropriate value. What suprises me is that the engine actually stalls when I remove the power to the idle control valve. Possible I've got things wrong. Anyone know for sure?
cheers, guenter
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I don't say that the valve does not work. Apparently it just works too slowly.
Or mixture is too lean, which gives engine problems to catch up when ordered to.
Vacuum leak among other things will give lean mixture, since more air is drawn into the engine than measured by air mass sensor.
Guenter Scholz wrote:

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Jens, thanks. Indeed, you did not say valve does not work. Posters on 'benzworld' say that for a correctly operating idle air control valve the engine rpm should increase to around 1500 rpm if the valve is diconnected from the ECU and the valve is operating correctly. In my case the engine stalls. I notice that Roland Francius is suggesting, in contrast, that the engine typically stalls when disconnected from the ECU.... I'm a bit puzzzled consequently at this moment.... For certain, I believe, my idle control valve will not suffer from some cleaning to see what effect that will have.
cheers, guenter

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The idle speed air valve opens fully when 12 volts is applied to it, which is the case when starting. When the desired idle speed (approx. 650 rpm) is reached, the ECU will lower the voltage to stabilize the idle speed. When the plug is disconnected, it will go to its opposite outer position, in which it will open again to provide at preset throttle (factory preset, don't adjust).
The fact that it stalls, when the plug is disconnected, indicates too lean idle mixture.
Check whether the two hoses to the idle speed air valve are tightly fitted, particularly the one leading to the air mass meter body (the top part). If false air is drawn here, the idle air will not be measured correctly by the air mass meter, causing the engine only to get more air but not more fuel, when opening the idle speed air valve (and consequently stalling and hunting idle speed).
Guenter Scholz wrote:

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I had the same problem on my W203 200 kompressor Year 2001. I just replaced the old Idle control valve plug and it works perfectly ;-)
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