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
ps DIY's have -got- to love the internet
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
I don't say that the valve does not work. Apparently it just works too
Or mixture is too lean, which gives engine problems to catch up when
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:
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.
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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