[W126 Coupe] 1- doesn't start in cold 2 - oil pressure strange

[Shayegan, Richard]

One thing I forgot to ask: could this be mixture related? I'm never
convinced that I have that setting just right, though I suppose it
wouldn't just go out of whack for no reason either.

Richard

 

________________________________

From: mbcoupes-bounces at mbcoupes.com
[mailto:mbcoupes-bounces at mbcoupes.com] On Behalf Of
Ken.England at ipaustralia.gov.au
Sent: Monday, January 24, 2005 6:36 PM
To: Mercedes Coupes Mailing Lists
Subject: RE: RE: [W126 Coupe] 1- doesn't start in cold 2 - oil pressure
strange

 


Richard 

Part of your problem seems to be in the idle speed control, which may be
either intermittent or perhaps a little slow in its action, sometimes.
Your throttle may be closing just slightly too far when you lift your
right foot.  This causes a low idle.  From your postings over the past
few days it seems that this does not always happen.  The reason could be
some kind of mechanical binding created by dirt, gum or uneven wear
arounf the throttle etc.   

With low idle (480rpm) your oil pressure will also be a little on the
low side.  This is normal.  The "economy" gauge, actually a vacuum
gauge, measures the vacuum in the inlet manifold and the vacuum will
drop slightly as the throttle opens under automatic control (probably
just slightly too far) to bring the idle up to its setpoint of 650rpm.
It then closes slightly which increases the vacuum a little.  (This
small overcompensation is also normal in most automatic systems unless
they are very expensively made, it's sometimes called hunting.)  The
instruments are faithfully recording the goings-on under the lid.   

I have seen much the same thing in my car a year or so ago and if the
engine does not actually stall while you wait at the lights then I would
not worry too much about it.  Something that should be fixed but does
not need an emergency tow to the MB dealers to fix it immediately. 

I have no explanation for the oil pressure needle twitching with only
the ignition on except to suggest that if it occurs while you move
around inside the car than there is probably a loose wire in the system
somewhere.  OTOH it remind me of the fact that if you turn a flashlight
on and leave it the light output will sometimes flicker even if you are
not touching the flashlight at that instant to disturb the connections.
That sort of thing may be characteristic of battery systems.  Otherwise,
(1) You're looking too closely.  (2)  The car needs an exorcism. 

Ken England

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