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

[Shayegan, Richard]

Well, I now know why the oil pressure is doing what it does. What I
don't know is why the engine is doing what it does to cause the oil
pressure to do...what it does. What's happening is this. I slow down and
pull up to the light. As I do this the engine rpms drop (as they
should), but instead of stopping at the proper idle rpm of 650, they
keep dropping to about 480rpm. Then after I've been stopped for a couple
seconds, the engine will surge, bringing the rpms up from 480 to the
proper 650. At the same time as the engine surges, the oil pressure goes
up to the proper level and the economy gauge goes 1/6 of the way out and
back. Sometimes it won't surge, it will just keep the pressure low and
the rpms down at 480 and the engine will run a little rough, but 90% of
the time it does the surging thing (I didn't notice it before because I
was looking for the rpm gauge to go up from normal, not up TO normal).
So, any ideas why my idle speed is low (albeit usually self-correcting)?
Also, I checked the oil again. It's just below the max line and
looks/feels like brand new oil (I guess the fact that almost all of the
miles have been highway kept the oil clean).
Thanks,
Richard

-----Original Message-----
From: mbcoupes-bounces at mbcoupes.com
[mailto:mbcoupes-bounces at mbcoupes.com] On Behalf Of
eurotech1 at charter.net
Sent: Sunday, January 23, 2005 9:58 PM
To: Mercedes Coupes Mailing Lists
Subject: RE: RE: [W126 Coupe] 1- doesn't start in cold 2 - oil pressure
strange


Hi Richard,

  It would be worth trying 15W40, just to see if there is any change in
your pressure when coming to a stop. We use Shell Rotella 15W40 in all
the Porsches (Porsche recommends Shell, and is the oil they are shipped
from the factory with)and also the Mercedes, we service at our shop.
It's a good oil that has done very well for us on the track (Solo 2
autocross), and has done well in our personal cars, so we recommend it
to our customers ( with the exception of some close-tolerance engines in
the later cars which require 5W30, we use Mobil One in those ). You are
in an area that gets a good deal colder than it does here. We
occasionally drop into single digits for a couple of days or so, but
Knoxville generally averages in the 30's and 40's most of the winter
(usually from late November 'til about early March), so I haven't had
any first-hand experience with really cold temps and oil pressure
problems. Try the 15W40 and see what happens, then go from there. It
won't cost much,!
  and it might solve the problem. 

                  Christopher Huffine