[W126 Coupe] Opinion on ignition parts & dust cover

Thu Sep 15 18:15:21 EDT 2005

While there are two different Richard's at work here (and the earlier questions were presented by the other Richard), I'll add that apparently your issue is different from mine. Mine just comes and goes as it pleases without rhyme or reason (other than that gunning it in neural can make it go away) and it gets smoother in N than in D.
Richard S

-----Original Message-----
From: mbcoupes-bounces at mbcoupes.com [mailto:mbcoupes-bounces at mbcoupes.com] On Behalf Of Tom Oelsner
Sent: Thursday, September 15, 2005 6:02 PM
To: Mercedes Coupes Mailing Lists
Subject: RE: [W126 Coupe] Opinion on ignition parts & dust cover

Richard,
There is no separate check engine and O2 sensor light.  As for your earlier
questions regarding idle, I just got back from some highway driving.
Results are:
1. When car has been driven for some time, when stopped for a light the idle
is pretty smooth in drive (but not always).
2. AC vs. non AC has no or negligible impact on above.
3. When car has been driven for some time, when stopped for a light the idle
is much more rough when in P or N.
4. AC vs. non AC has minimal impact on 3.

Tom

-----Original Message-----
From: mbcoupes-bounces at mbcoupes.com
[mailto:mbcoupes-bounces at mbcoupes.com]On Behalf Of Shayegan, Richard
Sent: Thursday, September 15, 2005 1:36 PM
To: Mercedes Coupes Mailing Lists
Subject: RE: [W126 Coupe] Opinion on ignition parts & dust cover

This car has separate lights for check engine and 02 sensor, no? The O2
sensor light is activated by nothing more than mileage (at least on pre-86)
and if it was ever replaced there is no more light bulb behind the O2 sensor
light (that was part of the repair procedure,  apparently because as it
turns out those O2 sensors do 120k before needing replacement typically, not
60k).

-----Original Message-----
From: mbcoupes-bounces at mbcoupes.com [mailto:mbcoupes-bounces at mbcoupes.com]
On Behalf Of Richard Hogarth
Sent: Thursday, September 15, 2005 3:24 PM
To: 'Mercedes Coupes Mailing Lists'
Subject: RE: [W126 Coupe] Opinion on ignition parts & dust cover

Tom,
I would bet that oil combustion products are getting deposited on the O2
sensor at idle and causing the chk engine lite to go on, then the hot gasses
burn off some of that junk at normal temp or higher speed then the lite goes
out.
If you are burning that much oil and at that engine age, the egr valve is
likely not sealing well and not operating smoothly, also prone to causing
and being effected by vacume leaks causing the chk engine lite to go on and
off. I'll get back to your plug issue later. Need to do some work.
(lol) -Richard Hogarth

-----Original Message-----
From: mbcoupes-bounces at mbcoupes.com [mailto:mbcoupes-bounces at mbcoupes.com]
On Behalf Of Tom Oelsner
Sent: Thursday, September 15, 2005 2:14 PM
To: Mercedes Coupes Mailing Lists
Subject: RE: [W126 Coupe] Opinion on ignition parts & dust cover

Richard,
Always smooth on startup, don't recall if it is after hwy or city (I'll try
and monitor over next few weeks), more prone to rough (not glass smooth)
when hot.  I am burning a lot of oil...definitely seals based on mechanic
feedback.  O2 was replaced about 20k miles ago.

Here is one for you...when driving at low speeds after car is first started
and coming up to temp (in the 40 degree C range) or has been sitting for a
period of time (but not necessarily cold), the check engine light comes on.
After a minute or 2 of acceleration, the light goes out.  Happens every
time.  Since nobody outside of the dealer has the error codes for a non CA
car and do not know the connector pinouts, they cannot access the code or
read it.  I have not had the time to research building a small LED readout,
connector pinouts and codes.
Tom

-----Original Message-----
From: mbcoupes-bounces at mbcoupes.com
[mailto:mbcoupes-bounces at mbcoupes.com]On Behalf Of Richard Hogarth
Sent: Thursday, September 15, 2005 11:47 AM
To: 'Mercedes Coupes Mailing Lists'
Subject: RE: [W126 Coupe] Opinion on ignition parts & dust cover

Tom,
Give us a little more,
Runs rough at startup, after stop and go,after being on the hwy, etc etc.
Does it run rough when the AC compressor cliks on? when it's hot or cold or
whatever.  On that age of engine, inconsistent small vacume leaks that come
and go with temperature and vibration changes are your biggest culprit. If
you are using some oil, a little more of less build up on the oxygen sensor,
or if the o2 sensor is not healthy may be the cause.
The ignition temp sensor in the intake manifold is also an item that can
cause rough running and idling.
-Richard Hogarth

-----Original Message-----
From: mbcoupes-bounces at mbcoupes.com [mailto:mbcoupes-bounces at mbcoupes.com]
On Behalf Of Tom Oelsner
Sent: Thursday, September 15, 2005 1:16 PM
To: Mercedes Coupes Mailing Lists
Subject: RE: [W126 Coupe] Opinion on ignition parts & dust cover

I never tried it but will next time it acts up Tom

-----Original Message-----
From: mbcoupes-bounces at mbcoupes.com
[mailto:mbcoupes-bounces at mbcoupes.com]On Behalf Of Shayegan, Richard
Sent: Thursday, September 15, 2005 11:12 AM
To: Mercedes Coupes Mailing Lists
Subject: RE: [W126 Coupe] Opinion on ignition parts & dust cover

I'm using W9DC's in my 380 and the only mechanical issue I still have I is
exactly the one you describe: sometimes it's perfectly smooth, but also
every now and then it idles a bit rough. No rougher than a non-German
engineered engine, but not as smooth as it is when it's running right. I
don't have any fouling, and I'm using the proper plugs, so if we do have the
same issue I don't think your plugs are at fault. Does yours also smooth out
if you goose it in neutral a few times?
Richard

________________________________________
From: mbcoupes-bounces at mbcoupes.com [mailto:mbcoupes-bounces at mbcoupes.com]
On Behalf Of Tom Oelsner
Sent: Thursday, September 15, 2005 1:58 PM
To: Mercedes Coupes Mailing Lists
Subject: RE: [W126 Coupe] Opinion on ignition parts & dust cover

I'm using Bosch, Platinum 2, R3.  Sometimes the engine idles so smoothly
that I am not sure it is running.  Other times it idles a bit rough.  This
is in spite of the fact that I have major oil fowling on at least 1 plug
(just checked one to confirm plug type.  I know I need the valve seals
done.).  Oh yeah, for what it is worth, the car was not originally a CA
car.  It was from Texas.
Tom
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