[W126 Coupe] Intermittant Rough Idle -Me too - HELP!

Fri Oct 28 10:41:42 EDT 2005

Or just get it running rough, take a can of carb cleaner, and spray it
around each injector, when it smoothes out you've found your bad
injector seal. The temperature relation I think is because 65C is when
the cold start valve closes, so until then the cold start valve is
richening the mixture enough to smooth things out, then the engine gets
to 65C, the cold start valve closes, and you have a cylinder running
lean.
Richard

-----Original Message-----
From: mbcoupes-bounces at mbcoupes.com
[mailto:mbcoupes-bounces at mbcoupes.com] On Behalf Of Richard Hogarth
Sent: Friday, October 28, 2005 9:50 AM
To: 'Mercedes Coupes Mailing Lists'
Subject: RE: [W126 Coupe] Intermittant Rough Idle -Me too - HELP!

Richard, 
Yes, if I richen up the mixture enough the idle smoothes out but the
engine
bogs down just as you say. 
Its the consistency of the problem at specific temperatures that
confuses
me.
I'll take you suggestion, pull all the injectors and look for double
seals,
torn seals etc. 
-Richard Hogarth 

-----Original Message-----
From: mbcoupes-bounces at mbcoupes.com
[mailto:mbcoupes-bounces at mbcoupes.com]
On Behalf Of Shayegan, Richard
Sent: Friday, October 28, 2005 8:28 AM
To: Mercedes Coupes Mailing Lists
Subject: RE: [W126 Coupe] Intermittant Rough Idle -Me too - HELP!

Did you try really richening it up? When I had an injector seal leak at
one
cylinder (the new seal had been put on top of the old seal), it acted
exactly as you described, but richening it a lot would overcome the leak
(it
would also bog down the engine a bit). Also, do you know if the
distributor
is good?

-----Original Message-----
From: mbcoupes-bounces at mbcoupes.com
[mailto:mbcoupes-bounces at mbcoupes.com] On Behalf Of Richard Hogarth
Sent: Thursday, October 27, 2005 11:25 PM
To: 'Mercedes Coupes Mailing Lists'
Subject: RE: [W126 Coupe] Intermittant Rough Idle -Me too - HELP!

The MAF plate does not bind and seems to move smoothly and seems to have
the
right tension.
I've always thought that MAF plate problems had more to do with
hesitation
and acceleration. 
BTW- the compression is all within spec across the board. 
The car accellerates great, smooth as silk once it comes off idle, but
it
idles like it has 2 dead cylinders. 
-Richard Hogarth 

-----Original Message-----
From: mbcoupes-bounces at mbcoupes.com
[mailto:mbcoupes-bounces at mbcoupes.com]
On Behalf Of Shayegan, Richard
Sent: Thursday, October 27, 2005 8:37 PM
To: Mercedes Coupes Mailing Lists
Subject: RE: [W126 Coupe] Intermittant Rough Idle -Me too - HELP!

Well since it happens when the cold start valve closes I think you need
to
richen it, but you say it's not mixture, so maybe the MAF plate is out
of
adjustment?

-----Original Message-----
From: mbcoupes-bounces at mbcoupes.com
[mailto:mbcoupes-bounces at mbcoupes.com] On Behalf Of Richard Hogarth
Sent: Thursday, October 27, 2005 9:20 PM
To: 'Dwan'; 'Mercedes Coupes Mailing Lists'
Subject: RE: [W126 Coupe] Intermittant Rough Idle -Me too - HELP!

HELP!
When you figure it out, please let me know.
This has been a persistent problem
on my vdhicle and several others that I know of.  
I've tried nearly everything and I'm certain that I'm vacuume leak free.

On my car it occurs once the engine comes up to about 65-80 degress on
the
temp guage. 
On my vehicle it is totally temp related. 
I've done the inject seals, replaced the temp sensor, ignition module,
coil,
plugs, wires, swapped injectors, pulled the metal fuel feeder lines and
cleaned them out with a small wire and carb cleaner as was previously
suggested, changed the O2 sensor, replaced the exhaust manifold gasgets,
Checked for catylitic converter back pressure, replaced the fuel filter,
adjusted the mixture a million times, replaced all of the vacuume hoses,
t's, one way vacuume valves, checked the IAC valve, brought it to a
local MB
"specialist", (no dealer nearby), he is stumped; told me to live with
it.

So please HELP!
-Richard Hogarth

-----Original Message-----
From: mbcoupes-bounces at mbcoupes.com
[mailto:mbcoupes-bounces at mbcoupes.com]
On Behalf Of Dwan
Sent: Thursday, October 27, 2005 2:35 PM
To: Mercedes Coupes Mailing Lists
Subject: Re: [W126 Coupe] Intermittant Rough Idle

Possible vac leak at check valve,also idle control unit black
rectangular
unit on the fire wall on 126's

-----Original Message-----
From: Robert Cavazos <jazzman_390 at yahoo.com>
Sent: Oct 27, 2005 2:54 PM
To: mbcoupes at mbcoupes.com
Subject: [W126 Coupe] Intermittant Rough Idle

I need advice from the diagnostic folks.

My wife's '87 560SL typically has a silky smooth idle, lately however
after
the car has been running for about 30-40 mintes the idle starts getting
rough almost like a one cylinder is missing. It can get pretty bad
shaking
the car considerably. When the engine is revved, it seems the miss goes
away
but returns at idle. It does not appear to be related to engine
temperature
and ambient air temp is about 80. 

It also dosesn't appear to be realated to driving conditions as it will
occur with driving around town, and when coming to a stop after freeway
driving.

Background
The fuel injectors were replaced a few thousand miles ago, and I checked
the
plugs last weekend looking for anomolies. They all looked fine. I also
wiped
out the inside of the dist cap and rotor thinking there might be
moisture
inside due to a recent few days of wet weather. 

Any ideas what else to look at or try?

Bob Cavazos

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Postings remain property of MB Coupes, L.L.C.