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

Fri Oct 28 09:49:37 EDT 2005

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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