[W126 Coupe] rough idle

[Tim Graney]

yes I replaced the injectors and yes to regulator and fuel distributor.
I removed all the federalized stuff. Wires are new...what heat range of
plug would you recommend? Thanks in advance Jonathan.

-----Original Message-----
From: mbcoupes-bounces at mbcoupes.com
[mailto:mbcoupes-bounces at mbcoupes.com] On Behalf Of Jonathan
Sent: Thursday, August 09, 2007 9:58 AM
To: Mercedes Coupes Mailing Lists
Subject: Re: [W126 Coupe] rough idle


Tim Graney wrote: 


Here is a question for all you guru's out there. I have a 1985 500SEC
Euro AMG which I have pretty much replaced every top part on the engine
and it still idles rough when it is cold . I replace all the elements
that control the idle. The box, the valve, the fuel controller, warm up
regulator. It starts right up and idles to around 850 RPM nice and
smooth then starts to stumble a little bit like it is running fat. It
runs fine once you take off but stumbles a bit unitl it reaches
operating temp. As soon as it reaches 80C it smooths out and runs and
idles perfectly at 500RPM. I replaced all the sensors on the motor. The
only two I have not replaced are the two thermo time switches. I also
did the heads and replaced all the hydraulic compensators and lash caps
along with all new valves and springs. I just cleaned the the surface of
the heads about .002 to give a nice mating surface. All the wires have
been replaced. New Cap, New Rotor. I have adjusted the fuel mixture ad
nauseum. I use a vacuum gauge and a exhaust gas analyzer and like I said
it run tits when warm but crap when cold. Any Ideas?


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I didn't notice injectors in the above list..

When you say fuel controller, do you mean the regulator or the fuel
distributor?

What spark plugs are you running?  Did you check the wires to be Sure
they're spot on (anything beyond 1.2-1.3 Kohms I consider bad).

I would go ahead and replace those thermo time switches, they're cheap
and easy.

Has this car been federalized (I'm assuming you are in country).
Sometimes they install O2 sensors and frequency valves and once they
fail can lead to issues.

Jonathan



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