[W126 Coupe] idling issues

[Richard Hogarth]

Dan, 
Many thanks for the kudos and thank you for sharing your experiences below
in your last email. Now you have hit on something that I can't solve with my
560: high idle. The car idles fine when the ambient temp is below 55-60f and
the car is cold. As soon as the temp gauge hit a hair above 80c, 
the idle in park sits at 1500 and sometimes at 2000. OUCH! That should
really raise hell with the life of my transmission, not to mention the
entire drive train. 
I have changed all suspect vacuum lines, temp senders, and all new fuel
injectors plus seats and seals. I have had the mixture checked and adjusted
about 1 dozen times. I was also told  that it's within usable spec to which
I say Bull. Please tell me more about removing the Y tube from the air idle
valve. 
I have not changed that valve but my local MB shop said that it's still
good. I've checked, tightened and siliconed every possible place where there
could be a vacuum leak, I even capped off the brake booster line. I've
cleaned all of the relay and fuse contacts under the hood. Fuel pressure is
good although the system does require extra starting/cranking time if I let
the car sit for more that 2 days. 
I'm miffed on this one. 

Happy Passover and Easter to all, 
-RPH

-----Original Message-----
From: mbcoupes-bounces at mbcoupes.com [mailto:mbcoupes-bounces at mbcoupes.com]
On Behalf Of Dan Gardner
Sent: Sunday, April 08, 2007 8:33 AM
To: mbcoupes at mbcoupes.com
Subject: Re: [W126 Coupe] modulator adjustment

Hi Folks

    First off,thanks to Dick & Richard for their invaluable help,I have not 
yet road tested the car but fingers crossed I am hoping for a smoother 
change across the shifts.
    This is the first car I have owned where I had to admit defeat and take 
the car to a German factory trained specialist with 40 yrs experiance. It 
would mysteryously refuse to start and once cut out possibly once every 
three months of use.Each time after an expensive tow home I would get it to 
run although not really analising what the problem was(fuel pressure and 
delivery rate ,sparks to spec) and in the process I picked up a high idle 
and had to remove the 45 deg tube from the air idle valve.
    The guy had the car for a week and telephone me to say he could not find

anything wrong and that the idle was high but still within specifications 
when in "Drive".
Adding there would be a charge but not the amount of actual time because he 
could not find anything wrong.

    When I went to collect the car he attached a meter to show the RPM in 
"Drive",his jaw dropped when I went to start the car and I refused to run,he

frantically checked fuel pumps,pressure and sparks with no luck it all 
looked good
    .I said I would leave the car and despite his embarrassment I was glad 
it happened there and not again on the road.He phoned me a day later saying 
that he had spent a lot of time to discover that the E.H.A had gone 
intermittent and that it was going to get me home but required changing.I 
have now fitted a new one and hopefully,fingers crossed the curse of being 
stranded miles from home will be a thing of the past.
    The first time it happened I had a small fuel leak on one of the pumps 
so a fitted two new ones plus a filter,it would not run and I could hear 
bubbles in the tank when the pumps were running so I clamped off the fuel 
accumulator,and I had bridged the pins on the fuel pump relay,it then ran so

in went a new accumulator and it ran but when the f/p relay was put back it 
refused to run so in with a new fuel pump relay and it purred like a kitten 
for 3 months and then died in a small town a long way from home.Needless to 
say the tow truck driver cheered me up no end by telling how many "Benz's" 
he had hoisted on the back of his truck and raving on about how 
reliable"Toyota's"were.The next tow guy said more or less the same thing 
adding "if you weren't driving a "Toyota" you needed your head examined!
    Truth is if we were all driving super reliable cars,well barring 
accidents,these guys would be out of a job.


 

                Kind Regards  Dan Gardner 1986 560 SEC euro (220kw) 

The MB Coupes Website!
W126 SEC Mailing List
Postings remain property of MB Coupes, L.L.C.