'73 280SE 4.5 Intermittently running rich - Page 4 - Mercedes-Benz Forum

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post #31 of 35 (permalink) Old 11-09-2008, 01:57 PM
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Date registered: May 2007
Vehicle: 64' 220SEc, 72' 300SEL 6.3, lots of parts
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Map sensor adjustment

Counter intuitive,
Unscrew will lean total mixture,
Think of the MAP sensor as an altitude compensator,
that screw raises or lowers the "set" altitude of the entire system.
This analog system operates on the difference of vacuum / pressures.

No more than 1/8 of a turn per tank of fuel.
Add 1 Qt of ATF per tankful.

Also Idle mixture will need adjustment too.

I have spare MAP sensors for substitution and messing with so as to not disturb your original as-is calibrations..

Brian O
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post #32 of 35 (permalink) Old 08-06-2013, 12:00 AM
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Vehicle: 2006 C230 Sprots V6, 1972 280 SEL 4.5
Location: San Francisco, Ca
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Quote:
Originally Posted by bostosh View Post
Counter intuitive,
Unscrew will lean total mixture,
Think of the MAP sensor as an altitude compensator,
that screw raises or lowers the "set" altitude of the entire system.
This analog system operates on the difference of vacuum / pressures.

No more than 1/8 of a turn per tank of fuel.
Add 1 Qt of ATF per tankful.

Also Idle mixture will need adjustment too.

I have spare MAP sensors for substitution and messing with so as to not disturb your original as-is calibrations..
Hello,

I realize that this is an old post but I am having problems with the idling of my 72' 280SEL 4.5. I was curious to know what you mean by "No more than 1/8 of a turn per tank of fuel. Add 1 Qt of ATF per tankful." I feel that either the Idle control valve or air regulator of my W108 is faulty. My air regulator may be stuck and my Idle Control Valve may need cleaning. For the mean time, I've bypassed the air regulator by inserting a ball bearing from the hose that connects to air regulator to the idle control. It's a temporary fix pending the idle control valve cleaning. It has lowered the idle to where I can control idle via the idle control valve adjusting screw. The Oil pressure has dropped to 15 from 45 on the instrument cluster. I haven't tested gas readings as I don't have a gas analyzer. Hopefully a local smog shop can help me with this. Any help will be greatly appreciated. Thanks in advance.
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post #33 of 35 (permalink) Old 08-06-2013, 08:30 AM
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the pressure sensor [ map ] is the main fuel mix control together with the coolant temp sensor .a bad brain will cause engine to flood at time , usually when getting warm .i have seen cars with fuel running out of exhaust pipe ! . if you are in san diego , send me a phone number .
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post #34 of 35 (permalink) Old 08-07-2013, 08:38 AM
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disconnect the trottle valve switch , and see if problem goes away , you can drive that way for testing .i am in bonita .
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post #35 of 35 (permalink) Old 08-07-2013, 09:11 AM
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Date registered: Feb 2012
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Originally Posted by agillot View Post
disconnect the trottle valve switch , and see if problem goes away , you can drive that way for testing .i am in bonita .
I haven't tried that yet. I'm located in San Francisco.
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