Although it shares the same KE injection system with the 300, the 560 is a different beast entirely when it comes to idle stability. Mark

Sorry... my car is also a 300SEL. My username was from about 7 years ago.

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2004 Toyota Sequoia Limited 4wd
1991 Lincoln Town Car Executive
1991 Cadillac Sedan DeVille
1988 Mercedes 300SEL
1972 Chevrolet Caprice Kingswood Estate 9-passenger wagon
1973 Pontiac Grand Ville
(Prior MB's: 1974 240D, 1985 380SE, 1984 190D, 1993 400SEL)

While there was absolutely no data provided on why the plugs would improve the situation except that Japanese NGKs "NEVER" work in German cars, and that it'll just work... I swapped plugs and wires with my friend's 300E anyway. He has the H9DCOs. We both have the OEM Bosch wires, mine were somewhat newer than his.

And it solved nothing at all. Problem persisted on my car, and his car drove no differently either. It's not the plugs, or wires. Period.

I sprayed some carb cleaner around the injector seals and idle changed just a bit when I hit cylinder 4, but not that much to make me immediately think it was a leak. I'll run a couple more tests to see what else it might be. Holding the pedal halfway down while starting the car though makes it start really quickly, like 1-2 cranks, which would suggest fuel leaking into the cylinders when the car is off...

Yeah, some guys just get off on these tangents without any empirical evidence to support their biases. The correct non-resistor NGK plugs work just fine in the M103 motor, as do the correct Bosch, Beru and Champion plugs.

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1988 California version 260E (W124)
Anthracite Grey/Palomino
Owned since new and still going strong and smooth
MBCA member

Past Mercedes-Benz:
1986 190E Baby Benz
1967 230 Inherited from mom when she downsized
1959 220S Introduced me to the joys of keepin' 'em goin'

There are only 10 kinds of people in the world--those who understand binary and those who don't

you swapped your plugs with other used plugs? maybe this car is not for you....sounds like you are not liking this car....

It seems to be their 15 minutes of fame. Mark

I swapped to test your "theory." It proved wrong. My NGK plugs worked perfectly fine in the 300E. And the Bosch H9DCOs gave me the same symptoms. So, the plugs have nothing to do with it.

I like this car, but it is my beater. I don't mind spending money on it, but I'm not going to throw money away for no reason either.

Anyway, back on topic towards a resolution... Will be ordering injectors and a few misc. parts soon. Will see if it helps out the issue.

For a free test, you may want to give the EHA a small turn....I had a number of bottom end problems on my 260E that were completely resolved after I gave a 1/2 turn clockwise (rich) on the EHA. I recommend you write down exactly how far you turned and mark it so if you need to turn it back, it won't be a problem. Giving a 1/4 or 1/2 turn will raise BAR pressure in the lower fuel distributor chamber that just makes up for general wear and tear over the years throughout the system.

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2016 Monsoon Gray Audi Allroad - 21k
2008 Black Mercedes E350 4Matic Sport - 131k
2014 Jeep Wranger Unlimited Sahara - 62k
2003 Gray Mercedes ML350 - 122k

Sounds good. I think there is a "spec" to adjust it to right? 0.1mV?

Sorry I don't have an update yet guys, been working and playing with my other car lately... I have lived with the issue and it's not really bothering me enough yet. I will do the injectors though and will report back when I do to see if there are any changes.

My friend with the 1990 300SE has erratic idle when in gear. Sometimes the idle will go up and down and sometimes require harder braking when it idles up. Anyone know what causes this?

My bet is on the airflow potentiometer. There are a few people who sell them on eBay and here are the instructions to adjust it. I had the exact same issue and that fixed it for me.

http://sg-motorsports.com/AFS%20Pot%20write-up.htm

Any updates? Did you replace the injector seals?

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http://i193.photobucket.com/albums/z...-RESIZED-1.jpg
1991 300E - 212K and rising fast...

No sorry. I've been bad about it honestly... Been living with it and putting money into my track car instead. And there are two W203s in the household that are constantly giving me problems too.

It's a small issue to live with now. Maybe over the Christmas break I may attack it.

Bad P/N switch? Sticking ICV?

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A.S.E Tech A1,A6,A7,A8 & MVAC 609 + EPA 608

Unless stated otherwise, any question I ask is about my greymarket 1985 380SEL.