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  #1  
Old 02-09-2019, 07:45 PM
85 DSEL's Avatar
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M103 idle adjustment??

I'm needing to raise the idle RPM a bit on my 260E. Anyone have a pic or a link that shows where this screw is located? Is it a 3mm hex?

Thanks
Dale

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1995 W124 Wagon

Dale

1995 E320 Wagon 185K
1988 260e Sedan 135K
2007 F-150 XLT 188K
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  #2  
Old 02-09-2019, 08:46 PM
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IIRC idle is computer controlled. If it isn’t right, check for vacuum leaks and idle mixture setting.

Sixto
98 E320s sedan and wagon
02 C320 wagon
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  #3  
Old 02-09-2019, 11:02 PM
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M103 idle adjustment??

Quote:
Originally Posted by sixto View Post
IIRC idle is computer controlled. If it isnít right, check for vacuum leaks and idle mixture setting.

Sixto
98 E320s sedan and wagon
02 C320 wagon


On an '88? I didn't think there was much that was computer controlled until a few years later. I may be sorely mistaken though

Dale

EDIT: I made a 1/4 turn CW (rich) on the EHA today and it made A TREMENDOUS difference in the way the car accelerates and starts! But now the idle is a hair too low - approx 500-600 RPM, sometimes it may fall below 500 briefly then come back up.
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1995 W124 Wagon

Dale

1995 E320 Wagon 185K
1988 260e Sedan 135K
2007 F-150 XLT 188K
2003 Harley Davidson FLTRI Anniversary 26K
-----------------------------
2006 BMW 330Ci 110K - SOLD

Last edited by 85 DSEL; 02-10-2019 at 12:14 PM.
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  #4  
Old 02-10-2019, 11:08 AM
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M103 idle speed is definitely controlled by the "e-part" of the KE system. There may be an initial adjustment, but I've never messed with it.

The initial mixture adjustment should be done by measuring the duty cycle and adjust if necessary. A search should yield many threads on the subject.

Since idle speed and cold start enhancements are controlled by the electronic unit that is supplied power by the OVP relay, a dead OVP relay will cause hard cold starting and idle speed problems. If the ABS light is on there is likely a problem with the OVP relay as it also provides power to the ABS electronics.

Duke
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  #5  
Old 02-10-2019, 12:13 PM
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Quote:
Originally Posted by Duke2.6 View Post
M103 idle speed is definitely controlled by the "e-part" of the KE system. There may be an initial adjustment, but I've never messed with it.

>>> Ok, I'll take that, however, these cars do not have the 'brains' to make minute adjustments to deteriorated fuel supply caused by age and wear on a thirty year old car. There is a lot of info not only here on this sight but elsewhere on the web - so much so that it is an almost daunting task for one seeking a small morsel of data on the subject. I thought I would take a chance that there might be someone with the answer looking on and I could be in my way. <<<


.....a dead OVP relay will cause hard cold starting and idle speed problems. If the ABS light is on there is likely a problem with the OVP relay as it also provides power to the ABS electronics.

Duke

>>> None of these symptoms are present. <<<

NT
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1995 W124 Wagon

Dale

1995 E320 Wagon 185K
1988 260e Sedan 135K
2007 F-150 XLT 188K
2003 Harley Davidson FLTRI Anniversary 26K
-----------------------------
2006 BMW 330Ci 110K - SOLD
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  #6  
Old 02-10-2019, 12:20 PM
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Agreed. That’s probably why California directed my ‘91 300SE to gross polluter smog stations even if it never failed a test. The M103 is a frustrating beast to tune when the fuel system starts to wear.

Sixto
98 E320s sedan and wagon
02 C320 wagon
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  #7  
Old 02-10-2019, 02:05 PM
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Quote:
Originally Posted by sixto View Post
Agreed. Thatís probably why California directed my Ď91 300SE to gross polluter smog stations even if it never failed a test. The M103 is a frustrating beast to tune when the fuel system starts to wear.

Sixto
98 E320s sedan and wagon
02 C320 wagon


Indeed they are! I've finally started seeing light at the end of the proverbial tunnel with mine though. It basically starts well, runs well, and now after that very small tweak of the EHA, the acceleration from dead-stop is better than I've experienced since owning it!

There's a guy from Australia I think it is, on YouTube (goes by MMWA) that I tend to watch his 'journey' with his later model W124 (92 or 93, maybe) and he has a video taping about the EHA adjustment and what a remarkable difference it has made for his car. And I believe in it he mentions a "3mm hex screw" idle speed adjustment that may or may not need to be tweaked after one makes the EHA adjustment. I'll have to go back and find that video to see if he actually shows where it is located. All I know at the moment is, my car idles very smoothly now, albeit a little slower, and acceleration is remarkably improved

Dale
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1995 W124 Wagon

Dale

1995 E320 Wagon 185K
1988 260e Sedan 135K
2007 F-150 XLT 188K
2003 Harley Davidson FLTRI Anniversary 26K
-----------------------------
2006 BMW 330Ci 110K - SOLD
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  #8  
Old 02-10-2019, 05:53 PM
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IIRC the adjustment screw accessed through the air cleaner is for idle mixture, not idle speed. It might change idle speed but that’s not what it’s for.

Sixto
98 E320s sedan and wagon
02 C320 wagon
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  #9  
Old 02-10-2019, 07:03 PM
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Quote:
Originally Posted by sixto View Post
IIRC the adjustment screw accessed through the air cleaner is for idle mixture, not idle speed. It might change idle speed but thatís not what itís for.

Sixto
98 E320s sedan and wagon
02 C320 wagon


Yes, that's my understanding as well...

I am going to leave things as they are since it's not THAT bad. Not sure if a low idle speed can cause spark plug fouling or not but if it starts running ragged I'll have to do something at that point.

Dale
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1995 W124 Wagon

Dale

1995 E320 Wagon 185K
1988 260e Sedan 135K
2007 F-150 XLT 188K
2003 Harley Davidson FLTRI Anniversary 26K
-----------------------------
2006 BMW 330Ci 110K - SOLD
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  #10  
Old 02-11-2019, 10:09 AM
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Pierre Hedary has a good video on his Youtube channel on the EHA found here:
https://www.youtube.com/watch?v=XclGM2RgDDo
Many good videos on older Mercs. He is an MB fanatic!
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  #11  
Old 02-11-2019, 08:22 PM
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Quote:
Originally Posted by rob300e View Post
Pierre Hedary has a good video on his Youtube channel on the EHA found here:
https://www.youtube.com/watch?v=XclGM2RgDDo
Many good videos on older Mercs. He is an MB fanatic!


Thanks rob300e, I follow him as well and have actually seen that video and it may be the one I have seen that mentions this illusive idle screw! So, thanks for posting it.

Yes, Pierre is a gem where these old Benz are concerned!

Dale
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1995 W124 Wagon

Dale

1995 E320 Wagon 185K
1988 260e Sedan 135K
2007 F-150 XLT 188K
2003 Harley Davidson FLTRI Anniversary 26K
-----------------------------
2006 BMW 330Ci 110K - SOLD
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  #12  
Old 02-11-2019, 09:48 PM
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That is actually one video I have seen that mentions this "3mm screw..." but Pierre doesn't disclose its location. Wondering if it is the one that is accessed from atop the air cleaner housing....? If anyone knows please let me know. Thank you

Dale
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1995 W124 Wagon

Dale

1995 E320 Wagon 185K
1988 260e Sedan 135K
2007 F-150 XLT 188K
2003 Harley Davidson FLTRI Anniversary 26K
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2006 BMW 330Ci 110K - SOLD
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  #13  
Old 02-11-2019, 10:08 PM
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The 3mm screw adjusts the main mixture, not the idle speed. Your idle speed should be electronically governed.
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  #14  
Old 02-11-2019, 11:06 PM
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Quote:
Originally Posted by Diseasel300 View Post
The 3mm screw adjusts the main mixture, not the idle speed. Your idle speed should be electronically governed.


It 'should'? If that's true, then it's not working. While the overall performance has been radically improved by the tiny adjustment to the EHA, the idle is maybe 200 rpm too low. THAT is what I'm trying to fix.

Dale
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1995 W124 Wagon

Dale

1995 E320 Wagon 185K
1988 260e Sedan 135K
2007 F-150 XLT 188K
2003 Harley Davidson FLTRI Anniversary 26K
-----------------------------
2006 BMW 330Ci 110K - SOLD
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  #15  
Old 02-11-2019, 11:37 PM
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Quote:
Originally Posted by 85 DSEL View Post
It 'should'? If that's true, then it's not working. While the overall performance has been radically improved by the tiny adjustment to the EHA, the idle is maybe 200 rpm too low. THAT is what I'm trying to fix.

Dale
Where is your idle speed at now?

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