1992 W124 M103 2.6 idle problem - Mercedes-Benz Forum

LinkBack Thread Tools Display Modes
post #1 of 1 (permalink) Old 07-18-2011, 07:08 PM Thread Starter
Lifetime Premium Member
LeftCoastGeek's Avatar
Date registered: Jul 2011
Vehicle: 1993 300CE Cabriolet (mine) ; 1994 E320 Wagon (wife's) ; 1990 Benz 300E 2.6 (spare)
Location: S'Cruzin Around on the Left Coast
Posts: 4,639
Mentioned: 8 Post(s)
Quoted: 851 Post(s)
Lifetime Premium Member
(Thread Starter)
1992 W124 M103 2.6 idle problem

I'm being given a 92 300E 2.6 with only 50K original miles. Its was a driveway queen for years, belonged to a friend's elderly Aunt who couldn't drive any more shortly after she bought it new. Apparently that friend, and another friend who has it now, have gone the rounds on trying to fix this idle problem, seen various benz mechanics etc.

The car idles really roughly. it stumbles badly around the general vicinity of 600rpm, and it will stall when you give it gas if you don't get it just so... but once its moving, its 100% fine, strong power up to the redline.

Its throwing code 4, which is the Air Flow Potentiometer. And when we put an ohmmeter across pins 1-2 or 2-3 on this pot, we read erratic resistance as you gently depress the air flow plate. 1-3 reads constant resistance. My friend replaced the potentiometer with an ebay part, but it had the same problem... the replacement part didn't include the wiper assembly, he thinks that maybe thats bad and its not replacable.

The wiring is in good shape, I don't see any crispy insulation anywhere. We cleaned the fuses (and yeah, I know, we should just replace them all on principle), even pulled the ECU and its connector looked hermetic, but we contact cleanered it anyways.


Q1) does it sound like we need to replace this air flow sensor plate assembly which I believe is benz part# A1030740114 ? or what ?

Q2) Whats the "MAS" box next to the ECU behind the battery that has the "1" "0" switch on it? I read that its a combined fuel pump and AC relay, but I couldn't find anything about the switch on it, what it does?

Even tho the paint is rough on this car (champagne color, the clearcoat is completely gone, the roof looks silver) and there's a few minor dents (trunk lid, driver door), the trunk is dry and the door has no wind leaks. the interior is really nice for a 19 yr old car, both front seats and the dash and door panels are like new. the package shelf and top of the back seat is sun bleached, however. I test drove the car over some Monterey back roads and it handles and drives great, smooth ride over some gnarly bumpy roads, very poised in control suspension, and awesome smooth powerful brakes. But stalling in traffic is bad, and its way too prone to it.

My friend is giving this car to my 16 yr old daughter as he doesn't need it, hasn't driven it in a couple months. its got no real cash value between the exterior and mechanical problems, we'd be lucky to get $1200 for it, but its too nice of a driver to let go to waste.
LeftCoastGeek is online now  
Sponsored Links

  Mercedes-Benz Forum > General Mercedes-Benz Forums > General Mercedes-Benz

Quick Reply

Register Now

In order to be able to post messages on the Mercedes-Benz Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:


  • Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
    Thread Tools
    Show Printable Version Show Printable Version
    Email this Page Email this Page
    Display Modes
    Linear Mode Linear Mode

    Similar Threads
    Topic Author Forum Replies Last Post
    HELP with 1992 w124 shifting problem DADARKPRINCE W124 E,CE,D,TD Class 8 06-28-2016 07:29 AM
    300e W124 M103 engine, fuel pressure regulator problem? up2nogood W124 E,CE,D,TD Class 3 04-23-2014 06:24 PM
    Engine swap 1992 230e M102.982->M103.940 Automotive W124 E,CE,D,TD Class 5 06-25-2010 09:39 PM
    M103 Idle problem, I've done some digging... questions akimball442 W126 S,SE,SEC,SEL,SD,SDL Class 18 06-12-2008 06:29 PM
    M103 Bumpy idle wbrauer W124 E,CE,D,TD Class 1 07-27-2003 05:43 PM

    Posting Rules  
    You may post new threads
    You may post replies
    You may not post attachments
    You may not edit your posts

    BB code is On
    Smilies are On
    [IMG] code is On
    HTML code is Off
    Trackbacks are On
    Pingbacks are On
    Refbacks are On


    Title goes here

    video goes here
    description goes here. Read Full Story
    For the best viewing experience please update your browser to Google Chrome