Lifetime Premium Member
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
Mentioned: 8 Post(s)
Quoted: 851 Post(s)
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.