1992 400e
I have had this issue for the past 6 months where I will be driving along on the freeway and my car will surge sometimes light and sometimes hard. The bad part is sometimes when driving for a bit (car is warmed up) I might get stuck in traffic and the car will die when I come to a stop. Now this happens very randomly and for the most part I drive 50+ miles a day with maybe one to two hiccups. The rest of the time the car drives great and idles smooth. Originally I thought it was a fuel issue and cleaned out my fuel system a few times. I eventually traced it to thinking it was my mass air sensor a few months ago and bought a new bosch unit. That did not fix the issue. I later replaced my spark plugs. I have also checked for vacuum leaks and tested out my coils. I replaced my wires and o2 sensor two years ago so I do not suspect them. Oh and I replaced my main harness a few years ago.
Now throughout this all I occasionally get code 10 "voltage at mass air sensor too high/low" that pops up on the diagnostic module. I just tested the LH-SFI and get code 4 which is "voltage at mass air sensor with hot wire. open or short circuit". Is this new Mass Air sensor bad? or could there be anything else that could be making me run this code?

When the engine stalls under decel, will it restart immediately OR does it need to sit?

Cleaning the throttle butterfly can help that type stalling issue.

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MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

Thanks for chiming in MBDoc. It restarts immediately. I just cleaned out the throttle body yesterday. Took it for a spin. It didn't die but it did throw the same code again after driving. The thing I am wondering is if it can still throw that code 10 even without it actually being the mass air sensor. Let me know. I have been thinking that just the fact that the car dies could still make that code show up. I just don't want to be messing around trouble shooting other things when all it could be still is the mass air sensor.

BTW, I just picked up another used throttle body yesterday and getting very close to swapping mine out just to test this one. I just don't want to do the work yet of swapping it if you don't think that it could be the throttle body.

Both code 10 from the DM at pin # 19 &
code 4 from pin # 4 indicates a defective air mass flow sensor!

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

Thanks MB DOC! I just wanted to confirm this information since I just bought the mass air sensor a few months ago from my local german parts shop. I spent a lot of time trying to diagnose this situation and I ruled out the mass air sensor only because I just bought it. So this morning I went out to my car and grabbed a mass air sensor I borrowed from my friend and just threw it in the car. Well, I took the car for a 20 minute spin and so far so good. I got home and ran the codes and no code showed up. The car was a lot more zippier too. I will take the car to work today which is typically about a 70 mile drive and see what the car does. Now I just hope that my warranty on the mass air sensor is still valid. I will post again if the problem comes back.

On another note. After owning this car for the past 6 years I can say that it's finally a relief to finally get this code reading thing down. I am glad that this community is here. My only wish is that I wish that there was a lot more info out there on the 400, 420, and 500's out there. Or at least a specific board for my car.

Follow up....I drove the car about 100 miles today and not a single error code or surge. I am falling back in love with my 400. This week I also accomplished a few other tasks after visiting the junkyard last week. I installed used windshield washer motors. I now have functioning windshield squirters. I installed a used hirschmann power antenna. I can now hear radio stations. I installed a used heater control valve. I now have a heater that works whenever I want it too. I replaced the clutch fan which I kind of messed up last year but was still usable. I replaced the switch to adjust my passenger power mirror. Wow! What a week. I love the junkyard. I even picked up extra coils and ETA just in case mine ever go bad.

Well, I just want to say again. Thanks mbdoc!