95 C280 Stalls out and/or very weak acceleration

[Robert Hageman]

My recently purchased C280 stalls, and/or spits and coughs when I try to accelerate. It's also very weak in acceleration. After doing this for a week or so, it stopped doing it and I was lulled into a false sence of security until it started happening again a couple of days ago only this time the 'check engin' light is glowing as well. I've done nothing accept change the fuel filter. That seemed to help some but the problem is still there. Thanks, Bob H

[mbdoc]

Sounds like the engine is running very lean! IF you have the check engine lamp computer scanned for codes & there is a code P0 170 fuel trim or P0 105 air mass sensor code, you will need a new air mass sensor. MB part number 000-094-05-48(list IS $355 & $255 REMAN).

[Robert Hageman]

I just this hour return from my mechanic (non-dealer) and he reports that he's getting a code 31. Apparently this at least in part agrees with your assessment because it mentions in the text that the car is running too lean.
It gets more complicated for me at this point because he then said that he was confused as well because he couldn't clear the code. I hope you know what that means because he tried explaining that he should be able to tell the computer to clear that code and he wasn't able to do that. So I asked what's next? He said that he had to check every code individually and that was a very time consuming processs. That sounded like a code for expensive and had him button it up until I could submit this on this forum. Here it is. Is there any hope?
Bob H

[Benzmac]

Be sure he has a digital code reader. This will have the live data you need. If he doesn't, go to someone else.

[mbdoc]

The overvoltage relay is a key part BUT doesnt cause this type of running problem. OBD2 code would be P0170, I have no idea what code 31 means.

[Robert Hageman]

I'm still vacilating about what to do. If you have no idea what a code 31 is then it really it really casts doubt on my technician's credibility. I have'nt asked him if his computer is digital but he did assure me earlier that it's the latest state of the art analyzer. I'm not really in the mood to spend another $225 to another tech another, independent analysis, but it looks like either that or take a chance on a O2 sensor which seems to come up in these discusions. I hope I can afford to be in the company of MB. Bob H

[David C Klasse]

I went to try and see if I could find out what Code 31 meant... and on an M104 motor (93-97), it said that code 31 was Not Used. This might not necessarily be the correct info though. Try searching yourself and see what you come up with...

http://www.autolib.diakom.ru:8000/CARS2/pribor/cs1000/manual/cs1000_mb.pdf

You can also try searching at http://OBDII.com and see if you can come up with anything... although I'm having trouble searching, I think because you need the full code.

Anyway, good luck, and keep us posted.

[Robert Hageman]

My mechanic (technician these days) says his computer is digital and that the machine tells him it's code 31 . He also mentioned something about 035, - fuel adaptation too lean. Not being a native, he's kind of hard to understand sometimes. He insists on his interpretation and acts as if he knows what he's doing but not being able to get any confirmation from the forum is very unnerving. I'm going to have to make a move at some time soon so I hope you will all keep trying to come up with a good course of action for me. Thanks Bob H

[mbdoc]

Bob, sounds like he is reading the codes from the fuel system computer!! NOT the diagnostic computer that registers the check engine fault codes. There is a code 31 in the fuel computer & that is for a faulty front O2 sensor. & code 35 means that the fuel system is too lean. HAVE him scan the DM (diagnostic ECU) at pin number 19 to get the correct check engine info!! STILL sounds like a faulty air mass sensor!! VERY easy to install, less than 5 minutes.

[Robert Hageman]

Thanks MB Doc, you've given me a starting point. One more thing please. When I went to the parts shop to check on an air mass sensor the only item that came up was a air mass meter. Are they the same thing? Is it possible to get a part numbe just to be sure? Thanks again, Bob H

[Benzmac]

Yes they are the same. There is only one on your car.

[Robert Hageman]

I think I'm ready to dive in. Replacing the air mass sensor is a fast and easy job. I'll take your word on that. But before I put out the $250 for the part, could you describe briefly what's involved, where is the part I'm looking for, and anything else that I may need to know? Adjustments, etc. I'm not a total idiot mechanically but it doesn't take long in these newer engines for me to feel like one. Thank you for your patience and your help. Bob H

[mbdoc]

The air mass sensor is mounted in the air charge tube just about 1 foot from the air filter assembly. 1 hose clamp & 2 quick release clamps. The electrical connection comes loose by twisting CC/wise. Iposted the CORRECT part number on the first reply-000-094-05-48 or 000-094-05-48-88(reman).

[Robert Hageman]

MB Doc
Well I finally bit the bullet and replaced the air mass Sensor. I wish I had better news to report. The 'check engine' indicator still comes on. Although I've only driven the care for a couple of miles since replacing the part, it does seem to run better. (a little slugishness at first but, I assume that can be accouted for by the fact that it's been sitting for a week or so) I hope it's not just wishful thinking.
Any other thoughts about the 'check engine' indicator? Thanks, Bob H

[mbdoc]

The check engine lamp must be scanned to shut the lamp off, also after replacing the part you must drive at least 40-50 miles before the correction factor will return to normal!! You can turn off the lamp by removing fuse 31 or 32 (dependant on production date of car) with the key removed. IF you feel that the engine has better performance then you are on the right track.