95 C280 Stalls out and/or very weak acceleration
 

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

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).

More information
 

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

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

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.

'95 C280 update
 

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

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.

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

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.

air mass sensor/meter?
 

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

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

Decision time
 

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

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).

Replaced Air Mass Sensor
 

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

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.

Thanks MB Doc. I think I'll drive it for a while and see if the light goes out on its own. Bob H

You only wish!
 

Robert,
The check engine light will not turn off on it's own. You MUST reset it. Do what MBDoc says (though I used to just unplug the battery... MBDoc's idea sounds better), and THEN drive it some more to see the results.
Again, the MIL will not go out on it's own. It MUST be reset!

Reality
 

I'm disappointed to report that apparently the air mass sensor was not the problem. After pulling the #32 fuse then reinstalling it the 'check engine' light did go out and it seemed to run better for a while. Now 60 miles later the light returned and the problem has also returned with a vengence. Same symptoms but worse. Let me elaborate on the problem and perhaps that will help.
The stalling seems to be at it's worse after the car has been warmed up pretty good. Then turned off for a while (5 to 10 minutes) then restarted. Tonight after going into a store, when I came back to the car it started fine and idled fine but when I tried to accelerate there was almost no reaction at all - the car just sat there. Finally I discovered that if I put it in nuetral and pumped the accelerator vigorously the engine would begin to rev and then smooth out and I could limp away. Then once under way it would run fine until I came to a stop and then it was de ja vous all over again. What do you think. Bob H

Catalytic converter?
 

Several years ago I had a 1982 Mazda 626 (since totaled) which exibited some of the same symptoms I've been referring to with the C280. It turned out to be the catalytic converter. Does this sound like a posiblility to anyone? Bob H

A 1995 C280's check engine light will not turn off on it's own. Sometime later, not sure of the year, they made it turn off after certain mileage if the problem had corrected itself. Although I strongly believe that 95s will not turn off. Correct me if anyone knows otherwise.

I'm sure you are right, David. That's what MB Doc told me but I misunderstood. Since then I've pulled that fuse and put it back. It went out for a while, but then came back on. I pulled it again and put it back and once again it's off, but for how long I couln't say. But the problem with the car is still with me. I hope you all will keep thinking about what I could try to do to fix it. Bob H

Getting close
 

Over all the car is running a lot better but not perfect. The 'check engine' light has remained off. I replaced the OVP. Now the only symtom I'm seeing is that maybe 25 or 30 percent of the time accelerating from zero, the car wants to hesitate then it seems to pass some critical point and then accelrate normally. If I don't let the car come to idle that is keep my foot on the accelerator just enough so that it keeps about a 1000 rpm, there is no problem at all except I don't like having to do that. Thanks. Bob H

More info about wiring harness
 

Thanks Black Mercedes. Could you elaborate a little. I took a quick look at the engine compartment , but didn't see anything that I could readily identify as a wiring harness. Where is it in a 95 C280 with a 104 engine? Should I be able to tell if it's wearing out (frayed or something obvious)? Are there more than one?
Also the parts dept. didn't seem to recognize the part called 'wiring harness'. Does it go by any other name? Thanks for your help. Bob H

Robert,
The wiring harness is all of the wires in the engine bay. The early 104 engines used poor materials where the wire covers would all flake off from the heat. This causes all sorts of random problems within the engine!! If you do a search, you'll come up with all sorts of information on this topic. IF you have 100k miles or less on your car, sometimes MB will replace it for free or split the cost. Are you the original owner of the car?
Cost is about a grand to have it done. Be sure and do a search, you should find a fair amt of info on the topic.
Inspect all wires in the engine bay for flaking covers! Good luck (or actually not, hope it's an easier fix than that...!)

carbon build up
 

I would also check the spark plugs for carbon build up - this also will cause some of the problems with poor acceleration, etc.

Cautiously optimistic
 

Hopefully this will be my last post on this subject. After spending $500 on analysis that told me nothing, an air mass sensor, and an OVP, I think the final solution was to clean the contacts on my spark plug connectors (I finally found where Mercedes hid them - under that panel thing on top of the engine) and make sure there was good contact being made. You're probably wondering why I didn't try that first. Me too! The car is running very well right now (better than even before I really noticed the problem). I believe I'm going to go ahead and change out the plugs anyway just because I don't think they've been changed before. I'm replacing them with the same kind that are in there now (Bosch C8DC4's I think) unless someone tells me that that's not a good idea.
Thanks for all the input. Bob H