About a month ago I replaced my MAS in my 2000 C230k. I got the CE light warning; confirmed the error code and replaced it. Being that it was the original (replaced it at 97000 mi), I did not think much of it's (the original's) condition.

Well a month later, I have other performance issues: Often my supercharger just turns off. The car has experienced worsening hesitation. I've done hours of forum research and repalced, plugs, fuel filter, fuel pressure reg., air filter...

After changing out the fuel pressure reg (today), I got no better results. BUT I noticed something that caught my eye; my month old (new Bosch) MAS had oil around the out side of the base. So I take it off and WOW it is all oily on the inside. The screen, sensor the walls... even the air tubes are oily. So I take a rag, wipe out the air ducts, then (gently) wipe off the MAS and then take some compressed air (45 psi) and blow off the sensor etc.

I hook it back up, drive it around after 10 minutes the hesitation starts to go away. The supercharger kicks off a few times but I have a cure (I have to stop, put the car in neutral, turn it off then back on again to reactivate the supercharger - this is VERY frustrating).

So my questions are:
1) where is the oil coming from? Could it be from the supercharger? Or blow-by oil from the one of the recovery tubes (head, dip stick etc.)?
2) Isn't the MAS suposed to be "dry"?
3) Could oil on the MAS affect the performance, thus telling the system to zag when it should zig all because of the oil?
5) could the supercharger be leaking its oil (thus going bad and needing replacement)?
6) What do I do next?

Shawn

Would you have a K&N filter or somthing similar?

Nope. Standard dealer filter.

Next time you clean the MAS, DO NOT use compressed air.
Best way to clean delicate items like that is to use electrical contact cleaner ( spraycan ).
It will not hurt anything & does evaporate.
Don't know where the oil is coming from, or why your S/C behaves so strange.
I'm a little bit concerned about all your problems, as I also ha a 2000 C 230 K.
Keep us posted.

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2007 C 230 Sport.

Are you getting any more CEL's? I wonder if something is triggering the supe to go into "limp home mode." I wonder what would? Misfire? Changed the plugs, but look at wires? Hhhmm. A puzzle, indeed. Did this begin right after replacing the Air Mass Meter? Perhaps you were not replacing the right part?

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John Shellenberg
1998 C230 "Black Betty" 240K

http://img31.exs.cx/img31/4050/tophat6.gif

Before I purchased the car, I had the luxury of test driving it for two weeks. In that time it only acted up once, but when I had it checked out, no codes were found.

Now three months later, it's the Devil's child (car). Tonight for a bit, it drove great. Went to dinner came out an hour later, it starts all over again!

I'll only get a CE light if I force the car. That is, when it hesitates and wants to bog, I keep my foot on the gas. Not always, but sometimes I will get a flashing CE light, then it will stay steady. I've read the codes and got a P170, P300 & 301. It seems to rotate among them. And after I drive it a bit, the light will go out. (shouldn't it stay on until it is reset??)

The hesitation only occurs when the accelerator is about 1/2 to 2/3 the way down and over 2k rpm's. And you can tell when the supercharger shuts down.

When I changed out the MAS, I soon thereafter changed out the O2 sensor. Again that made no differance. The MAS is the correct one (New Bosch & #'s match per MB). And the only thing the new MAS got me was better starting and idling. Other than that, it is acting up the same, just more often.

My MB mechanic (private small shop) says MB (the dealer) has a nifty computer that you can hook up that tells you everything going on as you drive the car. I may have to surcome to the Dealer . My mechanic is doing some reserch as to other possible solutions since the computer he uses says everything is running correctly (and will note when the supercharger shuts down).

Any other advice about the oil in the MAS and other suggestions always appreciated.
Shawn

Okay, those codes might help. Ant techs might want to wade in right now, as I'm in unfamiliar territory...

You "confirmed" the Air Mass Meter was faulty, through the codes. Did you do this, or did the dealer? Was the replacement confirmed through the adaptation values? I remember Steve once mentioning that a lean AMM can cause misfire codes as well...

Your codes indicate a Fuel Trim Malfunction and Random Misfire as well as Misfire Cylinder One.

I think, and again, techs feel free to jump in, that your misfire condition is causing a "limp" mode of some sort that is shutting the supe down. The supe shutting down is NOT the problem, but a byproduct of what is happening.

The reason you have to shut the car off to reactivate the blower is to hop it out of limp mode. Once the car detects the problem, it trips into limp home again, shutting down the blower.

You'll need to properly diagnose the current problem and sort that out.

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John Shellenberg
1998 C230 "Black Betty" 240K

http://img31.exs.cx/img31/4050/tophat6.gif

Regarding the MAS; I had adaptation fiqures varified at the shop about a week ago. They are right on, so the new MAS is in good shape. I wonder though that the oil on the MAS isn't causing it to act funny?? From what was indicated, a lean reading from the MAS can do this. (?) I think I've read about this before. If so a lean reading under heavy load should cause a shut down correct?

For now I picked up some electrical connection cleaner and will clean off all the oil on the MAS (per manny's advise). Maybe that will give me a clean slate to start from. I'm still baffled as to where that oil is coming from.

Finding out what is shutting down the supercharger and sending it into limp mode is going to send me to my grave! After I do the MAS, it looks like plug wires are the next to go. Should I use dealer or local parts store brand?

Also, what other sensors would cause a "limp mode" situation?

The oil contamination of the MAF sensor is most likely being caused by a crankcase ventilation problem. Your dealer should be able to sort it out. Good luck

I took manny's advice and picked up a can of electrical connection spray from the local auto parts store (I never knew such a product existed). So, I remove the MAS and clean the entire insides out with the cleaner. Again, there was significant oil on the sensors etc. I also wiped out the air tube as far as I could to soak up any residual oil. Reconnected and moved onto my next project - the air intake.

I remove the top cover and noticed the top bottom portrion with visible signs of oil. I proceeded to disassemble the unit and discover that the foam filter meant to trap crank case blow-by (?) was soaked in oil! Almost to the point of dripping. I tried to clean the foam but it just fell apart in my hands (I am assuming that the dealer stocks this replacement). For now I made a make-shift filter until Monday. Reassembled and made a visual inspection of the air intake tube to the supercharger. Oily!!!!!! I wiped what I could until I can take the entire tube out for a proper cleaning.

So from what I can gather; after many miles (I have 98000 mi) the filter became saturated and then passed on the excess it could not handle into the supercharger air-intake, out the other end, through the air ducting making its way to the MAS. (I guess that is possible due to the high volume of air the supercharger is capable of mustering).

I then take it out for a drive - WOW! what a differance! I drove it pretty hard and only once did it kick off the supercharger (I think the rev limiter kicked in). I don't think i'll drive it that hard normally. I'll give it a few days and report back on it's performance.

No one has really said it, but I get the impression that the MAS is VERY sensitive and does not handle contaminats well. Maybe for all those that have a hesitation problem this should be something you look at???

I'll report back in a few days.
Thanks all
Shawn

Shawn

I hope you didn't throw out your old MAS.
Makes me wonder how many of them have been replaced, when a proper cleaning may have been all that was required.
Once you understand how these things work ( measuring resistance ), it is not hard to see why any contamination ( especially oil ), would create problems.
Hope your oilproblem gets sorted out too.
Good luck.

__________________
2007 C 230 Sport.

Well it has been over a week since I took manny's advice and cleaned my MAS. Since then I have had no issues with hesitation or surging. My POWER is back, car runs great - Life is good!

For the many issues that can be classified in the hesitation category, this fix might be often missed (especially since the MAS was brand new and acted up just days after I installed it). But this was just one answer as plugs, wires, coils, fuel filter, rev limiter... and the list goes on, are all "fixes".

I will admit though, I learned a ton about my car by running searches and checking out the oodles of threads. I'll tell you, there are answers out there if you are willing to take the time to read through them.
Thanks everyone!
Shawn

Shawn

Nice to hear that you're running troublefree.
Actually, it's just nice to hear ANYBODY not *****ing about their M-B.

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2007 C 230 Sport.