Supercharger problem please help!

[scubad]

Supercharger problem, advice sought

Hi, I'm new to this site, I joined to see if anyone can offer me some advice.
I have an X reg C220K Estate which has developed a problem. A few weeks ago it started to lose power, the gear changes got very slow and the egine would rev between changes, then the ECU light came on so I took it to my local independent. They said that there were actually 4 faults stored in the ECU, 1 supercharger, 2 lambda sensor and something else I can't remember.
They cleared them and told me to drive the car until the light came on again (no charge!), the car actually ran the best it ever has for a week or so but then it began to feel a bit wrong, then it was back to the way it had been and the light came back on.
Anyhow, the fault reading was 'supercharger flap, secondary air mass too low'.
From what I have read so far it appears that this could be either the ECU or the supercharger. Is it worth buying second-hand parts, as I don't think I can afford either new?! D

 

[brandwooddixon]

Wlecome to the forums.

Just posting to let you know that you've not been forgotten.

The problem may not actually be mechanical. From reading these forums it's plainly clear that quite a few "mechanical" fault codes are caused by electrical components, sometimes totally unrelated to the fault shown. This is because the original programmers sometimes have to try and determine faults from quite esoteric sources.

It's interesting to note that a loss of power, followed by slow gear changes show up before the supercharger faults appear.

As an aid to those more knowledgeable than I if yo could post up the first 6 digits of your VIN and if possible the actual fault codes retrieved by your independent (only becuase they sometimes change to mean different things).

Just noted that you mentioned a fault of "secondary air mass too low". I wasn't aware that supercharged cars had a second MAF sensor, but if they have then this could be due to oil contamination of it causing a fault. There was a recent post regarding breather pipe blockages on Kompressor vehicles causing this.

 

[type49]

As above, bit more info on the car especially as they don't make a C220K! Also X reg is the change-over from one shape to another so first 6 numbers please (IE. 203245). "Secondary air" refers to part of the breathing system, so yes, it could be blocked as suggested. Also, it could just be a blocked "flame trap valve" - nice & cheap to buy but it's fitted at the back of the head area & even with the correct 90-degree open ended spanner needed to undo it, it's a bit of a pig to do. No more than an hour at the dealer though.

 

[scubad]

Hi guys, thanks for the feedback. Sorry, it's a C200K, don't know why I put 220! It's Tiptronic, but I think it's the model before they changed the body shape slightly and the first number on the plate under the bonnet is 0904610 3. Is this the VIN?
Just going on gut feeling it seems more like a breather or something by the way it comes on gradually and the severity of the problem seems to fluctuate slightly, it's not just 'on or off' as I would have expected with an electrical fault. Admittedly cars like this are way beyond my knowledge of auto mechanics!
Cheers D

 

[jimsinessex]

I think the reference to an "air flap" fault may refer to the modulating flap valve (MB call it a recirc v/v on parts diagrams) between air filter and kompressor outlet. I am assuming your model does not have a clutch operated kompressor. In which case the flap will start in the fully open position and close in as kompressor output rises. As revs rise it will modulate to maintain the required kompressor output pressure for the load demanded. If it is remaining open because it is stuck or receiving no signal the kompressor flow will be recirculating back to the inlet and power output will be low. Your problem does not sound like a faulty supercharger but more like a fault with the flap v/v or control signal.

Jim

 

[brandwooddixon]

The VIN should be visible on a little plate through the windscreen on the passenger side. It normally starts with a W. The number that you gave seems more like an engine number.

 

[scubad]

Hi, have been offline for a while due to Broadband problems! Car is old shape but new engine if that makes sense. Took her to Bursledon Motors in Durley, Hants - highly recommended. They connected her to Star Diagnostics and the problem is the Recirc air valve/flap. He used the machine to reprogram the valve/ECU and it's been fine ever since, though will cost me about £400 if it goes down again, so fingers crossed! Thanks to all of you have tried to help, and have a happy and healthy 2008! Dave

 

[jimsinessex]

Thanks for posting back, glad you got it sorted.

The info that the recirc flap can be reprogrammed is useful as many less knowledgable dealers would no doubt be fitting a new flap valve straight off at our expense.

The £400 you quote as the cost for "next time" sounds very like a new recirc valve + fitting. Be very sure that they check there is a signal from the ECU to the valve before condemning the valve as it may well be the ECU playing up and the valve is ok.

Jim