W124W203

Is there anybody who can come up with an answer to this problem please. It started about two years ago exhaust manifold cracked then the mil light came on put on code reader & came up with replace the 2nd lamba sensor. So I had the manifold welded up & replaced the lamber sensor (genuine) & had the MIL light cleared fine for a few weeks then one cold night the MIL light came on. Put on Bosch Code reader came up with MAS sensor replace, did that with a seimans Sensor with the merc logo etched off NOT a cheap one, Seimans supply MERC with them in fact the original one was a seimans with the triangle on. Ran fine for a month ish & guess what same thing again when it was a frosty night. Got it changed under warranty ran fine all summer at least 9 months . Then one cold night (winters here again) it happened again managed to get it exchanged for a new one again under warranty but told not to go back again. Cleared MIL light again. Ok a for a while but yet another cold night it came on again. Every time the light comes on it is very sluggish for about 4 or 5 days then it clears itself and runs great (Quick acceleration) etc. When ever its below about 4 degrees centigrade the fault appears more often than not. The last time it happened was FEB this year ran sluggish for a few days then cleared itself . I have not bothered clearing Mil light yet and it is running great. It only does it in the winter months. Would love to find out what is causing this. Any help appreciated. MY car is a C200K saloon 1998cc 2001 model. Sorry for such a long thread.

ohlord

codes were you pulling?
Slow to heat o2 sensors after chilly nights can throw a fuel trim code on both banks of cylinders.Another culprit is a fouled fuel filter,have you changed yours?
Clean the maf with crc brand maf cleaner,see if that helps.
ohlord
"GOT CODES?"
You are not the only member suffering from these symptoms.One contention is that during the winter they blend the fuel with more Oxygenated ethanol.I do know that here in Washington state if I fuel up with Arco gas in the winter my maf starts the intermittent p0170 and p0173 codes.Arco is 10% ethanol blend.

Buellwinkle

Did the MAF come from ebay per chance? Many people have had problems with aftermarket MAF's. Make sure it comes from a dealer and it's in a blue box. Also, did you actually get a MAF code or a fuel trim code? If it's an actual MAF code it could be the connector the MAF or just a non-MB MAF.

W124W203

Hi folks thanks for your input every bit of help is appreciated Buellwinkle here in the UK there is Indi called Europarts which is probably the biggest of its type in this country where the Maf sensors came from.They were in a Siemens boxes which 1 is in front of me now (thats why I have spelt siemens right) Also the box was sealed when given to me it also has a hologram on it so I would say it was genuine. Why would the MIL light come on if it was a non MB part, only in the winter? As for the codes all my Bosch man tells me is replace the air mas sensor, next time i will have to make sure he gives me the codes. Another ideas appreciated.

Buellwinkle

The specific code helps. For example, many people replace or clean the MAF when they get a P017x code for a fuel trim error but sometimes that can also be a vacuum leak. Now a real MAF malfunction is a P0100-104 but I have rarely seen those on the forum but that would actually mean your MAF is dead or seriously injured.

The way a MAF works is there's a wire that's heated at the tip of the MAF insert. As air moves over the heated wire it cools the wire. This is how the MAF measures air flow. You have the M111 motor but I'm not sure if your's is a Kompressor model or not. In the Kompressor model (the only kind sold the U.S.) the MAF is after the "Kompressor" so cold air would never get to it as it's heated by the compression. If it's a normally aspirated engine, it would have to get pretty cold for the MAF to not operate correctly and there are plenty of cold places in the U.S. and I've never heard of anyone on the forums having temperature related problems with their MAF. I guess it could be possible that when it's very cold, moisture forms on the MAF wire causing a problem.

As for bad MAF's, in the U.S., the M111 motor uses a Bosch MAF from the factory but there are Siemens units in the aftermarket. Do you still have the original? If you do, you may want to clean it with MAF sensor cleaner and see if that works better for you.

W124W203

Hello Buellwinkle in the UK “K” stands for Kompressor so yes mine is one, also the original MAF sensor which I still have is a siemens unit with the Merc emblem on ( it is a five wire MAF sensor) if that helps. In the past I put the original MAF back on and it ran fine until the temperature dropped below about 4° centigrade then the MIL light would come on and most times the car would be start to run sluggish for a few days. Your thoughts on a vacuum leak sounds possible because in winter when cold plastic / rubber become hard and with the engine is running could cause a leak (vibration), what do you think. There is a breather pipe which connects to the rocker cover and goes to somewhere near the Kompressor that has gone quite hard and there was has a damp patch of oil buy the connector at the rocker cover so I used a cable tie to seal it off do you think that is a possibility? You mention moisture that also sounds possible because her in doors says that it seems to be more cold and wet when it happens, but how do I overcome that? But on reflection it was ok for a few years before. Your thought please.

W124W203

Ohlord I have been thinking about what you said about the o2 sensors being slow to heat up then giving a fuel trim code does this mean the code, replace Mas sensor will come up? Just in case it makes a difference my C200K is a straight 4 petrol. And I have fitted a new fuel filter. With thanks.

W124W203

Hi folks I have got round to having the MIL cleared but not on a Star machine my garage has a Bosch K 750 code reader (I think its called). The code the Bosch machine gave was “54” , and the description was quote :- AIR MASS LOW. Can anyone interpret this for me please. With thanks.