2001 C320 Avantgarde, engine management

[craig.douglas]

Hi All, I'm new to the site and I have a question for all you techno's out there. My wife came home today in a panic, On here way home from work the engine management light came on and the car went into limp home mode. I went out and started it up, sure enough the light is still on but the car is running fine. I took it for a run and all the performance seems to be there. When I got home I popped the bonnet and noticed a small black unit at the front ofthe engine bay was making a ticking noise. I gave it a tap and fiddled with the wire and it stopped ticking. Unfortunatly the management light is still on.
1) can anyone tell me what this unit is, it looks like there are fuel pipes going into it.pump??
2) is there anyway to bring up fault codes on the display, or do you need to plug in diagnostics.
3) Does anyone know what the actual fault might be?

 

[television]

You are a perfect candidate for a new MAF Flilter by the sounds of things.
around £50 from GSF or Bosch.

You can have the codes read with an diagnostic set up.

 

[craig.douglas]

Hi,
thanks for the advice, I'll source a MAF filter tomorrow and let you know how it goes

Cheers

 

[Uncle Benz]

Just as a note, the item in your picture is the fuel tank purge valve. It is normal for this unit to tick from time to time, as it vents pressure from the fuel tank into the engine, rather than letting it vent to the atmosphere. These ultra green times we live in you know.....

 

[type49]

Don't worry about your ticking noise. It's suppose to do that. It will be coming from a valve with "MOT" on it. It vents fuel tank vapour back to the inlet manifold.

 

[type49]

Beaten to it by Uncle

 

[craig.douglas]

Hi all, thanks for the info on the fuel tankpurge valve. Funny noises can be a worry. Malcolm, when you said MAF filter, did you mean the airmass meter, or the air filter itelf. I went to bosch website and it only list an Air mass meter £147 from eurocarsparts.

 

[eric242340]

Hi all, thanks for the info on the fuel tankpurge valve. Funny noises can be a worry. Malcolm, when you said MAF filter, did you mean the airmass meter, or the air filter itelf. I went to bosch website and it only list an Air mass meter £147 from eurocarsparts.

I believe Malcolm was refering to the Air Mass Meter (or MAF sensor as it is also known).

 

[television]

Hi all, thanks for the info on the fuel tankpurge valve. Funny noises can be a worry. Malcolm, when you said MAF filter, did you mean the airmass meter, or the air filter itelf. I went to bosch website and it only list an Air mass meter £147 from eurocarsparts.

You should also ring a Bosch service center ,could be much cheaper. then you fit it into your own plastic housing,you could save£100

Yes as the others said Air Mass meter.

 

[craig.douglas]

Excellent! I'm on the case. Thanks to all who responded. I'll get on to Bosch on monday. I'll keep you all posted

Craig

 

[craig.douglas]

Hi all, a much delayed update: Today I had a very informative conversation with an engineer from Bosch technical sales. I was told by him that Bosch do not sell the air mass sensor on it's own, they only sell it complete with the housing. The reason for this? Well bosch have a range of hundreds of different sensors that are designed specifically for each engine application, so economics prevail and so they only sell them in the housing. When you go to GSF, eurocarparts or your local Bosch agent and ask for an Air Mass Sensor, if they offer you one that doesn't come with the housing then it is NOT GENUINE BOSCH.
OK you say, well the non-bosch units have a "much higher failure rate than the bosch ones" (quote from eurocarparts salesman). Due to the use of older resistor technology the cheaper units are prone to failure caused by engine vibration.
The Bosch units are however sensetive to moisture, both water and oil. If you have water or oil in the line before the sensor it can cause it to fail. When the water hits the sensing head it can cause a sudden temperature change which can crack the resistor,causing it to fail. So if you are changing the sensor it's advised that you check for evidence moisture upstream of the sensor. If there is oil in the duct you need to check the crankcase breather is clean and free from sludge(only if the outlet is upstream of the sensor!)
Hope this information helps you all in making a decision when selecting your sensor

 

[television]

Hi all, a much delayed update: Today I had a very informative conversation with an engineer from Bosch technical sales. I was told by him that Bosch do not sell the air mass sensor on it's own, they only sell it complete with the housing. The reason for this? Well bosch have a range of hundreds of different sensors that are designed specifically for each engine application, so economics prevail and so they only sell them in the housing. When you go to GSF, eurocarparts or your local Bosch agent and ask for an Air Mass Sensor, if they offer you one that doesn't come with the housing then it is NOT GENUINE BOSCH.
OK you say, well the non-bosch units have a "much higher failure rate than the bosch ones" (quote from eurocarparts salesman). Due to the use of older resistor technology the cheaper units are prone to failure caused by engine vibration.
The Bosch units are however sensetive to moisture, both water and oil. If you have water or oil in the line before the sensor it can cause it to fail. When the water hits the sensing head it can cause a sudden temperature change which can crack the resistor,causing it to fail. So if you are changing the sensor it's advised that you check for evidence moisture upstream of the sensor. If there is oil in the duct you need to check the crankcase breather is clean and free from sludge(only if the outlet is upstream of the sensor!)
Hope this information helps you all in making a decision when selecting your sensor

There are 3 types and principles of how these things work, and you can only use the type that was originally used. the sensor type (encapsulated) is used on late cars. I see that Pierburg are also OE to MB

 

[craig.douglas]

Hi Malcolm,
I know I was rambling a little, but the points I was trying to make is that :
1) if your car has a Bosch AMS(Air Mass Sensor) fitted as original equipment then you cannot just buy a genuine bosch sensor, you need to buy it complete with the housing.
2) if you want to buy just the sensor then you need to buy a (non-bosch) pattern make of lesser quality, which may affect engine performance and fail prematurely.

Of course, I am talking about cars fitted with the latest Bosch AMM (Air Mass Meter) units. http://www.boschautoparts.co.uk/pcAirM2.asp?c=2&d=1

 

[television]

Hi Malcolm,
I know I was rambling a little, but the points I was trying to make is that :
1) if your car has a Bosch AMS(Air Mass Sensor) fitted as original equipment then you cannot just buy a genuine bosch sensor, you need to buy it complete with the housing.
2) if you want to buy just the sensor then you need to buy a (non-bosch) pattern make of lesser quality, which may affect engine performance and fail prematurely.

Of course, I am talking about cars fitted with the latest Bosch AMM (Air Mass Meter) units. http://www.boschautoparts.co.uk/pcAirM2.asp?c=2&d=1

Hi Craig, I should have made it clearer and completed my post better, some members who have been to Bosch have said that they can only get the sensor minus the housing, so many of us have been telling people to buy the sensor and fit it into their own housing.

Its very good news with what you say owing to the difficulty of removing the element from the housing. So thank you very much for the info, it all helps to make the forum more accurate.

Bwst regards

 

[craig.douglas]

Hi Malcolm,

Yes, you do have nice valve caps

ATB

Craig

 

[craig.douglas]

Hello again,
the tale of woe continues, after much messing about I have changed the Air Mass Meter. Guess what? My engine management light is still on! Can anyone suggest the next course of action? The car is still running fine, pleanty of power and it idles ok. Is there anything else I can do before I have to put it into a garage for a diagnostics check?

 

[craig.douglas]

Hi Neil,

my cars a petrol so it's possible there is a faulty O2 (llambda)sensor. I'm not sure about the fuel contamination, I live in central scotland and we weren't affected by the recent problems in the south, also I fill my SAAB 95 Aero at the same filling station,usually around the same time as the Merc and it's not suffered and faults.

I was looking at a handheld diagnostics unit:

http://www.gendan.co.uk/product_EZ1500.html

I'm loathed to go to a garage for them to spend 5 mins with something similar and charge £60+vat.

does anyone have experience of these units?

 

[OmniCognateNeutronRangler]

Check with the garage. I have been to 2 now and neither charged to plug the star thingy in and give me the results. One main dealer and one MB authorised service centre.

btw, is the 320 a v6? If so you will have 4 sensors. Unfortunately they are £140 each.

 

[television]

Hello again,
the tale of woe continues, after much messing about I have changed the Air Mass Meter. Guess what? My engine management light is still on! Can anyone suggest the next course of action? The car is still running fine, pleanty of power and it idles ok. Is there anything else I can do before I have to put it into a garage for a diagnostics check?

When the MAF goes down,other components deviate from their stored settings to try and compensate, it could have just got latched up as some of these things do, and as it is running fine it may go away on its own or maybe it just wants clearing.

This was the way that Omni's car went when he got bad fuel. the lamp went out on its own accord

 

[OmniCognateNeutronRangler]

as Malcolm says, my warning light went out after about 120 miles and none of the fault codes came back after I had them cleared. Sadly I still had the work done as TEsco were paying and I've had trouble ever since, but that's another story