Air flow sensor

[Locky]

Hi all ... after reading all the posts about air flow sensors becoming dirty and causing all sorts of problems I thought I would take a look at mine. Thing is mine didn't look anything like what has been described on here. I thought it was a wire... but mine was a finned heatsink on one side then like a small resin pip in the inside. Is this because mine is a cdi or is it just a later version air flow sensor?
I just gave it a blast of compresed air and re-installed it.

 

[jberks]

I believe there are various designs, but a word of caution. Dirt is one way they can die, but component failure is equally as common. As far as the dirt is concerned, Under normal circumstances, it is protected by the air filter, whereas when removed, it is open to the elements and bits of dirt in the air, pollen etc can get to it. In the case of MBs I suspect that on the younger ones (like mine) the failure was due to poor quality components and on the older ones, poor maintenance at some point (unchanged air filter etc). E.g. We have a 10 year old C220 running fine with the original sensor, but then the maintenance since new has been meticulous. Same maintenance care on my E240 got me 4 1/2 years and I needed a replacement. Its just the luck of the draw.

 

[philharve]

Hi jberks

When the MAS fails, can the car still be driven or is performance so severely impaired that replacement cannot be avoided and a repair must be undertaken before the car is driven again?

Are different types of MASs interchaneable or must a faulty MAS be replaced with a new one of the exact same design?

Is recalibration required when a new MAS is fitted?

REGARDS Phil

 

[jberks]

Hi Phil,
I have heard of people complaining that their MAS is on the way out, though in my case it failed totally and instantly. One minute all was well and the next it crawled. I had some very slight hesitation for a few weeks earlier which was probably related, but this showed up as an O2 sensor on the diagnostic and the MAS packed up in the 3 days I was waiting for the sensor to come in.

Basically, as I understand it, the problem is that it can play up and give incorrect info to the ECU, but so long as the response is within allowed parameters, the ECU will believe it and behave accordingly. So, if the ECU says the air is dense, the ECU will enrichen the mixture. This will in turn potentially damage the O2 sensor and the cat (possibly what happened in my case). Alternatively, it may go the other way in which case, it will feel a little short of power. Or, as finally happened to me, it may put out way off data in which case the ECU will stop believing anything, drop into 'get you home' mode and it will run like a Trabant (though it will get you home!).

As far as I am aware, so long as it was ok, a used one would be fine, though it would need to be identical to the original as it must match on both the data side and clearly it must fit the air intake pipe perfectly too. I am not sure about calibration, I have heard mixed comments on the subject. I can't see why you would need to calibrate from a technical perspective as presumably they should all behave identically. I believe the MAF has to be factory calibrated.

There is an interesting doc on Porsche ones, and the Merc one is pretty much the same in principle. Have a look at this link.
http://www.jdsporsche.com/faq.html

cheers,
Julian

 

[pascal]

That article sure is interesting JB.

It's a pity it not directly related to MBs + Photos.
But having said that, it explains very simply what MAFsensors are all about.

Pascal.