Air Mass Meter

[Dunx]

Just had my E300TD in for some work at an indie and apparently I need a new Air Mass Meter (after reading DTC's). I'm not entirely convinced as I'm not experiencing any idling issues or lack of power. I had asked them too investigate my starting problems when the car is left overnight with the nose higher than the rear end. I had thought this was air in the fuel system and had replaced all the clear fuel lines and o-rings around the fuel filter area, but the problem is still there, especially so on really cold mornings.

Could this be the cause of my starting problems? What are other folks' experiences with MAF problems?

Is it worth buying one form the US as a new MAF is around £200 + VAT here and around $150 plus shipping over there?

Any thoughts on this would be greatly appreciated.

Duncan

 

[jberks]

My experience is that MAF's tend to trip the get you home mode. As you haven't had this, I'm surprised that its been diagnosed. However, if it's reading out of spec so the O2 sensor is complaining its runniing rich then it could be on the way out I guess. Certainly, being solid state, it has no relevance to inclined starting issues. I can't see why a US would be any different to a UK one, though I would be careful with part numbers but you can also get reconned ones which may be worth investigating.

 

[johnmc]

Hi Duncan,
I had a starting problem on my petrol car caused by the air mass meter. The car wouldn't start when "partially warmed up", like when left for 10mins after a good run or stopped and re-started while not fully warmed up. So, it could be causing your problem. Got mine fixed on warranty, garage wanted 400quid otherwise!

John

 

[television]

I did put up a posting some time ago of the dangers of miss reading fault codes, A fault somewhere on the engine will often say MAF faulty,
What happens is that other parts of the engine try and compensate to keep the engine running. these components have deviated from their stored memory value, so you do a reading of codes and up comes MAF.

The MAF could not care less about facing uphill/downhil.

There must still be air from somewhere,maybe from the cold starting device

Just for the record from the States say $180 with postage =£100 max.

Also for the record A company "Standard motor Products" has launched a new range of MAF 's these low cost units are supplied without the plastic housing as this part does not fail 300 cars listed, not yet for our's but it will come.


Malcolm

 

[Dunx]

Not so sure!

Thanks for the replies guys. I just did a quick test to see what would happen. I disconnected the MAF (removed the plug and taped it up) and took the car for a spin. Engine was a little smoother and sounded a little better, but the car did not accelerate as hard and was not as keen to kick-down as it does with the MAF connected.

After the plug was reconnected, acceleration was back to normal, as was kick down.

I'm thinking the MAF is is still servicable. Any thoughts?

TIA

Duncan

 

[big x]

Just for the record from the States say $180 with postage =£100 max.



Malcolm

No it doesn't it's alot more,plus you may get hit by VAT and import tax on items over £14 in value.
If you go to a Bosch distributor here you can just buy the insert sensor far cheaper.
These are also cheaper through MB van outlets if you can find the Vito van MB part number.

adam

 

[jberks]

Thanks for the replies guys. I just did a quick test to see what would happen. I disconnected the MAF (removed the plug and taped it up) and took the car for a spin. Engine was a little smoother and sounded a little better, but the car did not accelerate as hard and was not as keen to kick-down as it does with the MAF connected.

After the plug was reconnected, acceleration was back to normal, as was kick down.

I'm thinking the MAF is is still servicable. Any thoughts?

TIA

Duncan

Doesn't prove much unfortunately. It may well still be working, but it may not be putting out the right data, so its better with than without, but not right in either case. Alternatively it could be fine!
What happens if parked differently. If its consistently ok, I'd be looking elsewhere. As above, the MAF doesn't care where it's pointing.

 

[Dunx]

Originally posted by big x in another thread
Details on how MAF's work can be read here,note what they say about oiled sport filters
http://www.x-desk.net/ximages/21302_pgsi0079en.pdf

I tested the voltages as outlined in the doc above from another thread posted by big x. Although this is not for my MAF (mine is made by bosch and has a different MB part number) the process should be the same. I get 12v across pin 2 & earth and 5v across pins 4 & 3. With the engine off, I get 1.09v across pins 3 & 5 (outside the spec of the model documented). With the engine running I get between 1.5v at idle & 2.5v at around 4000 rpm (was too scared to go any higher under no-load conditions!) across pins 3 & 5.

My question is does this look as though the MAF is functioning correctly, given that a Diesel does not rev as high as a petrol engine? Or should the MAF reach the top voltage (3.8v-4.4v) at a lower engine speed?

Any thoughts would be appreciated.

Duncan

 

[big x]

I tested the voltages as outlined in the doc above from another thread posted by big x. Although this is not for my MAF (mine is made by bosch and has a different MB part number) the process should be the same. I get 12v across pin 2 & earth and 5v across pins 4 & 3. With the engine off, I get 1.09v across pins 3 & 5 (outside the spec of the model documented). With the engine running I get between 1.5v at idle & 2.5v at around 4000 rpm (was too scared to go any higher under no-load conditions!) across pins 3 & 5.

My question is does this look as though the MAF is functioning correctly, given that a Diesel does not rev as high as a petrol engine? Or should the MAF reach the top voltage (3.8v-4.4v) at a lower engine speed?

Any thoughts would be appreciated.

Duncan

Duncan there was a thread about this over on http://www.mbclub.co.uk
Dieselman has the answers if you ask there.

adam

 

[Dunx]

Originally posted by big x
Duncan there was a thread about this over on http://www.mbclub.co.uk

Thanks Adam. I found the info on the mbclub forum. Looks like my MAF voltages are reading low.