MAFs

[DJG]

Quite a few people have been reporting their cars being down on performance due to faulty (contaminated?) MAFs. Normally this is only diagnosed after a visit to somewhere like AMD, QST or Star. Certainly I got a blank look when I asked for my MAF to be checked when my car was in for a regular service at my Audi dealer.

From what Dippy and others have written I understand that it is actually quite hard to determine that an MAF is going off even with VAGCOM until it is very sick indeed. How do the specialists diagnose a problem. Do they just try swapping to a known good MAF?

Should we just be treating them as a service replace item. My car has done 60K, so would it be time for a new MAF?

Just wonderinmg if there was a definitive way to see if a new MAF was required.
[img]images/graemlins/beerchug.gif[/img]
David

[fade2grey]

not sure about the S4 but Lancia Evo's & alfa's tend to just get a few blasts of brake cleaner on the hot wire MAF's to clean them first - that normally works.

A

[DavidR]

Both my own S4 and a friends locally had error codes along the lines of R bank lean, L bank lean when accompanied by a broken Air Mass Sensor and lacklustre performance. This was logged on VAG-Com.

[keyser]

actually you have answered your own question. All these issues should be considered.

I remember once a woman came and she wanted to have a chip installed because her Passat 1.8T didn't run well... she said it was to slow.
My friend has dynoed it, and it run 42HP [img]images/graemlins/shocked.gif[/img] [img]images/graemlins/shocked.gif[/img] [img]images/graemlins/shocked.gif[/img]
really

after changing the MAF i dynoed 163HP with stock program.
And after a test drive she said:
NO NO it's too bl..dy fast, I don't want any chip anymore.

[img]images/graemlins/smile.gif[/img] speaking about bad MAFs
LOL

[DJG]

Nice story Keyser
[img]images/graemlins/roflmao.gif[/img]
David

[Dippy]

Yeah - good story.

David,
I'm back up to AmD soon to see how they've done with my car. I specifically asked them to check the MAF. I don't know, but I'd guess that they have a probe that they can put into the air duct to measure air mass flow themselves and compare it with the ECU's reading. Or maybe they just check the fuel mixture (again a sensor at the exhaust I think).

From what I know, major contamination will cause a lean fault code because the ECU thinks there is less air going in than reality. However there has to be a threshold for this detection, below which the car will simply be 'off tune'.

I agree with you that the MAF should probably be replaced regularly anyway. If AmD say mine's OK, then I shall still probably replace it sometime in the future (I've only 33000 miles on the clock).

[SimonS4MTM]

My local dealer reported to me on Wednesday that my MAF was not working correctly.

They can check the readings from it, it is supposed to give 3.0g at idle. Mine was giving 0.1g at idle. I dont know what they mean by "g", gravity maybe?

[smurfbus]

Its grams per second.

[Dippy]

Simon,

was that your original MAF (as far as you know)? How many miles had you done?

[Nige_RS4]

Here is good link (for A4 MAF) on MAF cleaning, which I would recommend you try first if you suspect possible MAF contamination problems.

[SimonS4MTM]

Dippy,

As far as i know it is the original, the car has now done 75k. I have had a K&N fitted for just over a year though, maybe that was to blame. I have now taken it out and put in a standard filter.

[Joshie]

For those wishing to clean the MAF the electrical cleaner (Isopropyl alcohol) is available from Maplins and the Hex bits from Halfords.

[Dippy]

Thanks Simon.

In that case mine gets replaced by 60K regardless.