When to replace MAFs?

[paul_23]

Seems that MAFs are a common issue on RS6 that need to be replaced fairly often but they rarely fail, just underperform. How do you know when they need replacing without a dyno test. I have VAGCOM.

I have no fault codes, it runs ok and pulls well but logging block 2 in vagcom shows fairly big differences between each MAF: at idle or low load one is sometimes 100% different, as load increases the difference reduces till full boost at say 5000rpm is about 10% difference.

I have spoken to the Audi dealer here (Dubai) and the service advisor couldn't even bluff convincingly. I dont really want to book it in to them for them to bluff their way through the diagnosis and charge me a mint for it unless I know there is a problem worth dealing with. No independents I trust either with something like this so not much choice.

Thanks in advance

[ecain63]

Many owners here change them at every service. or every 10k in mileage speak. They are pretty inexpensive in RS6 terms and are the main cause of power loss (other than blown ic hoses).

[MoRS6+]

Many owners here change them at every service. or every 10k in mileage speak. They are pretty inexpensive in RS6 terms and are the main cause of power loss (other than blown ic hoses).

Hmm, might get Doug to change mine at the 30k service. How much are they again?

[paul_23]

I didn't realise they are changed that often.

Here they cost just over 100 quid each and I guess a couple of hours to fit them??

Can they be fitted as a DIY job?

[ecain63]

Its not stated in the service sched to change them as often as every 10k.........but! Due the mafs and N75 being so delicate and temperamental it pays to change them regularly. With you being in Dubai i'd suggest that the MAF's would get clogged up quicker than they do here due to the dust. 100 quid is expensive, but its only a half hour or so job as they are just down behind the airbox, along with the n75 so might aswell do that too. DIY is doable if you know what you are doing, but make sure that when you expose the inlets at the back of the engine you cover them or bung them with a cloth cos if you get ANYTHING (airbox screws, sand, contact lense lol) in there then it'll be a full rebuild and big money bill.

[el_ringo]

I would say every 10k is overkill. I had my ones replaced with the N75 at DVs when I had the map done.

I would think an interval of 2 years / 30k would be sensible a good minimum.

R

[ecain63]

With some owners MAF's lasting only weeks / months at times and others never needing replaced (kinda like DRC and TC's - is it an RS6 thing?), it really is up to the individual. Like i said, there are owners on here who regularly change their N75 and MAF's, but at the same time there are some here who have probably never changed them and will never need to. The best way to test if they need changing is to have the car rolling roaded with the old MAF's and N75, and then get it roaded again with new ones. Sometimes it can be worth as much as 50 - 100 bhp. Often the loss of power is gradual, over a period of months, so you might never realise you have an issue as the car will still feel pretty quick.

Didnt Condor24's car find its missing 50 or so BHP with the fitting of new MAF's last year (and then another 50 when he realised that the ecu had been changed from an MTM Stage1 to a standard map without him knowing about it)?

Each to thier own but worth a look anyhow.

[Shoppinit]

Don't the lambda sensors correct for the MAF variation?

[RS6-4dr911]

You guys have me thinking I'm overdue. Still on originals at 45k miles and wondering why 0-60 times are off by roughly a second from typical. Logging showed mostly a 10% variance but, as above, some spikes that were a lot more than that. N75 activity appeared normal but as many people seem to have problems disappear with a new one, I'm tempted to try. If I find lost HP by doing the above, I'll be sure to post the results for future reference.

[paul_23]

It would be useful if someone could log block 2 and dyno run with old MAFs, and then do same with new so we have a comparison.

I will get mine changed in a few weeks so will have block 2 logged before and after so can post it. Have no dyno results....

I had my N75 changed recently so no need to do that.

I see some change the diverter valves regularly too but how do you know if they need replacing? (off main subject but relevant).

[ecain63]

No need to change the DV's more than once. The problem is that the standard DV's are plastic and become brittle with heat from the engine. A popular option is to go for Forge metal DV's. They are not overly expensive and only need light maintenance (quick check / lube at service intervals) to keep them 100% sound and in working order. They look good too, coming in at least 2 colours (black and silver - and maybe blue but cant find them).

http://www.forgemotorsport.co.uk/conten ... t=FMCL007P

[jd_hants]

I have no idea whether mine have ever been changed or the DVs, N75 etc etc etc.

The previous owner had it serviced at Northampton Audi. Anyone know whether the list of work done is generally made available to new owners? Can other Audi dealerships gain access to this info?

[jd_hants]

p.s. I changed a MAF on an A4 a while ago. Someone told me you have to tell the ECU that a new one has been fitted / reset the ECU because it compensates for degradation?? Or is this a load of tosh? It seemed to cure the problem anyway so I never persued it.

[ecain63]

Never hurts to do an ecu reset. Just unplug the battery for 90 seconds and delete all resulting codes with VAGCOM.

[tartan_rob]

For reference, I did have a MAF die. Dead. MRC confirmed it does happen from time to time.