DTC's 17536 and 17538 - system too lean - new MAF?

[Golfather]

Wonder if any of you guys have come across these two faults?

System too lean on bank 1 and bank 2.

I got a suggestion on AudiWorld that I should change the MAF.
Before I shell out for a new MAF, does anyone know if theres anything else that I can check to solve these errors?

Also, is it possible to upgrade to an RS4 MAF, and any benefits in doing this to an otherwise standard S4?

Many thanks.

[sitas3]

I'd love to say 'Give your Audi dealer a call' but they'd not have a clue! try and give a specialist like Kim Collins at QST or AMD a call to see what they say. It could also be caused by an air leak in the vacuum system somewhere. QST have a vacuum pressure tester exactly for this purpose.

I think that in order to have the RS4 MAF unit on the S4, you'd have to change the airbox and Y pipe also as it is wider - probably a bit more to do than that!

please let us know how you get on.

[toasty]

i had the exact same problem on my S4, the dealer changed the MAF and that fixed it first time. I think they are about 100quid. I did try cleaning it first etc... but no joy.

[smurfbus]

remove the connector first. now your ecu will be running on rpm's. It will not give the low rpms push but it wont get too lean either. Some peeps swear it's faster that way at quater too?

[Dippy]

To get lean from a faulty MAF it must read lower than actual airflow. This is indeed the preferred failure mode due to contamination.

You can check the airflow reading using VAG-COM - there is advice on what to expect elsewhere here: try a search on MAF or g/s.

You will have no advantage from an RS4 MAF unless you have increased the maximum airflow beyond the S4 MAF's capability, and generally this means K04s plus other mods. However there is anecdotal evidence that the newer Hitachi MAF has higher reliability than the Bosch one (which I assume you have). There was another post about this recently - check the S4 forum.

[Golfather]

Thanks guys, some very useful info.
I think its definately the MAF now as I cleaned it (or attempted to) and now its knackered completely!
"Low Signal from MAF"
Funnily enough though, without the MAF working (or disconnected), the car doesnt go into limp mode
and pushes out full boost, although I've lost a lot of torque at early revs.

Audi charge 190+VAT for this unit, Bosch direct charge 212+VAT just for the sensor or 60 quid exchange, and I can't use the later Hitachi one as the electrical connector is different.

However, I may have found an alternative supplier, will keep you informed.

[KayGee]

www.ecstuning.com

about 130 inc shipping to the UK. Also try VAGparts they always seem very competitive.

[Dippy]

Funnily enough though, without the MAF working (or disconnected), the car doesnt go into limp mode
and pushes out full boost, although I've lost a lot of torque at early revs.

I am a little surprised, because I had a case of limp mode 2 years back just because one of my sensors said the cats weren't up to temperature, so emissions might be too high.

However maybe Audi have programmed the ECU to ensure that without a MAF connected, the engine still runs with confidently low emissions. I guess this means that it must run the lean side of normal. If this is true then you still don't want to run without a MAF for very long because the turbos might get a bit hot.

[Golfather]

Cheers Dippy.
Yep I havent used the car at all since the MAF went faulty, as I didn't want to cause further damage.
Just waiting for an exchange unit from Audi @ 70 quid, which should see my power back, and hopefully
rid those two pesky lean codes.

[Golfather]

Picked up my MAF yesterday from Audi - 80 quid exhange.
Installed it, cleared the codes and voila - perfect !
No codes have returned, the MAF is giving out healthy readings, and the car is pulling like its just been chipped !

Thanks guys for all the help.