MAF on its way out or O2?

[ZacharyWS]

So I have been seeing code 17536 for a while now and its time to make the CEL go away.

Background:
1997 Audi A4 18tqm
ko4-015
Unitronic k04 file
VR6 maf housing
USRT 380cc injectors
3 bar FPR
ATP 3" TP
Borla 2.5 stainless exhaust
Forge TIP

at WOT im seeing 150-160 g/s from my maf.
- This is normal? 80% of hp? meaning my k04 is making ~200 hp @ 22psi
at idle I see 2.10 - 2.50 g/s from the MAF
-This is normal? I was told as long as its above 2.00 its ok?
at 032 block i see 10.5% and 25% respectively.
- This is bad. 25% is maxed. Front O2 sensor possibly?

[mike-2ptzero]

Have you logged the 02 sensor readings at wot? If the 02 is going bad the readings should look very lean at WOT.


Where are the specs for the Unitronic K04 file? I only see their stage 1-1+ and the BT files on their web site.

[ZacharyWS]

Before After
0.415 0.685 2000 RPM
0.825 0.835
0 0.01
0.03 0.045
0.835 0.855
0.835 0.855
0.86 0.875
0.83 0.855
0.81 0.835
0.775 0.8
0.78 0.82 6700 RPM

Looks alright right?

[mike-2ptzero]

A little lean, .85 is 12.5:1 on a narrow band.

[ZacharyWS]

So which would you look at first? O2 or MAF?

[mike-2ptzero]

The maf readings look normal for a 3" maf housing. A maf that is going bad will also cause the ecu to run more adv timing, so you might want to check block 022 to see how much timing pull you have. Load readings at the maf would also be much lower then they normally would be.

[ZacharyWS]

0 0 0 0
0 0 0 0
0 0 0 0
0 0 0 0
0 0 0 0
2.2 0 2.2 2.2
1.5 0 2.2 1.5
0.7 0 1.5 0.7
0 0 0.7 0
0 0 0 0
3 0 0 3


thats the timimng retard value in block 020

[mike-2ptzero]

Then its most likey the 02 sensor thats going bad, causing the ecu to keep adding more fuel to get the 02 readings back up.

Have you checked for any exhaust leaks before the 02 sensor? That can also cause the 02 sensor to read leaner and make the ecu add more fuel.

[B5A4Kevin]

mike, I'm going to have to disagree with you, kinda. while the 02 sensor can very likely be faulty, as well as an upstream exhaust leak (seeing as how the turbo has been replaced); I had the exact same fault (bank1 fuel trim multiplicative - system too lean). this was also causing me to get soft limp mode and only boost to 5psi! I would run basic setting 107 (short term fuel trim) and within seconds, my fuel trim would jump up to 25%. my readings for 32 were -1.0 and 25%. I unplugged my maf and it still happened, and all my maf values were fine (03, 115, 211 @ idle). I tried many things including fuel pressure regulator, injector clean, fuel filter, boost/vacuum leaks (even though this would be lean at idle and rich under boost). but then I decided to check 211 under load. there was an up to 70g/s diference between specified and actual values. I swapped in a maf on a known good b6, and the difference went to less than 20g/s. replaced the maf and hadnt had a problem since.

I would suggest logging block 211 while WOT in 2nd/3rd gear. good luck and looking forward to updates. peace.

[mike-2ptzero]

Yes, but your 032 readings showed that the ecu was ok at idle(pulling 1%) and at part throttle needed to add max fuel. His is adding 10% at idle and add max at part throttle. His maf readings are where they should be at WOT for a stock maf in a 3" housing. Those things there are the reason I think its the 02 sensor or a exhaust leak causing the 02 to read lean.

[B5A4Kevin]

ahh. i didnt notice his idle reading was 10%. thanks for the clarification mike. i would still like to see his values for 211 though, just to be sure.

[ZacharyWS]

Ill grab the 211 readings in the morning.

Im positive I have no upstream exhaust leaks as Im anal about replacing hardware and gaskets EVERY time the turbo is removed.

Im ordering an o2 sensor overnight tomorrow. if it doesnt do the trick ill order a maf.

Thanks guys!

[ZacharyWS]

So I ordered a new 02 sensor and put it in, cleared codes and still it jumps up to 25% trim.


Whats next?

[B5A4Kevin]

log 211 at wot in 3rd gear. if the specified and actual g/s vary by more than 20, replace your maf.

[ZacharyWS]

I have no 211 block.

I am on early ecu, mapless. (97 AEB DBC)

[B5A4Kevin]

what are you using to log the blocks. is it base version of vag-com? i believe you can still see 211 on the early models as the block reads load %, g/s specified, and g/s actual, but maybe not available due to specified (speed density using map input). see if you can borrow someones maf, even if not new, it should improve. i put a b6 one in to test mine and the multiplicative lean fault wouldnt come back, and fuel trims were ok. i had that exact fault and full lean off idle and a maf fixed it.

[ZacharyWS]

I put a bran new MAF in it and im still seeing the same results

[kevin12]

I've been having the same code for atleast 6 months, come and go sometimes, but it has been on all the time for awhile now. Finally got around to replacing the front o2 sensor and still got the code coming back.

But I just recently logged block 002 and the maf on the stock tune is only around 113 g/s under WOT in second where it should be around 136 for my 01.

So I figure its the maf but still not 100% sure. Already order a new one and I'm waiting for it to get here soooo we shall see if it fixes my problems like it fixed Kev's. My trims were also around 1.1% and 25%...