jeffkruse

I am getting these DTC's and want to check to see if my MAF sensor is bad. I have a VAGCOM and heard you can do something with the Measuring Blocks to test the MAF. I have researched here and the web and cannot find anything for 4.2L. I must not be entering information correctly because I get different engine sizes but not 4.2L. I have cleaned my MAF sensor with CRC MAF Sensor spray but codes keep coming back. Any help would be appreciated.

17538 - Fuel Trim; Bank 2 (Mult)
P1130 - 001 - System too Lean
17536 - Fuel Trim; Bank 1 (Mult)
P1128 - 001 - System too Lean

MP4.2+6.0

Instrument with VCDS. Go for a test drive while recording data, including RPM and MAF flow rate (in grams/sec.). As it nears shift points (high RPM), you are looking for a peak flow of at least 80% of rated HP measured in g/s. Thus on my 2000 C5 4.2 w/ 300HP, I was looking for at lat 240g/s for example.

1-2 shift and RPM change is fast; easiest to see near 2-3 point. Do not try to read it yourself while driving; either use the recorded mode or bring along a co pilot to read and watch the laptop.

jeffkruse

OK, I was not sure what group. So I did 001,002,003 Because I logged it there were alot of lines in excel. I only copied the two highest RPM and G/S. I am not even sure I did this correct. The results below. Advise

Group B: '002

Engine Speed(G28) Engine Load Injection Timing Mass Air FlowSensor (G70)
3320 64.7 14.35 96.31
3200 67.7 13.12 100.5

MP4.2+6.0

You need data up near redline where the peak flows will be. This is only data at 32-3300 rpm. If you instrument it and then download the spreadsheet type stuff, find the lines up around 6000 rpm. And again, if not clear, you need to go out and punch it under hard acceleration through the first couple of gears, and you need the throttle wide open/to the floor.

jeffkruse

OK here are the (I think) the correct results. I thought I got it to 7000RPM but did not

Group B: '002

Engine Speed(G28) Engine Load Injection Timing Mass Air FlowSensor (G70)
6040 68.4 11.48 184.25
6480 64.7 11.07 186.69
6000 66.9 13.12 182.11

MP4.2+6.0

So, you are way off on the expected reading. You can fill in the HP rating of your particular motor, but meantime 186.69/.8 = 233 predicted HP. Not even close. On my 300HP 2000 A6 4.2 with a bad MAF, I pulled slightly over 200 g/s, and of course even that was low for a lower output version. Post MAF change I got up to around 255 g/s as I recall, so it did also validate the rule of thumb for me post-change. My only doubt here is why the load is only showing at about ⅔ on yours. You might also do a run to include throttle position, and make sure that specific element is showing >90% at least. On my A6 it was de tuned relative to D2 A8 and i always suspected it was at the throttle position or body size/diameter; mine would show up to around 95% on throttle position peak.

nathanwind

I did a different version of the MAF test (essentially running it unplugged to see if the same codes popped up) as someone describes here:
https://www.audiworld.com/forums/a8-...2878901/page3/

It's also worth noting that there seems to be a rash of "lean" codes with folks lately (myself included as I started the above thread). For me, running a bottle of BG 44K through a tank of gas took care of my lean codes...and similar actions seem to have been taken by a few others recently (in similar threads). Anyhow, it may be worth $25 and a tank of gas to see if it helps.

However, I do realize your above test shows some MAF issues so that could likely be the culprit.

jeffkruse

I purchased one from here. comes with a 5 year warranty, I know is it not a bosch but for the price I thought I would try it

http://www.autopartswarehouse.com/sk...gs+Best+Seller

jeffkruse

Ok I got the part in the mail and installed. It did not even register on my VAGCOM. Got a DTC stating "16486 - Mass Air Flow Sensor (G70) P0102 - 002 - Signal too Low - MIL ON". Instead of ordering another one, does anyone have a suggestion what brand I can get that will register and not break my bank account? Thanks

dvs_dave

You already answered your own question....buy a Bosch one before you waste any more time and money on cheap junk parts.

Hardly an expensive part at $150 in the realm of Audi A8 parts.
http://www.ecstuning.com/Audi-D3_A8-Quattro-4.2/ES514002/