RS6 Owners with Vag-Com I need your help

[42TT]

Fellow RS6 Owners,

For the last couple of weeks I have been trying to diagnose a fault with my car. The fault is a variance of the Mass Air Flow Sensors.

They should always be almost identical to each other but on my car the variance can be anywhere between 6% and 40%.

I am asking for people who have vag-com and an RS6 if they could in their spare time do a log of the afm's. The log would need to consist of the following:


Run car until up to operating temp.
Connect Vag-com and log Measuring Block 002
Allow car to idle for a minute or two then,
Rev the car til around 4000rpm and back to idle a few times.If there is anyone willing to a datalog while driving that would be fanatastic. You would need to be on a wide open road and log the car in 3rd in tip mode at Full Throttle without engagging the kickdown until redline.

I greatly appreciate anyone help in trying to sort this problem out as I am sure there are more than just mine with this problem (maybe not to my extent) and it couldnt be helping the performance of our RS6's.

This is a link to the thread where other great people such as SKIWI, OCT USA, FUngusmud and many others have tried to help solve this problem.

Thread Link: http://www.rs6.com/forum/showthread.php?t=11983

Best to load your log files on here for future reference to others.

Thanks for your time and help in advance

42TT

[O.CT USA]

I will try to log block 002 when possible.

[42TT]

O.CT USA- Once again thankyou very much.

After looking at ELSAWIN i discovered that the MAF's at idle should be identical or very close to it. The variance of 20% from what i understood is during a test to make sure the turbos are working uniformally so i take that the near identical MAF readings should stay the same through the rev range assuming the turbos are working perfectly.

I have attached two excerts from ELSAWIN showing what I mean and sorry for the poor quality the site only allows small images files

Thanks
42TT

[Hy Octane]

MAF's are finiky things.. why not just replace both and start from scratch.. When in doubt, yank it out!

[42TT]

I have tried a spare pair that I have and also swapped from Bank1 to Bank2. Believe me I would be happy to pay for a new pair of MAF's if i knew it would fix the porblem :(

I have attached the latest logs for reference to those who are kind enough to go out of their way and do the data logging

Thanks
42TT

[42TT]

Anyone?

So no one out there is looking for an excuse to drive their car at WOT in 3rd gear and possibly gain some HP in the process if they find there car isnt running at 100% of its potential?

42TT

[ruxprncd]

Greetings - I will in the next few days. What kind of a file is the MAF readings attachment you posted? I tried .jpg but no worky.

[42TT]

RUXPRNCD - You will need to rename the file to .xls and view in using Excel. I appreciate taking your time to view the post and log your car

Regards,
42TT

[skiwi]

i have already stated my results ~5% variance @idle.

also, you will find wide variances when doing wot runs due to the sampling rate - vag-com samples serially so when under acceleration, the results will almost never be in synch.

to identify the issue, you need to be at a constant engine speed - for leaks, this is best @idle.

[42TT]

SKIWI- Can you define your 5% variance?

[skiwi]

yes: one maf was measuring within 6% (just rechecked) of the other one at all times. the readings were not consistent in the sense that either maf would vary realitive to the other. in other words either maf would vary high relatoiive to the other.

the majority of the time the variance was less. the average variance was 2.4%, standard deviation 1.9%

[42TT]

Skiwi - Much appreciated so mine still seem to be out by too much. Other than a vaccum leak what else could it be?

Thanks
42TT

[skiwi]

for the variance @idle, it would only be leaks, restrictions or maf's - can't think of anything else. you have checked crankcrase breather?

[42TT]

By crankcase breather I assume you mean the PCV valve system. I plan on removing all pipes etc and blocking off the lines and see if that fixes the problem. If it does then work backwards to find the leak.

[peiserg]

why not just take it in to audi? or is ther an issue with competence?

[42TT]

peiserg - I am in Australia only 30 RS6's here and little to no training. they wanted the car for a week to diagnose why it always went into limp mode and it took me 1/2 a day to figure it was the alternator overcharging doubt il trust them with this

[42TT]

Here is a lot from GardinerG from rs246.com apart from the variance at idle not much difference really unless I am missing something

42TT