EGR Duty Cycle stuck on 99.6 %

[WhiteA6]

Hi all,



I have a 3.0TDi A6 (2010) CDY engine code and am getting pretty low MPG figures. I ran a VCDS log of Group 003 on my last trip to work and noticed that there constantly seems to be around a 200 mg/str difference between the 'actual' and 'specified' MAF values - 'actual' being consistently higher. In addition, the EGR Duty Cycle does not change from 99.6%.


No fault codes showing in VCDS.


Any ideas on other tests I can perform? Thinking something not right with these readings.


Thank you.

[Guest 2]

how "low" is low mpg?

[WhiteA6]

Hi A6_Chris,

I have read quite a few posts about MPG on the 3.0TDi engines and appreciate that I did not pick this engine for economy :-). I seem to get 16-18 MPG on my daily commute - admittedly it is a 7 mile commute and I do sometimes have traffic. Yet, even on longer, clear runs on dual carriage way, I am not seeing above 27 MPG on the average for that drive.

Audi list this engine (2010 model) as 30.4 MPG Urban, Average 39.8 MPG. I dream of getting near those figures....

The car has covered 67K miles, so possibly something needs a clean/replacing.

I unplugged the MAF for a test one night and drove home. This did not seem to alter my MPG figures showing on the dash. Would be grateful of any additional tests/checks people can recommend.

Thanks,

[MarkTM]

Yikes!! I get 26-30 dropping my kids to school an it's less than 1.5 miles round trip on a cold engine

[WhiteA6]

Hi MarkTM, I see you feel my pain

Had a slight development....I played with the VCDS output tests on my engine today - all seemed to do something and I had fun tracing all the buzzing and other noises around the engine bay - and I think it may have slightly freed a sticking component or it may just be a coincidence.

Driving home tonight, I had an average of 24MPG and the EGR valve duty cycle was changing slightly. It went down to about 50% for one reading but most readings were between 80.0 - 99.6%. It seems to keep drifting up to 99.6% and when at this value the 'Actual' and 'Specified' MAF readings start to differ by up to 200 mg/str.

Any ideas?

Thanks,

[gribbo91]

I think my 2.0 has a similar issue. Really low MPG and a slight misfire at idle. Think i might strip down EGR Valve and clean it when I get a bit of free time

[WhiteA6]

Hi all,

I have done a few more logs while driving and have noticed the following:

MVB 10.1 (Actual MAF): From what I can see (courtesy of other posts on here) this should range between 210mg/stroke at idle to greater than 1050mg/stroke at full throttle. I am seeing a lowest value of 250mg/stroke (287 at idle) and a maximum value of 1122mg/stroke, which is within range but seems a little high at idle.

Is anyone able to check if my engine (CDY) has different ranges for this value? Or provide a list of measuring blocks for my engine?

Any other ideas which parameters I should be checking?

I have fitted a new Lambda sensor as some readings from this seemed strange but no change. I have also removed and cleaned the MAF. I was going to remove the throttle body adapter to clean it but was stopped in my tracks as my engine does not have a separate adapter, it is a single cast piece from the throttle body to the intake manifold and I can't work out how to remove it without unbolting fuel lines.

Thanks,