PretendPilot

So check engine light came on the other day sitting at the stop light right before my road. I get home hook up a Odb2 code reader ( don't have a VCDS yet as first Audi and recently acquired it). Car seems to idle and run fine with no misfires. So I clear the code start the car again everything seems fine. Drive another 750km approx and it in stop and go traffic seems to pop up again while at almost idle, car idles fine drives fine still. Check the code again P0171- reader says: Bank1, micture adpatation (add), Sytem too lean-No signal/communication.

Anyone had this issue or seen it? Only thing I am thinking of is maybe the fuel filter is older and needs replaced?

Is carbon buildup an issue with this model as I see it is with others but mostly TSI, though is this engine a TSI? says nothing on block and can't anything online so is carbon build up just a TSI issue and is that only on the 3.2l version and 3.0t of the a6?

Any advice is appreciated with the limited issue provided until I can get a VCDS.

Thanks.

Unruled

Basically the bank is running lean. It's either got too much air or too little fuel. Possible causes are the fuel pump or filter (but then why just one bank), maybe fouled up injectors or an airleak in the intake system after the MAF. You could test that by spraying brake cleaner or aerosol deodorant around the bank and seeing if the engine reponds to that.

PretendPilot

So looks like it could be a vacuum leak I am thinking.

showing
Bank 1
Short Term FT - 0.8%
Long Term FT - -5.5%

Bank 2
Short Term FT 0.0%
Long Term FT 3.1%


While driving short term bounces around a lot and few pretty low numbers like -8% to -10% when slowing down, which is what I think is causing the CEL light to trip and for it to seem to be randomly happening at different mileage intervals. Anyone had similar issue that they resolved. Been raining non stop last week here so haven't been able to have a good look at vacuum lines.