ajg617

So I'm trying to understand why my '03 Avant with the 3.0 and fly-by-wire accelerator engine surges under certain low RPM conditions. If in neutral/park, I depress the accelerator a small amount (say bring it up to 1K), the engine will surge 250 rpms continuously between 750 and 1000. Maybe I am making a false assumption, but I'm assuming that the fuel supply is varying. If I bring it up to 1200, I get a smaller swing (maybe 150 rpms). And, I get it under a load (uphill) when driving at 40mph or so. Not totally trusting the guage, I hooked VAG up and went through the readiness cycle. Sure enough with the accelerator floored and the governor holding tests to 2200rpm, I'm still showing a continuous rythmic swing in rpms on VAG between 2200 and 2140 mostly. Just curious if anyone can shed some light on why this would happen since I'm assuming the fuel/air ratio is not consistent, particularly since I'm throwing CAT codes (that's another story). I can run the same tests on my wifes A4 Cab with the 3.0 and it is steady as a rock.
thx,
AJG