At 06:30 PM 12/4/2009, Michael Hart wrote...
>My '97 Jetta ... The codes are
>P0171 P1128 P0440
>
>I've replaced the Air Flow Sensor, checked for vacuum leaks, replaced
>air filter, plugs, cleaned all air inlet pies & boxes, all with with
>no improvement.

Sure sounds like a vacuum leak. Did you check the purge valve, and the
connections between it and the EVAP canister (which I think is in the
right rear wheel well)?

Pic:
http://gti-vr6.net/library/engine/P5150220_EVAP_valve+PCV_valve.jpg

You can also get a P0440 if the gas cap doesn't seal correctly. I
suppose it could cause the other codes, by allowing excess air to be
sucked in through the purge valve.

Other than that, I think all these codes are a result of readings from
the front O2 sensor, so it could be failing. But, I'd expect some other
codes, too, if that were the case.