Volvo Repair: Generic code P0171, air flow sensor, purge valve

Question
Good Morning James,
My question concerns a 1998 V70XC AWD that has a recurring code P0171 which I interpert as a EFI 231 code. The engine oil is fresh and clean, the exhaust is leak free, the EVAP system is not over fueled nor is the purge valve stuck open, the fuel pressure is correct and the regulator does not leak, the air flow sensor works properly and a new sensor was substituted with no change, the 02 sensors are both new with the patch harnesses installed, the 02 sensors are operating correctly. The car runs well and has no fuel economy issues. The problem does not occour at idle. When driving on a fresh set of adaptives the LTFT will go to -9% and lower within 2-3 miles. Any ideas? Thanks for your time.

Answer
Your fuel trim could be going lean for several reasons.  The fact that it goes bad after several miles makes me think that it has to do specifically with the car heating up to operationg temperature.  It could be a boost leak (turbo only), malfunctioning fuel injector possibly leaking.  I can't really think of anything else that you haven't checked already.  Just double check EVERYTHING that affects fuel delivery, and air induction/measuring into the engine and you should find the problem.  It may be hard to find but it HAS to be there otherwise the car would be operationg normally.  If I think of something else I will send an addition to this answer.  Hope that helps.

James