Hyundai Repair: Hyundia repair, air flow sensor, santa fe hyundai

Question
I E-mailed you about a 2001 Santa Fe Hyundai the other day with a code p0171lean system bank 1 and you gave me several reasons.  When we removed the cover over the exhaust manifold to get to the oxygen sensor we found a long crack in the exhaust manifold.  Could the be cause of the poor running condition?  what effect can this have?

Answer
It's doubtful that a cracked exhaust manifold will cause a P0171.  Typically, this causes little more than a noise due to the exhaust leak and a diagnostic trouble code indicating slow oxygen sensor response.  This also should not cause the vehicle to run poorly.  

A faulty air flow sensor or a vacuum leak can cause the P0171 and the vehicle to run poorly.