Volkswagen cc could trouble code 2187 be caused by faulty fuel cap

Question

gas cap is always loose when fueling up

Answer 1

P2187 Bank system too lean at idle,  can a gas cap loose cause this code? No. You have a lean air to fuel ratio. Lean air  to fuel ratio can be causes by a MAF (mass air flow) that is faulty or even a bit dirty, A MAF air flow cleaning may help, Vacuum leak can cause lean idle, Fuel pressure low or even a  partial clogged injector, Above all it may be time for a tune up, worn sparkplugs do cause lean air to fuel ratio,And if you have a faulty gas cap replace it,Fumes are gasoline also.