I have a 2013 Ford Explorer Limited 3.5l and I have a very intermittent (after roughly 500 miles of driving) P219B engine code. The car has new spark plugs, fuel injectors, no intake leaks, no exhaust leaks, does not have a bad purge valve, and no type of misfire or any other computer recorded information. MAF sensor has been cleaned and also has a newer air filter. Oil dip stick and oil fill cap are both seated correctly too. Wondering what could be causing this intermittent code to come back.