The failure of the air pump itself will not affect fuel consumption BUT stuck open SAS valve WILL because it will produce a vacuum leak at it's vacuum line.When it fails...it always fails in open position.pauleads wrote:Would failure of this pump lessen gas mileage or cause other problems if left like it is?
Usually,sas valve is the first one which fails in that circuit and lets water from condensation directly into air pump and after that...from air pump through air filter and MAf...into engine.
If your sas valve is stuck in open position,air pump is not the only thing which will fail because of that.Maf is also in danger.
My suggestion is to search for "sas delete" on this forum.