Originally Posted by SSEBONNE4EVA
Check your gas cap if it is venting properly.
There should be no difference in pump performance between 1/2 and full tank
as the filter sock is at the bottom and totally submerged.
Have you checked pressure at the fuel rail? Changed the filter?
Adding mystery oil to the tank will dissolve any rust and sediment in the filter
sock and lubricate the pump.
Water in the fuel could also cause this.
I didn't think emissions-controlled cars had vented gas caps. I lost my original cap... I bought the current cap at a gas station about 4 years ago.
With 1/2 tank of gas the strainer is usually submerged and works fine, but I suspect under heavy braking the gas is shifting around in the tank. I'm not familiar enough with the layout of a gas tank to know exactly what'* going on. But there is a TSB regarding this condition and the solution is to update to the newer strainer.
The problem has been happening since last summer. I changed the fuel filter last fall. I added a couple of cans of dry gas this winter. Problem persists.
Mystery oil is an interesting idea, what brand do you use? Marvels?