Losing power at 1/4 tank

[thetubageek]

My 2014 Fusion started having issues with driving some time back.

 

We replaced the battery and thought the issue was fixed. But, the next time my tank was starting to get to a certain point, it would not want to drive.

 

In a nutshell, it feels like it's completely losing power; it will stutter/lurch or it will go for a while before the RPMs bottom out and I'm stuck going under 20 mph. When this is happening, I can have the accelerator all the way to the floor and it simply will not respond.

 

I can pull over and shut it off for a while and it will come back to life when I restart the engine, but that's a short-lived effort before it either loses power as previously described or completely die.

 

Here's the weird part: it does this when the gas gauge is at 1/4 tank.

 

Now, my check engine light is on and it is registering an issue with the catalytic converter (a $500 fix I certainly cannot afford right now), as well as an O2 sensor issue (recently popped up and a cheaper fix, but I might as well get both things fixed if I'm going to do that). 

 

So, what is the issue? Is it the converter? Is there something in my gas tank that causes this to happen when I hit 1/4 tank left? What do I need to look into buying/repairing?

[propwash]

I had a similar situation with a different car (not a Fusion.)  Down around a quarter tank or so it wouldn't want to idle smoothly, and the acceleration was really slow.  It turned out to be a weak fuel pump.  My theory is that the weight of a full tank of gas gave a little boost to the fuel pump.  As the fuel burned and the level in the tank started dropping, there wasn't as much fuel there to help the weakened fuel pump do its thing.  I discovered this by checking the pressure in the fuel rail.   With all the modern electronics on your car, though, I would think that there was some kind of notification in your instrument cluster or a CEL light coming on that should notify you of a fuel pressure problem.  Again, I'm just guessing here.  I'm not familiar with all the information that is available when the various warning lights or messages are displayed.   You might get some kind of a message telling you if your fuel pressure is too low.

 

Keep us advised of what you discover, and good luck.