Car runs like crap when I get below a half tank of fuel

[e3mand]

Hello all,

New Member here, I drive a 2000 Mazda Protege ES. I have only owned the car about a year but I've decided it's time to address this annoying issue that I have sometimes.

Whenever my tank gets below a half of a tank the car starts to misfire under acceleration like it is not receiving enough fuel. Sometimes it doesn't happen and sometimes it does but as of late it has been more frequent. Any thoughts or experience in the past with this issue. Any feedback at all will be greatly appreciated. I'm not sure if it is related but the car is awful to fill up, I have to go super slow or the tank will overflow.

Thanks!

 

[concept]

Regarding your fillup slowness, there is a non-return flapper valve, located in the filler tube (in some Proteges) that sometimes gets stuck in the filler neck, restricting fuel flow at fill up.

Does your car show any codes?

 

[e3mand]

Okay I will check that out. The only code it currently shows is the P0421 but I am using the non fouler trick to get it through inspection. Although one time when I started experiencing the misfires the CEL started flashing and it was a misfire code.

Thank you for your help

 

[concept]

Misfires can be caused by a bunch of things, coil packs, distributor, wires, plugs. If it is because of low fuel pressure, then the fuel pump is the likely culprit. Do you have a service manual? They can come in handy for troubleshooting each potentially bad component.

 

[e3mand]

It must be fuel related because it only happens when fuel is low. I would think that fuel pressure is constant regardless of the level in the tank though? Am I wrong?

 

[concept]

It would be if the fuel pump is good. Sometimes you can get good information from a Mazda service manager if you ask the right questions. I would call and ask if he's ever had other customers come in with the same issues. Say you'd like to try to get a good idea as to the cost, over the phone.
Years ago, my wife's 86 Honda Accord's blinkers stopped working. The service manager at a Honda dealership told me he's seen many Honda with that same issue. He then told me to push and pull the emergency flasher switch, multiple times. It seems power for the blinkers had to get past the emergency flasher switch, which was very infrequently used, allowing its contacts to build up an oxidation layer. Exercising the switch cleaned them up enough so they could transfer power to the blinkers.