Filling gas tank makes car run smoother?

[MankDeems]

If I fill up from 1/4 - 1/2 - 3/4 etc the car seems to run really smooth compared to before filling the tank. Have an 05 v6 with an eaton supercharger kit and 93 tune. Fuel cap has been replaced twice now (i keep having the gas gauge fall to E and getting a code for high sensor reading from fuel tank, which i think is related to the sulfur deposit on the pump scandal.) Why would filling the tank make the engine super smooth and even give me a few burbles and pops out the exhaust?

Currently battling a misfire in cyl 5, so I cant really test anything until my new ignition parts come in.

 

[Jim Draker]

I'm having similar problems under 1/4 tank was cutting out & putting it in neutral & restart would fix for a few minutes, fuel gage dropping to E, & now has a permanent misfire & throwing about 8 codes! About ready to take a sledge hammer to it!

 

[StockishS197]

Not sure on the 4.0 but could it be EVAP system related? I have noticed something similar on my 4.6 3v where start ups hot and cold are smoother when above have a tank.

Maybe check for any potential leaks and/or ensure the system holds vacuum. Could also check the canister purge valve and solenoid.

 

[Robert Larimer]

If I fill up from 1/4 - 1/2 - 3/4 etc the car seems to run really smooth compared to before filling the tank. Have an 05 v6 with an eaton supercharger kit and 93 tune. Fuel cap has been replaced twice now (i keep having the gas gauge fall to E and getting a code for high sensor reading from fuel tank, which i think is related to the sulfur deposit on the pump scandal.) Why would filling the tank make the engine super smooth and even give me a few burbles and pops out the exhaust?

Currently battling a misfire in cyl 5, so I cant really test anything until my new ignition parts come in.

I think it has to do with the wonky 2 sided tank our cars use. When one side gets low then fuel delivery problems start. There are even 2 level sensors, one reads full to 1/2 the other reads 1/2 to empty.