car feels slow when the tank is full?
 

My problem is when my tank of fuel is full - my throttle feels really sluggish and slow. But when the tank is almost empty throttle feels VERY sensitive (like it should be from the factory, I guess). And it is not because of the additional fuel weight, if a big friend of mine sits in my car when the tank is almost empty - throttle is still very sensitive :(

My only guess is fuel pump, as I cleaned it several times (here we have very dirty gasoline sometimes), but I can't imagine why

Maybe it is somehow connected with the self-learning ecu?

Gas weighs 6-7 lbs per gallon. Multiply that times 19 (our tanks capacity) and its a decent amount of weight.

^Yep, gas weighs a lot. I always keep my tank around a half tank or under just to keep weight down a bit.

I move slower after a big meal, too.

Maybe my EVAP system is dirty or something is wrong with it. Has anybody dealt with it?

Any chance you are occasionally using a lower than recommended octane? If so, the ECU might be pulling some timing.

EVAP problems should set a check engine light -- is that on?

:icon18:

Try running race fuel and see if it helps :D

the problem is that it is not 100% consistent, so I can have laggy throttle pedal when the tank is almost empty, but most of the time it happens when the tank is almost full or at 3/4, 2/3... there is some connection, I'm sure!

maybe I should do this ITB: Knowledgebase - Infinitihelp.com Forums - VENT CONTROL VALVE REPLACEMENT ?

I'd still attribute it to the weight. I actually have heard that a gallon (of water at least) is closer to 8-10 lbs so when adding 15-18 gallons you might be adding the weight of another person pretty easily.

You are promoting rust and condensation in the upper half of your tank, then.

Not when the fuel is constantly getting sloshed around during driving, that can't really happen. Unless the car is going to sit for a while, then it absolutely could promote condensation and rust.

Weight of 1 US Gallon of Gas = approx. 6.073 lb

So 6.073 lbs X 19 Gal = 115.387 Lbs

what octane are you running? Please dont say less than 93 :shakes head:

gas is lighter than water

really??? how does plastic rust???

Your butt dyno needs recalibration, this is a farse.