Car drives better on a near empty tank?

Hi,

I seem to have come across a funny pattern, my car seems to drive
better(more responsive, less hesitation during acceleration) when the
fuel tank is close to empty and the fuel light comes on. I am yet to
confirm the pattern for sure, but could there be a logical explanation
for it?

 

Less weight in the car?

Hugh "a pound of feather or a pound of bricks" Graham

 

when you get to the end of a tank, by then the lighter aromatics in the gas
are finally being sucked into the fuel system. thats why its always a good
idea to bounce the car up and down a few times after refuelling, to mix the
aromatics from the refining process.

 

(eswaroop) spake unto the masses in

Don't keep the tank empty. It's hard on the fuel pump and contributes to
premature fuel pump failure.

Also, water will build up in the tank much faster due to condensation from
all the exposed tank surface. This is bad for rust, the fuel pump and the
injectors. Keep the tank as full as possible at all times.

Any "responsiveness" is most likely due to the fact that a hundred pounds
of gas is absent from the car's weight.

If your car has an actual problem with "hesitation" that is ameliorated by
keeping the tank empty, that would only mask trouble. Get it looked at.



--
TeGGeR®

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This is not actually a power gain during the empty tank but rather a
power loss on full tank, my car used to drive normally till sometime
before, until it actually started playing tricks. Sometimes, even on a
near full tank it drives well.

 

Huh? Gasoline is a mixture of miscible components - there should be no
separation into layers and certainly not in a car which is driven over the
usual bumps. Think about it: if it got layered in your fuel tank it'd be
layered in the storage tank - you would never get a consistent product
delivered at the pump. Aromatics have never been the lightest components
in gasoline and the lightest one is banned in most places now.

Rgds, George Macdonald

"Just because they're paranoid doesn't mean you're not psychotic" - Who, me??

 

The fuel is probably getting hot (friction + pump's heat) when the tank
is low. See if your intake manifold is being heated properly by engine
coolant. You could also have dirty injectors or a failing O2 sensor.

 

Hi,

The problem is that the effect is not consistent. Sometimes, the car
runs well even on a full tank (have to check if it were always on
sunny days!)

Also, when it runs bad, the accelerator pedal seems heavy.(maybe coz I
am stepping more on it.)

I also thought of a bad o2 sensor, can someone think of other problems
which might be noticeable because of a bad o2 sensor? (IT is not
throwing any code)
Maybe that might pinpoint towards something. Also, will/can o2 sensor
problems be intermittent?

The car hesitates and stumbles during acceleration or surges and
stumbles. (not a smooth acceleration)
Sometimes it does not respond to my stamping on the gas.

It is really bugging me, and I have been trying to figure out what is
wrong for the past 1 month!

Thanks

 

Maybe too obvious but - e.g. 15 gallons of gas weighs about 100 pounds...

 

It still pulls harder and stronger even if there are like 3 to 4 125-
150 pounders (people) in the car. The difference is just too drastic
to be just due to 100 pounds of fuel.

 

Less weight.

 

and you're running on 2 cylinders.

 

Could you add info about year, model, engine, transmission?

Also, you say that with a full tank it is intermittent (sometimes seems
good, other times has these drivability problems). Is the problem also
intermittent with an empty tank, or is it ALWAYS good with an empty tank?

Lastly, have you confirmed that your check engine light can actually light
up? It should come on as a test for a moment when you switch on the ignition.

-Arthur