Okay, I got a problem.  I have a 1997 Jeep Grand Cherokee Ltd.  It has the 5.2L V8.  I have done intake, exhaust and have Accel Plugs and wires (25K on the tune-up).  I regularly change oil and use fuel system cleaner.

When I drive with less than a quarter of a tank of gas I tend to get a loss of power.  If I keep on the pedal the truck takes off okay, losses power, bogs down, and then takes off again.  It only really happens when I am heavier than normal on the pedal.

It almost feels as if I am not getting fuel to the engine, as if I quickly run out of gas.

I run regular gas and use Exxon mostly (or Valero).  Could it just be a fuel filter or is it some other rare occasion that seems to happen only to me.  I can't figure it out!! I need help!  

Could be several things; water in the fuel tank, pickup tube in the tank not reaching the lower part of the tank or something floating around in the tank that only obstructs flow at a certain level. Since it only happens at less than a quarter tank, I would not suspect the filter but they aren't expensive , so you could try that first.  

an O2 sensor can make it act like that after about 100k all O2's need to be replaced (in my opinion i replace things before they go bad and as budget dictates)or if it has an after market (replacement) gas take alot of those don't have baffels in them but a 97 shouldn't have one unless wreaked. i know this doesn't jive with the 1/4 tank thing (o2 being bad) but vacuum no baffels and o2 are all i've got right now.  

swap t a new fuel filter and clean the tank i had a 5.9 act the same way and that fixed it.  

I would pull the pump and check for pin holes in the pikup if your problem only happens when your lower on fuel. Injectors don't like to open when there is air or low pressure due to you fuel pump trying to pump air. Its like trying to suck through a broken straw. Nothing but bubbles.  

VACUUM LEAK! if you did an intake, more than likely you did not use a torque wrench for the bolts, take it off and adjust it properly.this should help a little. it has nothing to do with power loss, but its a start.

also, PCV valve may be clogged, or old, replace it, its $3.00.

re-torque your intake manifold. the bolts become loose over time, and i am sure in the tune ups you may get, the techs, or you dont really check for that, that will cause a power loss.

***loss of vacuum = equals loss of power. and engine needs vacuum.  

To the best of my knowledge vacuum leaks reak more havoc at no or part throttle.  Full throttle is where vacuum leak problems go away since your throttle body is wide open and there is much less vacuum.  

excactly, so between 30%-60% he might be feeling the loss in power, cause the engine is trying to make up for the loss of air/fuel mixture. the easiest way to check is get some brake cleaner, and spray where vacuum lines are. and around the throttle.

if its not it. the adjustments are still a good idea, my zj idle alot better when i did them.

i thought of something else. pull out the fuel pump, get you a multi meter and check for un needed resistance in the module. corrosion could very well be robbing your engine of power.  

your fuel pump should have measurements for resistance in a Haynes book they sell at auto parts stores. if not, all data is your best bet.  

and benjorno99tj, please tell me how you stroked out that 4.6. im getting one soon.  

Hopefully i didn't write that wrong and mislead people, but its the 4.0 that i stroked to a 4.6.  what i did was got a 4.2L crank, aftermarket 4.2 rods and .030" over 4.0 pistons. i went .030" over since my cylinder walls were about .015" out of round. you need to space back the bridge between the main caps to make room for the longer stroke. You will need a new pilot bearing for the end of your crank to match your tranny. You will also need a spacer for the nose of the crank because the nose is longer on the 4.2. I went with 24lb injectors, never touched the computer. Will find out in a few weeks if it passes NY emissions. One note, get the main bearings for your BLOCK. The bungholes I ordered the parts from sent me bearings for the crank. The locating tabs are in different spots!