This is for my TrailBlazer 4.2L....

Problem, engine loses power when gas tank gets to quarter of a tank. (however it has occured at half a tank) If you try to push the pedal more than lets say 2 percent of travel, it will cause backfire and popping in the exhaust and not accelerate. if you keep it at that 2 percent area it will maintain a 10 to 20mph speed. It will stay this way till i fill up with gas.

So as i am traveling down the road it will be running perfect then all the sudden it feels like someone has turned the motor off and i am coasting. engine stays running but has no power at all.

I have changed the front o2 and have ordered plugs from the dealer but they won't come in till monday. Also, it has a relatively new fuel filter.

at this point, i am thinking these could be the culprits
1. the fuel pump is going out.
2. the cat is clogged.
3. i need to run it into a river.
4. some other ghost

 

Also, popping/backfiring with loss of power means your timing is off, but it doesn't sound like it in this situation.
Philip S.

 

thats what it almost feels like when the power loss occurs. i can be driving down the Istate doing 70ish and everything is good, then it will just do it. feels like a 6 cyl on 4 cyl's. worse actually.

i wonder if the computer is bad?

 

Is the fuel filter in the right way? There is only one way it is supposed to go. It could be a fuel pump also. Check that the mass air meter is ok, sometimes they get crap on em and they will act all f'ed up.

 

fuel filter is in the right way. the lines are on the same end and clearly marked. this engine don't have a mass air sensor. intake straight to the throttle body.

if it was a cat converter, it would do it all the time right? at least i would think so.

i am leaning towards the fuel pump. considering it does it when the fuel level gets low. either that or my fuel level switch is bad and i am getting false fuel level readings.

 

Seems most probable to me...

 

pick-up tube loose, corroded 1/2 or further down, sediment build up in the pre-filter, etc...