Losing power around 3500-4000 rpms, sputters a bit. No CEL
 

Just as the title says. Tons of power until the power band. Then it's almost like im running outnof gas. Doesn't start hard, at least not hard for having msd, cams etc.

Plugs? Fuel filter? Of course I'll ask my gm techs at work but I won't see them until Monday

Put a fuel gauge on the rail and tape the gauge head to the windshield. Drive the car as you want and note the reading. If it drops much below 40 psi, you have a fuel pressure problem.

There is a gauge there already. Can I tell from idle?

The more i think about it, the more i think its the fuel filter. I ran the car pretty low on gas, noticed the issues...filled it but still same problem. Prolly gunked up the filter. Will change

sounds like fuel pump is going bad. pump is in the tank and is cooled by the fuel. if tank is run low on fuel the pump gets warm/hot and if its close to failing already it will fail.

For the record, the fuel level will have no direct effect on gunking up the filter. The gas is sucked off the bottom of the tank, whether it's full or almost empty.
Agree though, it does sound like a fuel starvation problem. As the engine is asking for more at the higher rpm's, it might not be getting it....pump not keeping up or filter restricted.

If a fuel system has a lot of crap floating in it then the first time the tank runs low it can cause issues. I had two old school cars come into the shop that ran out of gas and would not restart. About 10 PSI of shop air blown into the tank through the hose would get them started, in neither case did the customer opt to remove the tanks since these where older cars. I also did fuel filters and a note on the work order that said customer refused a complete repair.

If if turns out that the in tank fuel sock or fuel filter are causing the issue you should clean out the tank and I would think about replacing the pump because a pump that starved for fuel would be suspect for failing soon.

The issue you described is normally either fuel pressure or exhaust back pressure. You will need to be checking the fuel pressure while the failure happening so checking it at idle will not help much.

filters rarely are an issue ,some people never replace them ,but for $8.00 its not a bad thing ,these guys no whats going on

As always thanks for the help guys.

The fuel gauge read 35 while idling.


Lifted up the carpet in the fuel tank area and found what I believe to be a back door to the fuel pump/gas tank. I think I'm going to replace the pump and filter in the spring. My car is pretty well modified so I think I should get the best performance pump. I'd love to hear suggestions. Thanks!

What are other signs of back pressure issues?

Well there are no other symptoms. In fact if the car is starving for fuel you should be getting a check engine light with a lean error. A restricted exhaust will not through a code.