Hi, 95 SSEi with 158000 miles, runs bad under load (high RPM) if under 3/4 fuel level. When I fill up, she roars back to life. I have no SES light and and have checked everything under the sun (and under the hood) and can't seem to find the problem. Any ideas? The fuel pressure (KOEO) is 47psi. Help please....... Thanks

Is the 47 lb pressure when it is down to the 3/4 tank with the problem showing its face?
Guess you have replaced the fuel filter, huh?
When you get down to 3/4 tank, have you eyeballed the tank from the bottom? Not sucking the bottom in is it? Trying to figure out if you are having some wild venting problem.

I changed the fuel filter and also checked fuel pressure at 3/4 to 1/2 tank while driving. the pressure appears normal, rises as vacuum leaves regulator as designed. I did also check for tank suck and even removed the cap while driving. For the record, I drove alot today and when tank got to about 5/8 tank, she started runnin like crap again. I filled up, and ZOOM-ZOOM again. If I can't fix this pig, I may have to cook it! Thanks

If you don't get more input on this, I would have to suggest dropping the tank and see what the heck is going on in the pump/pickup area or if something has come loose. :?:

Was running this past some of the gearheads. When you "fill it up," do you mean "all the way to the top?" Or just 5 or 6 gallons?
If you had a bad feed from the sending unit, for instance, and was closer to empty when it is reading 3/4 tank... well, you know where I'm going. A corroded ground for the sending unit can throw the fuel gauge off.

The car must have over 5/8 of a tank full or it runs baaaaaddd. Sounds crazy but it'* true

We're wondering how accurate the fuel gauge is. If you add fuel at 5/8 of a tank then how many gallons does it take to fill it?

My 92 SSE had a 95% clogged fuel pump sock. It would show pressure but did not have the GPM required for higher RPMs.

Drop the tank & see what you really have inside.

I've seen a lot of things go wrong, the 1.5 inch hose between the pump and sender gets holes/tears in it, or it sometimes dissolves with the use of strong injector cleaners. And if it has a pulsator instead, they'll bleed off pressure sometimes. Could be a clogged sock, but I've never seen that happen.

If you do find out please let me know, i am having the same issues with my vehicle, it feels like it has more power once the tank is full, anything under half and she feels a bit hesitant. Then again i am pretty sure i have a missfire while in 3rd or 4th.