2004 F115 sputtering surging not getting RPMs

[billygoat]

My 2004 F115 is sputtering or surging when accelerating and not getting above 2500 to 3500 RPMs. This has been an ongoing problem, and intermittent in that sometimes the engine runs fine. After the second trip to the shop, it has started again and is getting progressively worse.

I have had the following work done on the engine:

-cleaned fuel system, new plugs, cleaned vapor separator, new fuel filters, new injectors, new fuel, installed addition fuel water separator - engine ran fine for a few months then same problem

-back to shop for cleaned fuel system including vapor separator, new injectors - engine ran fine for several months then same problem

-back to different shop which found several cylinders not carrying a load, dirty injectors, some metal in VST because of fuel pump coming apart - the fix was replacing fuel pump, pump dampner, fuel filters, gasket, VST bottom, plugs, and re-install injectors after cleaning and flow testing. Engine ran fine for several months but has started surging, running rough like missing cylinders again and has become progressively worse only getting up to 2800 rpms recently

Any comments or advice is appreciated as no mechanic I have been to has been able to diagnose and cure the problem. Running out of options short of another expensive trip to a different mechanic.

[JONSNELL]

What about your fuel supply - ie tank , filter and maybe an anti siphon valve.

If you have the engine clean and operating are you able to try running it on a portable tank ?

[billygoat]

I have not tried using an auxiliary tank yet, but will. When I get it back from the shop it runs fine. Once the problem comes back, and gets progressively worse, it seems that using a separate fuel tank would not resolve whatever it is that is causing the problem in that if there is a fuel flow issue inside the engine using another fuel source could not fix it. I will give the auxiliary tank a try. Thanks for your comments.

[rodbolt17]

think about it.
once the shop cleans the ENGINE fuel system and it runs well.
where does the debris come from to clog it all up again?
not the first time I have had to replace ALL rubber lines under the hood and all the way back to the tank.
not the first tank I have ever had to replace.

this stuff did not last forever even back when we had real gasoline.

next time ask the shop to allow all the rubber lines to dry overnight and then inspect them with a good light.
any of that yellowish dry sheet on the line will scrap it most likely.
the ethanol in the fuel will dissolve it again and keep feeding it to the VST.

[kyleroberts1943@yahoo.com]

Had the same problem with my 2001 115 four st

I found that the liner in the fuel suction was restricting the fuel sometimes. I found this by using another tank and new hose. The bad hose was a new hose but had a liner in it that was squeezing closed when it had load on it. It sonds like your problem is on the suction side of the fuel cycle.