Fuel Shudder?
 

I'm noticing a shudder during moderate to heavy acceleration. Something like a 45-60mph in 5th gear situation, although it happens other times too. Feels like a miss or a starved carburetor on a gas motor. My fuel filter is new and my milage hasn't changed. Fuel pressure shows 14psi when cruising and this acceleration situation pulls it down to 10psi. Any ideas are always appreciated!

mine does the same thing. after doing some talking and research i think its the injection pump not being able to keep up with the bigger injectors. a buddy of mine actually ran the pump out of fuel during a burn out and we had to reprime the pump. now just saving up for a hot rod vp44

Thanks for the reply! I hope that's not it. I haven't had any DTCs when checked. Maybe it's hasn't reached the point to be detected as going bad? Also, this problem stems from a weak injection pump that's ready to crap out?

i dont know if it is necessarily going to crap out. mine is only 5 years old but its stock so it just seems like it can't keep up to me.

When I posted the thread on Tuesday, it had been in the 30s here for a few days. This morning it was 34 and it acted up. This afternoon, it warmed up to 65 and the truck ran great under all acceleration tests. Any thoughts?

Mine does it too, I have a very large Racor 2 micron fuel filter set up hanging off the frame rail, and had the TST Comp Box on level 5, it was very cold for Memphis, in the teens & 20s, I also have 125hp injectors. Changed the filter, no difference, turned the box down to level one, problem went away.

Ordered a sump and twin 16 psi, 150gph Holley Billet Fuel pumps as I think my twin stock replacement lift pumps can not handle the thicker cold fuel and 2 micron filter with the mods I have.

Hey. Mine started doing the same thing. I thought it might be the inj pump

Thanks again, Guys. I have also wondered if the cold 2-cycle oil in my fuel is causing a fuel-thickening issue. Iowno...Still, the truck runs like it should if I really hammer it. I cant understand why the issue arises more under milder acceleration. Seems to buck hardest if I maintain boost at 25psi or so. Accelerating beyond or letting it drop clears the issue up.

Do all you guys have your grid heaters still in place i live in colorado and see temps bellow 10 i also run 2cy oil these injection pumps IF working properly can handle 550hp safely so injectors below 175 shouldnt mess with it to much as for the injection pump being ran out of fuel that is most likely a lift pump issue as with ANY injector size increase you should be runing a 150 gph lift pump if your going to put on a hot rod vp i woupd suggest that you get 165gph lift pump or larger and bigger injectors and not to run at the max of the injectors but rather 50-70% of the injectors and let your timing boxes do the rest and i would also asume you have head studs if spending 2000$ for a hot rod vp ?

I do have my grid heater in place. I have the HO pump that was replaced under warranty in '05. My lift pump is a Raptor 100gpm. And, the truck runs great when really pushing it. The problem is easing into the throttle at cruising speeds. It bucks, for lack of a better description.

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Sorrt, that's 100gpHOUR LP.