Stumbles after a long drive

[Ole' Blue]

Hey guys, my '93 IC with a Getrag has started a new problem. After a long highway drive (about 45 minutes) it will stumble 2 times. It's a bit difficult to describe, but with my foot steady on the gas (65 mph, 2100 RPM, 10-15psi boost, 600-700 EGT) it will jerk as if the engine has died. I instinctively pull my foot off the gas, and then press it again. It doesn't want to go yet.
Within a few seconds, it will go again. A couple seconds later, it will stumble a second time. A few more seconds, and it's good to go for the rest of the drive. Boost drops off, but not instantly to 0psi. I haven't tried pushing the clutch in yet to see if it idled. It's only happened 3 times, since I rarely drive that far. The most recent thing I have done to the truck is to grenade the original turbo (was making over 30 psi of boost), then install a HX-35 with a 28psi wastegate and turn down the fuel a little bit. It hasn't happened every time since installing the turbo, so I'm not convinced that is the problem. Any ideas of what to check?? If I drive it long again, I'll see if it idles. If so, it probably means boost problems, right?
Oh, one more thing. After it happened the first time, I replaced the Fuel filter, thinking it may have been water or blockage. Thanks.
Kevin

[ahale2772]

when it "grenaded" the turbo, did you check your Intercooler for related shrapnel?

Im thinking the issue is not related to air, it wouldnt die all'a'sudden like that if it was air (not unless you had a major leak)

im gona say its still fuel, it would be wise to check the lift pump

[ellis93]

^^^X2
Only other thought would be the FSS if your not using a pull cable to kill it. Their inner electric coils can get weak or spade terminal will get loose and cause this. I had this happen to mine.

[Mark Nixon]

Sounds for the world to me like a bad connection on the FSS.
My old '91 flatbed had a loose splice connector (NOT my doing!) on it and would get all funky like that, until I changed it and the problem went totally away.
Another truck I owned had a loose spade connector, same deal, run erratic at normal speed, but slow down or speed up and it seemed normal.

Mark.

[Ole' Blue]

Thanks guys. I'll check the connector on the FSS. I didn't check the intercooler for any shrapnel, do you just remove the boots and look inside? Or do I need to remove the IC and shake it around? I've never even inspected the IC before! The FSS sounds like the most reasonable possibility. Just curious how it always happens after that long drive. Is there any way to verify that the factory lift pump is flowing (other than a gauge)?
Kevin

[ahale2772]

not any definite way to check the lift pump besides a guage, a 20$ special mechanical kit from advance would probably work, and be a good thing to have.

best way to know if they IC has pieces in it is to see if you have all the pieces from the old turbo