Engine acts like it hits boost, without a turbo

Minty Ferd

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I have a 89 F350 7.3 idi with an unknown amount of miles, my guess is it rolled over twice so 214k miles. IP is definitely a replacement because it's not painted. Previous owners were crackheads so no info from them.
So I accelerate in third gear (ZF5), steady pressure on the pedal, and it hits 2300 and then acts like it hits boost. Revs up faster, sounds different and keeps going all the way up till 3400 when I shift, because i don't want to go any higher. Mind you I've not pressed more on the gas pedal. It doesn't do it as much in 4th, and not at all in 5th. Haven't tried 1st and 2nd. Has anyone else experienced this? I'm thinking the IP could be going bad, and I have a turbo idi IP ready to swap in if needed.
Also when downshifting or coming down from high RPM, it'll lunge forward, as if I tapped the gas quickly. I know it's not the clutch slipping as that's all brand new. So it's slowing down from 3000 rpm, and acts normally, then it jumps back up 100 more rpm, and continues acting normally. It'll do that only coming down from high rpm, and only like 3-4 times.
All sorts of weird things, I'm wondering if it's just the IP.
 

Cubey

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Stock IPs aren't (always) painted, I don't think. I suspect my E350 RV has it's original (under 100k) IP and I don't think it's painted, unless it's painted silver.

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Air intrusion and/or heavy winds can cause the "boost". My NA F250 did that randomly a bunch in the heavy winds of Wyoming in 2017 but otherwise had no air intrusion.
 

CharlesG

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How much fuel did you have in your tank when this happened? If you were low on fuel, the fuel could have sloshed forward and back exposing the fuel pickup and allowing air to be drawn into the system. That would produce the same symptoms you desribe.
 

OlKoot

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Return line backflow preventer. This helps also, air may be getting in fro
M the rrturnlin. We put them in back in the early 90's at Ford to eleviate tthi. Check all yur connections, and clamps. First. Filter integrity next, includingdrainin any watter potential.
 

Bio-Bradley

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Might be an air intrusion from return lines. Might be from low fuel that's allowing air to get sucked into the fuel lines when the fuel sloshes around. Also, the fuel tank sending unit's funnel filter may have fallen off. These are notorious for degrading over time and falling off. If the fuel funnel filter falls off, your truck will behave like it's running out of fuel at around 1/4 tank. At least, mine did until I replaced it. If you are around 1/4 tank of fuel and experiencing the surging in the engine you are speaking to, could be that air is being sucked into the fuel line because the fuel tank sending unit is no longer able draw fuel from the bottom of the tank. Good luck!
 

Finn

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Check the oil level. If the injection pump shaft seal failed and filled up the oil pan with fuel, at some point crankshaft windage will cause liquid to be carried into the intake manifold. This usually happens at about 2300 rpm, depending on how high the oil level in the pan gets.

Alternatively, continued presence of water in the fuel can destroy the pelethane ring in the injection pump, creating debris that lodges in the metering valve.

Either scenario calls for a pump rebuild.
 

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