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2008 F-350 boost dropping off and no power

7K views 47 replies 5 participants last post by  Isaac313 
#1 ·
I have a 2008 Ford F-350 6.4 PSD with 120k miles. The truck is bone stock, service truck. It has tons of power up to 55mph but right after that it just falls on its face and the boost starts dropping off. I think its right around when it shifts in 3rd gear on WOT, it just loses its power.

I have a AE scanner and the truck is throwing no codes.

Any help?
 
#4 ·
Does vgt duty cycle change at all while driving??????? If not I would put money on an electrical issue.
 
#6 ·
When you cycle the key on does the actuator actually move?
 
#9 ·
I think I got him mixed up with another guy with the same problem on here... Yah, ebp numbers would tell the story.
 
#16 ·
Put a new egr valve on it just because and it made no difference. Also swapped a different throttle position sensor on because we have a parts truck. It made no difference. I'm not finding anyone online with this similar problem. I see people losing power when their trucks go into regen but this isn't my problem.
 
#17 ·
what's been done to your truck? It might help to know tuned deleted etc...?
 
#19 ·
Hmm, really no codes? Do you know any shops? Most of them should have scanners that can see codes that regular OBD scanners won't.
 
#25 · (Edited)
Not necessarily. Some run great for a while then bog down. Let cool off and they'll run good for a while. Remove the secondary filter (the one on the engine) and shine a light on the fuel. See any sparkles?

View attachment 487954

Kinda like that.
Checked this today. Fuel is clean as pin, no sparkles, no nothing.

When I pulled the filter off I turned the key on just to see how quick the bowl filled up, it seems kinda slow and it had bubbles in it. Is this normal?
 
#24 ·
^^^^ that
 
#28 ·
Random thought... Is the coolant in the fuel cooler topped off? I know of a few cases that low coolant in the fuel cooler caused some power loss. If it is too low it will throw a code, but not always... What do you think Lox?


I have a friend that ended up having his fuel system replaced because the dealer failed to check the fuel cooler itself... His ended up throwing a code after the work was done and luckily his service manager wasn't a d1ck and ate the repair bill for the fuel system.
 
#30 ·
Well crap lol.


The hpfp could still be an issue, the pcv or vcv could be taking a sh1t on you. If the rail pressure doesn't jump or fluctuate I wouldn't think its the frp sensor.
 
#33 ·
Let it warm up and pay attention to it for a few minutes. Just watch the graph for consistency. If it spikes sporadically for a split second it needs a sensor.

Another thing to consider. You said this was a stock truck, I wonder if your EGR valve is malfunctioning or possibly the choke flap is giving you trouble.
 
#34 ·
That's a good point Lox.

One of the throttles for my EGR was getting stuck before I deleted, and the truck wasn't getting any air, so must have been the one in the elbow coming from the intercooler, but you could probably try unplugging it and going for a drive?

Will someone else confirm it won't just go into limp or low power mode?
 
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