2005 LBZ losing power

[sik 07]

My buddy has a 2005 LBZ and it has been losing power at about mid throttle. It seems to go into a limp mode but does not have a CEL. When he goes about 65 MPH and steps on the throttle slowly it'll power down to about 45 MPH. The truck will stay there for a while and will eventually be able to get speed again but usually does it again on a grade. That was with the truck empty. Any help on figuring this problem out is greatly appreciated.

 

[Bdsankey]

What is fuel quantity doing? IE is the desired fuel quantity dropping? How is desired vs actual rail pressure? Is that being commanded down as well? What is boost doing? Is TPS constant?

 

[dndj]

How long since the last fuel filter change?

 

[Dkatubi06]

Fuel filter plugged

 

[JoshH]

Just so we are clear on what kind of truck is being discussed here: 2005 model year would be an LLY; it would have to be a 2006-7 to be an LBZ. You're going to need to hook up a scan tool of some sort to see what is going on, but I would certainly lean toward a fuel supply issue.

 

[KyleC4]

Does this concern happen all the time or just when your buddy’s truck is almost on E ? That’ll help too.

Sorry misunderstood empty as being truck unloaded. Not fuel quantity

 

[sik 07]

So not too sure when he last changed the fuel filter. The truck was full of fuel when it slowed down. No check engine light on. Empty meaning unloaded. I'll ask him when he did his last filter and have him take it for a scan.
Thanks for the input.