Intermitant lack of power - no DTC's

[TimB]

2008 F-450 95500 miles.No DTC's. While driving it will intermitanly lose power when accelerating. Seems worse at highway speeds. When it happens MGP will start to fall. Will build 28psi boost then it starts dropping down to 10psi while APP is still at 99.5%. In the beginning fuel pressure was low and I replaced the fuel filters. Pressure was still low so i replaced the fuel pump. Now fuel pressure is normal but concern is still present. Also has new turbos. Attempted to check for boost leak but not seeing any leaks with smoke machine. Any help or suggestions would be appreciated.

 

Baro - 14.2

APP - 99.5%

DPF - 2.83 psi

EBP_a - 38 psi

EBP DSD - 24 PSI

EGRPCT - 0%

EGRT_A - 1.23k

EGRT_B 181

FLI - 24%

FRP - 23769 PSI

FRP_DSD 23736 PSI

FRT 107

MAF - 286 g/s

MAP - 28 PSI

MGP - 13 PSI

VGTDC - 36%

VGT MES - 37%

VSS - 64 MPH

[ktmlew]

I'll be watching this post as I have zero experience/training on the 6.4. But just looking at those PIDS the EBP_a 38 PSI looks high to me?

 

But again I have zero training on these.

[TimB]

Hotline says my FRT is to high. But i have compared that pid to a truck with no issues and it was at 100 degrees

[TimB]

I looked at some of my recordings, I did notice FRT going as high as 117 degrees, seems like if temp was under 105 degrees it was running better. Hotline says normal FRT should be 67-71.

[mchan68]

I have limited experience with 6.4s too, since I see very few of them in for any major driveability issues, but looking through the PC/ED, I see that reference values specify the range Hotline is telling you. I also vaguely recall that if FRT goes up to a certain, the engine WILL derate, but at what exact temperature escapes me. If FRT were actually an issue in your case, I would think a DTC would have been set.

[Keith Browning]

I agree with Mike but we all have seen things happen and not leave a code. Considering that FRT could be the problem I would spend a little time looking at the fuel cooler system. checking coolant level first. Check the service history to see if the system has been open recently which might have created an air lock - the purge procedure would eliminate that. Then I might look at the hoses and the fuel cooler pump. I have replaced a few pumps but they usually leave a circuit code... however the lack of a code won't necessarily rule out a blocked or damaged pump.

[TimB]

Hotline recommended following pinpoint test MC, but of course that leads me to replacing the PCM because the test never considers a problem with the cooling system. The fluid level is full, and the pump does come on when commanded. I disconnected one of the hose coming from the coolant pump and the flow/pressure seems week, but I dont have another vehicle to compare it to right now.

[ktmlew]

The coffee table book says this:

 

Quote:

Fuel returning from the pressure regulator on the engine mounted fuel filter comes into the HFCM and a DTRM

either allows the fuel to return to the tank or returns it

to the unfiltered side of the fuel filter in the HFCM. The

DTRM starts to open (recirculating fuel back into the

pump) at 80°F (27°C) and is fully open at 50°F (10°C).

 

I assume they screwed-up that last sentance and it starts opening at 50F and is fully open at 80F? Or maybe i'm just not getting it...

[mchan68]

Well, another simple test would be to read ALL temperature sensor PIDs at KOEO after cold soak wouldn't it? I would think they ALL should read equal to each other within a degree or two if fuel temperature really is in fact what's in question.

[Mikill]

Sounds like a faulty hp fuel pump. Quick test is to get vehicle to operating temp then rev to 2500 rpm for a min or two let it drop to idle and then immediately rev back up to 2500 rpm. If vehicle starts surging then the HPFP is sticking. They usually set the P0088 code but I have had a few with no codes present.