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James
James, Ford Technician
Category: Ford
Satisfied Customers: 3588
Experience:  Ford Senior Master Tech, Ford gas and diesel expert, ASE Certified
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I have a 2008 6.4 diesel. When the truck gets to 50mph, it

Customer Question

I have a 2008 6.4 diesel. When the truck gets to 50mph, it loses power and boost drops off. I just replaced both turbos, and low pressure fuel pump. EBP is 16psi at idle and around 50psi at WOT.
Submitted: 1 year ago.
Category: Ford
Expert:  James replied 1 year ago.

Hello, when you lose power do any warning lights come on?

Customer: replied 1 year ago.
No, no codes at all.
Expert:  James replied 1 year ago.

What does your boost drop down too? What is the current temp outside?

Customer: replied 1 year ago.
As soon as the truck loses power the boost drops off. If you go from a dead stop and floor it, the truck takes off and has plenty of power. As soon as you get hit 50mph, the boost drops off to about 15psi and the truck slows down.
Customer: replied 1 year ago.
65*
Expert:  James replied 1 year ago.

I'm going to guess the fuel level isn't low? No abnormal noises just no power? No codes stored in memory without a check engine light? A faulty EGR valve could cause this similar issue.

Customer: replied 1 year ago.
Truck is full of fuel. It has a brand new EGR valve as well. No codes stored or check engine lights.
Expert:  James replied 1 year ago.

Do you hear a loud air leak by chance? I would visually inspect the CAC tubes for a leak. Are they ok?

Customer: replied 1 year ago.
No boost leaks. I have checked all the intercooler hoses.
Expert:  James replied 1 year ago.

Does this have a programmer installed by chance?

Customer: replied 1 year ago.
Bone stock truck. No tuners or deletes. 2wd dually with a service bed.
Expert:  James replied 1 year ago.

This is a hard without a code to go off of. It sounds like the vehicle needs to have data watched in order to diagnose. If the thermostat is opening to soon it can affect engine operation. Another thing is the EGR valve is opening or sticking open you can have this issue.

Customer: replied 1 year ago.
Thermostat is opening as it should. The EGR valve is brand new Ford piece. I just put it on 2 days ago.
Expert:  James replied 1 year ago.

The VGT may not be working correctly. Can you monitor data.

Customer: replied 12 months ago.
it seems to be working fine.
Expert:  James replied 12 months ago.

How did you test it?

Customer: replied 12 months ago.
I have a Auto Enginuity scanner, I can monitor what it does.
Expert:  James replied 12 months ago.

If all of those items are ok I suspect you have a fuel related concern. If there is an issue or a calibration issue in the PCM you can have these concerns.

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