6.4L Power Stroke Engine and DrivetrainDiscussion of the 6.4L Power Stroke diesel engine and drivetrain in the 2008 Super-Duty trucks. No gas engine discussion allowed except on transmissions and drivetrain that pertain to all models. Please confine discussion of topics in this forum to those items that are specific to the 6.4L Power Stroke engine.
My 6.4 is having a running issue that has been in the shop twice without any improvements on how the engine is performing. Anytime the engine is above 1800 to 1900 rpm, the boost gauge reads 20psi for a long period of time. I usually make 1000+ mile trips and this will happen for up to 500 miles at a time. In the rare occasion that the boost gauge reads 5 to 10 psi, the engine and fuel mileage is improved. When this does happen, it only lasts 15 to 20 minutes then its back to 20psi boost. The only thing I am hauling in the truck for now is 700 lbs of sandbags for traction in the snow. This would be my personal truck. My work truck is totally different in how it runs. It will run 5 to 10psi boost on the highway on level ground. The work truck is heavy (11,500+lbs) and still manages 14mpg on the highway. Any help would be appreciated. Thanks.
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Work:
2008 F-350 XL 6.4ltr 3.73 gears with a toolbox, Blue
Personal:
2008 F-350 Lariat 6.4ltr 4.30 gears Longbed Dualie Blue w/silver
Past Trucks:
2006 F-350 XL 6.0ltr with a toolbox, Blue - Drove 100k, only 1 breakdown, oil pump for injectors @97k
2001 F-350 XL 7.3ltr with a toolbox, White - 300k, bulletproof
I think that during the +20psi periods of time, this is normal operation. Under low boost conditions, you are in regen. But, your fuel mileage should decrease during the regens.
How do you drive the trucks? Mostly highway, city, etc?
The trucks are different.....The personal truck (dually) has 4.30 gears and the work truck has 3.73 gears. The higher the boost, the lower the mileage as expected. The strange thing about the dually is that the boost stays up in the 20psi range cruising down the highway anywhere from 55 to 75 mph. The fuel mileage will stay around 9.5mpg. Most of the driving with both trucks is highway. The work truck is doing 13.8 @ 80mph up here in beautiful sunny Wyoming. I just filled the work truck up and checked the mileage on paper.
__________________
Work:
2008 F-350 XL 6.4ltr 3.73 gears with a toolbox, Blue
Personal:
2008 F-350 Lariat 6.4ltr 4.30 gears Longbed Dualie Blue w/silver
Past Trucks:
2006 F-350 XL 6.0ltr with a toolbox, Blue - Drove 100k, only 1 breakdown, oil pump for injectors @97k
2001 F-350 XL 7.3ltr with a toolbox, White - 300k, bulletproof
Both tailpipes are clean. I agree about the gearing, so I have been matching RPM's on both trucks for a comparison. The dually is running slower and that should mean less load (wind).
__________________
Work:
2008 F-350 XL 6.4ltr 3.73 gears with a toolbox, Blue
Personal:
2008 F-350 Lariat 6.4ltr 4.30 gears Longbed Dualie Blue w/silver
Past Trucks:
2006 F-350 XL 6.0ltr with a toolbox, Blue - Drove 100k, only 1 breakdown, oil pump for injectors @97k
2001 F-350 XL 7.3ltr with a toolbox, White - 300k, bulletproof
Got my truck out of the shop and I thought I would pass this along just in case anyone else has this running problem.......The EBP (exhaust back pressure) sensor tube was carboned up. The fuel mileage went from 10.5 to 14.0 mpg at 70mph (verified on paper). It might be worth doing this at every 30k as a preventitive maintenance.
__________________
Work:
2008 F-350 XL 6.4ltr 3.73 gears with a toolbox, Blue
Personal:
2008 F-350 Lariat 6.4ltr 4.30 gears Longbed Dualie Blue w/silver
Past Trucks:
2006 F-350 XL 6.0ltr with a toolbox, Blue - Drove 100k, only 1 breakdown, oil pump for injectors @97k
2001 F-350 XL 7.3ltr with a toolbox, White - 300k, bulletproof
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Engine Running Issue - Any Ideas?
Linear Mode
