I have a 2008 peterbilt 389 with the single valve cover cat.
Engine came factory with twins and actuators and DPF filters of course....
It's haunted.
Looking for a guru....
Please read entire post before suggesting a fix.... as I will tell the whole story and what I have done thus far.
About six months ago the truck started vibrating/sputtering like it needed a fuel filter.
So I stopped and changed filters. It seemed to have fixed it. Until about 20 miles down the road it started sputtering again.
It continued like this until I got it back home. If you ask the truck for full throttle for too long it will start missing/sputtering etc....
It feels EXACTLY like a fuel filter.
So the first thing I did was replace the fuel lines.
Then I changed the draw tubes.
Then I put a new fuel pump.
Then I replaced the fuel pressure valve and the check valve in the filter housing.
Then I thought maybe air was getting back in the fuel so I replaced all the injector o rings.
Then I bought two new injectors and replaced #2 and #4
Then I swapped them to #5 and #6
Then finally I swapped them to #1 and #3
Nothing has changed at all.
The truck is fully deleted, and is set somewhere around 600-650hp
No DPF no intake actuators.
The truck acts the same every time, and is extremely consistent.
When you leave the house for the first time the truck will build 50-55 pounds of manifold pressure, and smoke slightly at full fuel.
After about 5 miles the truck will only make about 38-40 pounds of manifold pressure and no smoke.
That is the first step....
After the initial loss of power the truck will run that way for the rest of the day, unless you ask for full throttle for too long.
If you stay in it while pulling a long hill or if you run 75-80 mph for longer than a few miles then the truck will begin missing/vibrating/sputtering/etc... and will only make about 28 pounds of manifold pressure.
Once it does that if you keep your foot in it it will sputter all the way to Mexico. But if you let off and let it coast for a while it will come back and be the 38-40 pound truck again and run smooth. But will only go back to being the 55-60 pound truck if it is left at an idle for a while.
Like I said it is extremely consistent, which is what made me think it was gradual loss of fuel pressure... but the truck maintains 90 pounds of fuel pressure at every stage of its horsepower. Fuel pressure NEVER drops. That's with a manual gauge hooked to stratoflex at the fuel filter port.
The last piece of the puzzle I have will be for someone who has more knowledge than I do.
I hooked it to my laptop the other night.
While looking through different things in ET I saw something that said fuel delivery rate. And also something that said engine derate percentage.
My mechanic kept an eye on these two things while I held the truck at full throttle.
The engine derate percentage never changes. The engine IS NOT derating.
The fuel delivery when I first crank the truck is 585mm of fuel when held at full throttle. The truck will make 55 pounds of manifold pressure there.
When the truck falls to 40 pounds of manifold pressure the fuel delivery is showing to be around 480mm of fuel.
Any suggestions would be greatly appreciated.
Is a turbo failing? Causing air loss which translates to fuel cut back?
Or is there another fuel problem I could have?
6 months of hard searching and I finally need help.
Thanks for having me
Engine came factory with twins and actuators and DPF filters of course....
It's haunted.
Looking for a guru....
Please read entire post before suggesting a fix.... as I will tell the whole story and what I have done thus far.
About six months ago the truck started vibrating/sputtering like it needed a fuel filter.
So I stopped and changed filters. It seemed to have fixed it. Until about 20 miles down the road it started sputtering again.
It continued like this until I got it back home. If you ask the truck for full throttle for too long it will start missing/sputtering etc....
It feels EXACTLY like a fuel filter.
So the first thing I did was replace the fuel lines.
Then I changed the draw tubes.
Then I put a new fuel pump.
Then I replaced the fuel pressure valve and the check valve in the filter housing.
Then I thought maybe air was getting back in the fuel so I replaced all the injector o rings.
Then I bought two new injectors and replaced #2 and #4
Then I swapped them to #5 and #6
Then finally I swapped them to #1 and #3
Nothing has changed at all.
The truck is fully deleted, and is set somewhere around 600-650hp
No DPF no intake actuators.
The truck acts the same every time, and is extremely consistent.
When you leave the house for the first time the truck will build 50-55 pounds of manifold pressure, and smoke slightly at full fuel.
After about 5 miles the truck will only make about 38-40 pounds of manifold pressure and no smoke.
That is the first step....
After the initial loss of power the truck will run that way for the rest of the day, unless you ask for full throttle for too long.
If you stay in it while pulling a long hill or if you run 75-80 mph for longer than a few miles then the truck will begin missing/vibrating/sputtering/etc... and will only make about 28 pounds of manifold pressure.
Once it does that if you keep your foot in it it will sputter all the way to Mexico. But if you let off and let it coast for a while it will come back and be the 38-40 pound truck again and run smooth. But will only go back to being the 55-60 pound truck if it is left at an idle for a while.
Like I said it is extremely consistent, which is what made me think it was gradual loss of fuel pressure... but the truck maintains 90 pounds of fuel pressure at every stage of its horsepower. Fuel pressure NEVER drops. That's with a manual gauge hooked to stratoflex at the fuel filter port.
The last piece of the puzzle I have will be for someone who has more knowledge than I do.
I hooked it to my laptop the other night.
While looking through different things in ET I saw something that said fuel delivery rate. And also something that said engine derate percentage.
My mechanic kept an eye on these two things while I held the truck at full throttle.
The engine derate percentage never changes. The engine IS NOT derating.
The fuel delivery when I first crank the truck is 585mm of fuel when held at full throttle. The truck will make 55 pounds of manifold pressure there.
When the truck falls to 40 pounds of manifold pressure the fuel delivery is showing to be around 480mm of fuel.
Any suggestions would be greatly appreciated.
Is a turbo failing? Causing air loss which translates to fuel cut back?
Or is there another fuel problem I could have?
6 months of hard searching and I finally need help.
Thanks for having me
