Problem with to much boost

[jeep91]

I recently installed a Spartan tuner with a cat/dpf delete on my job 1 F450 that has 16,000 miles on it. I have been running the 210hp tune around town and have no problems at all, it runs great and my mileage is about 25% better.

Last weekend I went on a 240 mile road trip towing my fifth wheel that weighs about 17,000lbs. I used the 75hp tune on the trip down (got 8.2mpg which is good for my truck) and had no issues with the exhaust temp.

So on the way home I wanted to try the 150hp tune to see if my mileage would be any better. It was doing fine but about 30 miles into the trip going up a hill I lost almost all power. The truck seemed to be running fine but when I would give it gas it would barley accelerate. I pulled over and shut the truck off then turned it back on and it seemed ok.

So after this the truck was making tons of boost still on the 150hp tune and my mileage dropped to 6.4mpg. I took it easy on the truck until I could pull over and switch tunes back to the 75hp since I didnt have any issues with that.

After I started on the freeway with the 75hp tune the boost would climb to 40psi and just stay there. I had the cruise on at 65mph about 2100rpm. I tried to go 70mph and it was the same thing, the boost would slowly climb to 40 and stay. Same at 60mph. Also when I would coast down a large hill and the truck would downshift to maintain speed it would still have 5lbs of boost, never would drop to 0.

I made it home getting around 6.7mpg going slower then I did on the way down. Does anybody have any ideas on what might be going on or what I might try to monitor?

Thanks.

[po-po 5.0]

These trucks aren't wastegated so the boost is....what the boost is. The only thing I could think of would be additional backpressure in the exhuast caused by a, possible, plugged DPF (which I don't think you have). Alternatively, its possible....though unlikely....that the variable vanes in the turbo are stuck closed?

[firemansdiesel]

Have you tried towing w/ the 210 tune? If so, did you lose power like the 150 & 75 tune? You are making good boost and it's not a turbo issue. Sounds like a fueling issue. May want to check your fuel and rail pressure and see what it is doing under load. Common rails can be finicky when turning up the hp.

Since you have no DPF on your truck (if I read that right) there is no play into that.

[jeep91]

I didnt want to tow that much weight with the 210 tune since I can get the EGT up with no load on that tune. I did watch the fuel rail pressure when I was having the problem, when crusing on the highway it would stay between 17000 and 21000. The truck is on its second high pressure fuel pump.

I loaded the 210 tune today, seems to be running fine but its still making about 5lbs of boost going down hill. After doing some reading I wondered if it could have something to do with the EGR valve being stuck.

[firemansdiesel]

It very well might be. Also you won't generate that much boost going down hill. Since momentum and less go peddle is applied.