I have 2005 F250 6.0. Recently I had my Y Pipe crack at one of the flex joints (naturally). I had to remove the turbo for the install. Once the install was complete I took it for a test drive, as soon as I pulled out on the road I noticed my truck would not exceed 6lbs of boost… I was a little confused because with the leak in the old pipe I was running about 22+ lbs. So the investigation begins… while I was removing the turbo I noticed the pig tail leading to my turbo actuator was looking a little rough so I replaced, unfortunately didn’t change anything.. I had to let the truck sit for a week due to my work schedule but now I need to dig back into it. When I started it up it took a minute for the turbo to spool but once it did felt like there may be an air leak but I just put a new T pipe in and the other down pipe going into the EGR was replaced not even a year ago. I do have an EGR delete As I started doing my research I came across many different things that may cause my turbo not to exceed 6lbs of boost.. It could be the turbo actuator, exhaust back pressure sensor needs cleaned or just cleaning the turbo or many other things. But here is where I am scratching my head!... There was no problem with the turbo before I did the pipe install, it doesn’t make sense to me that any of those possible problems could be my issue.. Did it just happen over night without the truck even running because prior to the install everything was operational. I have guy I know with a high quality scanner but he wont be back in town for 2 weeks, Unfortunately I have to figure it out ASAP.. Before I dump even more money into this truck I decided I was going to go back through and remove turbo and go through my pipe install to ensure myself that it couldn’t be it.. I did unhook the batteries during initial pipe install, Is there a VGT relearning process As I just removed my turbo can ANYBODY please give me some direction or advice when it comes to the process of elimination when seeking to find the cause of my problem here….Anything helps guys. Your thoughts and suggestions are very much appreciated. Thanks

 

There is a VGT relearning process but I don't believe it would cause boost to be limited to 6 psi. See it here.

It's extremely important that the up-pipe be seated perfectly on the turbo. Even an 1/8" gap will leak. You can't use the clamp to pull them together. And then there's the EGR cooler to pipe connection that requires the use of a gasket. There's also another connection point that requires a gasket but I don't remember exactly where.

I would double check each of the up-pipe connections and make sure there's absolutely no gaps. I'd also make sure that your MAP hose is plugged in to the map sensor and on the nipple on the intake and that the hose has no cracks. No MAP signal would cause turbo issues. Also double check each CAC tube boot for pinholes or rips, cracks, tears. And then I'd try the VGT relearn procedure.

 

Thank you so much for your input!! I will be sure to cover every aspect of your post. I will keep you update as I'm digging into as we speak. Thanks again

 

By chance the flange on the up pipe at the connect point, does that flange need to be bent on locking it on the turbo then tighten clamp to finale seat it or do I tighten clamp and disregard clamp?

 

All of the exhaust flanges need to mate up flush/square to each other. The clamp will not pull it in place to seal properly.

 

This is just an idea of what could be wrong. Recently I removed my turbo to get to my HPOP and I decided to split the turbo open to see its condition. As it turned out, my unison ring and veins were all rusted and frozen together. So during operation the unison ring would not rotate which controls the gap openings between the veins. In addition to loss of performance, I've heard that a seized up turbo can lead to head gasket failure. I did not take the turbo completely apart. After a few hours of some polishing and light greasing the turbo's unison ring and veins now move freely.

 

So Yesterday I
removed the turbo to replace all exhaust gaskets and check for any leaks. The Reinstallation went very smooth, everything slid right into place and clamped everything back in. Couldn't of felt more confident. Took the truck for a test drive, wouldn't push over 3lbs of boost, Before I was at 6lbs of boost so things are getting worse. So I removed the turbo again to check all my flex joints in pipes and I noticed some build up on the outside of turbo, took wire wheel and cleaned it all up.. flex joints are good so now the turbo is back in and went for a drive... little to no boost.. feel like I may need to pull turbo apart or go get it scanned? thoughts?

 

So Yesterday I removed the turbo to replace all exhaust gaskets and check for any leaks. The Reinstallation went very smooth, everything slid right into place and clamped everything back in. Couldn't of felt more confident. Took the truck for a test drive, wouldn't push over 3lbs of boost, Before I was at 6lbs of boost so things are getting worse. So I removed the turbo again to check all my flex joints in pipes and I noticed some build up on the outside of turbo, took wire wheel and cleaned it all up.. flex joints are good so now the turbo is back in and went for a drive... little to no boost.. feel like I may need to pull turbo apart or go get it scanned? thoughts?

 

You plugged the VGT connector back in on the turbo, right?

 

Yes I did. I have nor done the relearning process yet as I was suggested. The truck has 235k miles the turbo might need replaced or cleaning. gonna crack it open today

 

Just checking. Seen it happen...

I would open it and see if the ring is stuck.

 

with that mileage im willing to bet that it needs a good cleaning.
maybe replacing. send us some pictures of it once you get it apart.