I removed the turbo last week and performed the cleaning procedure. that part went fine and i replaced the unison ring while i had it apart.
seemed to be fine all week,then tonight it began doing what it was doing before all this. When i started it up I could tell from the sound of the exhaust that it would't be boosting up when i drove away. boost stays around nothing. if i get on the gas hard, it'll boost up. as i let off the boost gauge will drop to nothing.
would a bad VGT solenoid cause this?
any way to tell if it's the solenoid?

thanks.

 

First things first have you checked for codes? Next you should should go through the low power checklist in the tech folder at the top of this forum. My bets on a plugged up egr valve it can feel like you have no boost in the low rpms. Vgt's can fail but are not to common.

 

It might simply be the VGT solenoid pigtail broken and the vanes on the turbo are at default position. You'll get a lot of boost but it will be laggy and have high EGT's on low end. It usually throws a code but no CEL.

 

Okay, I pulled the codes and here they are:

P0069 - MAP Baro pressure correlation
P0096 - Intake air temp sensor 2 circuit performance
P0299 - Underboost
P0470 - Exhaust pressure sensor circuit
P1408 - EGR flow out of range

Here are the details of the truck and what I've checked and done so far:

2005 F250, EGR delete, 4" MBRP catback. The rest is stock.

New FICM installed in December. Got home and checked their work and EBP sensor was disconnected. Not sure why this was disconnected for a FICM job. Whatever. This could have thrown the P0470 code.

Around this time, I began having underboost/overboost symptoms. did the turbo clean up procedure. Put in new unison ring because mine was a little worn at the bottom of the slot.

Last night I removed the EBP tube and cleaned it. It was gummed up but not clogged. Also checked the MAP tube. I suppose I could replace both of these sensors.

last night I unplugged the VGT solenoid and drove it around the block. With it unplugged, it's identical to whatever is causing it to not boost like it did last friday night. Plugged in it boosts up as needed. However, when it's sitting there idling I can't tell a difference in sound when the VGT is plugged or unplugged.

It hasn't acted up since Friday, so whatever's wrong it seems intermittent.

I'm open to ideas. Thanks.

 

I am working similar problem and diggin deep into the forum, did you get it figured out? what helped, thanks.

 

Carolina, did you pull the EGR valve and clean it?

 

A new EBP sensor fixed the issue.

My EGR cooler is deleted. The valve itself is clean (relatively speaking).

 

How much do they get for a new ebp sensor ?

 

anywhere from $70 - 100.

I think I paid about $90 when I picked one up at my local ford dealer.

This site has good prices on stuff too:

[DPFE-6]Motorcraft Exhaust Back Pressure Sensor(EBP)-DPFE6-Ford Diesel Trucks - Diesel Filters,Additives,brake rotors, and brake pads for Chevy, Dodge and Ford Diesel Trucks

 

Thanks for the info, that may be a good less costly route to go before replacing the turbo.

 

had a similar issue turned out to be a loose VGT solonoid pigtail
one of the plastic hooks was missing sometines the truck worked great
then it didn,t
repaced it with a pigtail from the ICP valve ( it has a metal spring holdover thing ) truck works ok

 

CDEV you must have been reading my mind!! just got done checkin wires and sure enough BOTH clips are broken off. was gonna try some safety wire to hold on tight. Why did you use icp pigtail instaed of new solenoid version?