Turbo Problem

[PSD POWER007]

Alright Bush, here's the deal. I went on a towing trip to Knoxville, TN this week. About 350 or so miles one way. I was amazed at the difference in power. It was like driving a new truck. I set the cruise on 80mph and rode out. I hardly EVER went over 20psi while cruising. Even going up hills at those speeds. My milege went from 9.5 mpg to 11.6 mpg. I was absolutley tickled. No turbo problem what so ever. So I finished my job up there and headed home. All was well for the first 2.5 hours of the trip. Then suddenly, I felt a bit of sluggishness in the truck going up a hill at 80mph. (all of this trip was on the interstate) Looked at the Attitude monitor and I was up to 26psi. Then I got over the hill (and I mean just your standard interstate grade hill here too) and leveled off then started up the next hill and bam...low boost and high EGT's. It did this only once more on the way home. (last 2.5 hours of the trip) My mileage went from 11.6 mpg to 9.9mpg.
I got home and let the truck cool down. I went and pulled the EGR to see if the o-rings had torn or burned or something and all was fine. Do I dare go buy a $200 EGR valve or is there some way to test this one? I'm dumbfounded at this point.

 

[Kleetus]

You can find them on ebay for much less than $200.

 

[PSD POWER007]

I just don't wont to pony up the money if it wont fix anything. Trying to make sure first.

 

[bushpilot]

heres a good description about the turbo & vgt solenoid.

The EVRT (Electronic Variable Response Turbocharger) is also
known as a VGT or variable geometry turbocharger. It improves
upon turbocharger design by changing the size of the vanes in
the turbine housing, allowing control of boost by controlling
exhaust turbine inlet pressure.

The size of vanes changes positively as engine speed increases.
At low engine speeds, the increased pressure generates higher
boost than traditional turbine design.

The Garrett turbocharger changes exhaust air pressure by using
piston to rotate a cam that rotates a unison ring which pivots the vanes.

Pivoting these vanes controls the size of the opening between the
vanes thus controlling the pressure of the exhaust gasses in the
turbine housing...

The position of the vanes will determine whether a low boost or
an over boost condition occur..


dont buy that egr replacement YET...next time you have this problem...
pull over, shut the truck down (completely)...disconnect the egr and
then resume driving...see if you have the problem (drive awhile to
see if you have the problem or the problem comes back).

over boosting could be a sign that the VGT solenoid could perhaps not
be working....it could also be a sign of sticking vanes.

boost is controlled by the vgt solenoid and the vgt vanes...the vgt
solenoid is the piston that makes the vgt vanes open and close.

the VGT Solenoid could be command <improperly> to open or shut the
vanes if the EGR valve was not working properly...the egr valve, ebp
and the vgt all work together...so if ONE is not working "right" or
producing the EXPECTED results (after the computers command it
to work) other devices will also work improperly or be commanded
to work in a way that may produce "ill" results.

its a twisted web...but and things work in unison...so disconnecting
or blocking one item MAY have results <desired or not> on another
"object"

what engine codes do you have set ? if youre running a tuner
id recommend that you drive w/OUT it for awhile just to
make sure its not the problem.

i dont know how your tuner works but most work by increasing
the fuel <amount> and pressure...which COULD increase the risk
of soot-ing up the VGT vanes...