13lbs of boost, then zero

[dmd]

Short story - when boost hits 13lbs I hear a woosh noise and boost drops
to zero. Letting off the peddle some (or all the way) and the boost returns. I can
repeat it at will. Does the same on cruse control.

Long story-

-Stock except for in-tank and pre-pump mods, gauges too
- happens at any RPM 2500-2800 (need that rpm to get that boost)
- When boost is at zero, engine is still pulling but not very strong
- EGT goes over 1000deg (post turbo) real fast once the boost is gone and
keeping the peddle to the floor or the cruse is engauged
- Runs great until boost gets to 13lbs
- Slight woosh noise when boost is lost (hard to hear because of normal
engine noise at that RPM
- if I let off some, not even all the way, I get boost back (untill it reaches 13lbs)
- allowing the trans to shift will get the boost back (have to let off the peddle some
to get it to shift (probably same as above).
- changed pre-pump filter after it first happened, engine fuel filter was changed
about 4k ago ( I believe it is getting fuel from the high EGT when no boost)
- Can repeat at will, easier with trailer attached
- Can repeat with fuel peddle or using cruse control
- Keeping boost below 13lbs and engine runs fine, slow up hills when pulling though
- no change in milage
- not sure when it started, but just noticed it when pulling this weekend


Ideas & solutions??

To me the symptoms sound like a waste gate issue, but not sure what needs
fixing....

 

[Tbar]

Sounds like you have a loose intercooler boot/clamp.

Check the two on the intercooler............two on top of the y pipe and one under the y pipe.


Tbar

 

[dmd]

Sounds like you have a loose intercooler boot/clamp.

Check the two on the intercooler............two on top of the y pipe and one under the y pipe.


Tbar

I checked the boots and didnt see any movement. Could the boots blow off
and then be able to seat well enough to take 12-lbs of boost over and
over? I though that once they blew off they would just be off.. Please
correct me if I am wrong here.

 

[bushpilot]

maybe a torn or LEAKING boot that doesnt "leak" until 12.1psi...

 

[Zookie400]

if a boot blows off, it stays off. if a boot were to leak, it would leak and you would see a low boost number, but it wouldnt dump pressure.

sounds to me like this is a problem with the confuser defueling due to something.....have you checked for faults?

it could also be a problem with the wastegate...in some wierd manner. try disabling the wastegate (i prefer the zip tie a kink in the signal hose method) and going for a quick ride.

 

[BIG JOE]

What Tbar & BP sez. You could remove all yer I/C & intake boots.. clean'm up real good and inspect them All for cracks or pin holes. If they're the origionals, you might think about replacing them all. They seldom rupture but do leak, under pressure. Not that expensive to do.

Joe


Hint: Use Windex to replace or re-install.

 

[dmd]

if a boot blows off, it stays off. if a boot were to leak, it would leak and you would see a low boost number, but it wouldnt dump pressure.

sounds to me like this is a problem with the confuser defueling due to something.....have you checked for faults?

it could also be a problem with the wastegate...in some wierd manner. try disabling the wastegate (i prefer the zip tie a kink in the signal hose method) and going for a quick ride.

Is the signal hose the one that goes to the MAP sensor? Probably the hose
that I have my boost gauge in that goes from the "Y"and runs left
to a little module?


I will test that and then get the codes read... Do I need to buy a tool
for this or are there places that I can get it read??

 

[DaveBen]

You will need to find someone who can read Ford CAN code protocol. Auto Xray and Autoenginuity both can read our trucks, but Autozone CANNOT read our trucks.

Dave

 

[dmd]

You will need to find someone who can read Ford CAN code protocol. Auto Xray and Autoenginuity both can read our trucks, but Autozone CANNOT read our trucks.

Dave

Know of anyone in the DFW (texas) area that has one?

 

[Zookie400]

im not 100% with superduties, so someone who knows better should chime in....but i know just about everything else i work on will have a small hose that runs from the compressor side of the turbo to the wastegate actuator. that is the hose you want to kink (or remove and plug) and go for a quick ride.

a lot of slip seat drivers do this to thier rigs because it lets the turbo overboost and they get more power....then a month later, when they are long gone from the truck, the turbo shreds itself, or smokes the bearings and comes in to see me. for a quick test drive its ok though.