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What is going on with my engine?

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Oil pressure help

Bad negative battery cable

'07 5.9, g56, bone stock setup w/ gauges.
So, I've been trying to chase down a boost issue for a while now. Initially replaced a leaky boost hose and added an autometer boost gauge w/ boost bolt in the intake. When I drive, I'm only reading ~4-8 psi unless I punch it going uphill which will get me to about 14 psi. Everywhere I read, people are saying these trucks make ~30 psi at WOT and I can't even get near that. I verified the boost pressure by checking against the MAP reading on my scan tool as well. Today I connected my boost leak tester again to try and find the culprit. while I was underneath my truck trying to get a better view of my wastegate, I could hear a slow hissing sound coming from my oil pan. sure enough, I pop my oil fill cap off and hear/feel a small hiss of air. the weird thing is, when I start the truck and try and hit the accelerator with the cap off, there's nothing, not a hint of blow-by. Can anyone help me figure out whats going on here I'm at a loss?
 
I could hear a slow hissing sound coming from my oil pan. sure enough, I pop my oil fill cap off and hear/feel a small hiss of air.

Not sure exactly how you are doing your boost leak test, but if you are pressurizing the intake system, then it would be normal to hear air passing around the piston rings of the cylinder that had an intake valve open.

- John
 
Broken Wastegate Solenoid, now it only goes to preset value.
Very typical the problem you describe.
99% sure its this, you'll be amazed how much better that Truck goes with doubled boost pressure.

Seen 4-8 on flat land is common, even 0 is possible.
28-30 at WOT is standard.

PS: i had exactly the same on my truck when i bought it, found it like you with the added boost gauge.
 
Fist thing to do is crimp the boost reference hose on the front of the turbo shut and test again. If you cannot make mid 30's boost and set a CEL turbo is a candidate for problems.

Assume you did not find an boost leak, if you did not block the CAC tube at the intake elbow it was just bleeding pressure thru an open valve and the rings. Normal.
 
Mine delivered ~14psi with the dead Solenoid. Almost exact half of the desired value.
Maybe there are different versions out there. Or mine just had a glitch.
 
Broken Wastegate Solenoid, now it only goes to preset value.
Very typical the problem you describe.
99% sure its this, you'll be amazed how much better that Truck goes with doubled boost pressure.

Seen 4-8 on flat land is common, even 0 is possible.
28-30 at WOT is standard.

PS: i had exactly the same on my truck when i bought it, found it like you with the added boost gauge.
Would a broken WG solenoid not pop a CEL? If I unplug it I get a CEL so that would make me think a broken solenoid would do the same
 
My understanding is that the WG is the same from 03-07, just the 04.5-07 have the solenoid controlling the airflow to the WG.

In playing with tuning of the WG solenoid I’ve never seen the WG open below 23, even with the solenoid wide open.
 
Would a broken WG solenoid not pop a CEL?

It should, but these early CAN systems had some glitches. Could be the WG actuator is bad and that is what is causing the issue, crimping the boost reference hose closed will pull all boost from the actuator so a broken spring will not open the WG too soon. If boost goes up but not to low to mid 30's at WOT, problem with either the WG or turbo.
 
Cool, I'll crimp it off today and see if that's the issue. Fingers crossed, because I'd rather replace a solenoid than rebuild a turbo or, God forbid, buy a new one
 
I don't think the turbo is bad, these older unit fail rarely, not like the first VGTs afterwards.
Fingers crossed for nice boost crimped.
 
Its actually a china knockoff lol. The guy I bought the truck from took the original Holset from this truck to put on another. But I checked the axial/radial play recently and it was all within Holset spec and nothing is leading me to believe that the turbo itself is bad.
 
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