So I've been having a overboosting problem since I picked up my Excursion about a year ago. I've cleaned the EBPS tube and replaced the sensor. Replaced the MAP sensor, hose and cleaned out the nipple. Installed a new stock turbo with the VGT solonoid and still it's overboosting. First gear through third it sits right at 26ish psi and then fourth it jumps up to around 30ish maybe a bit higher then in fifth it will climb up to 34 psi. This is not pulling either. It's worse with a load behind. At this point I'm ready to buy studs and gaskets because I'm sure it's coming. Man I don't want to do head gaskets. If anybody could help me I would be so great full.

 

Any tuning done?

Sounds like maybe vanes are sticking, but it's a new turbo, right? New solenoid, too?

 

Yes I'm running a canned SCT tow tune. Mildest one I can find. Mainly bought it to get rid of the CEL light after my EGR delete. And yes it very much seems like sticking vanes but after cleaning the old turbo which didn't help and just now installing a brand new not rebuilt turbo with a new solonoid and still getting the same results I'm getting really bummed out. I should mention it has a aftermarket exhaust system. From the turbo back with a Cat delete. Just a aftermarket 4" muffler.

 

Also I should mention it doesn't have the whistle a idle like other 6.0l I've heard, just a deeper rumble. Thought maybe it did when I first got it but for sure not now. Should I be doing the VGT relearn? Do I need to return to my stock tune to do so? Thanks

 

So here's me thinking. What if my throttle plates are some how closing off at higher speeds? The boost gauge is tied into the tube before the plates. Or maybe the gauge is dickered? I'm going to rig up another one and try it anyways.

 

Where and how ard you reading boost? Are you getting over boost codes? Some scanners will read PSIA insted of PSIG and that will make you about 15 lbs off

 

I have a auto meter mechanical gauge on my pillar. And it set the P0299 over boost code once last summer while pulling our camper.

 

The only other thing I can think of is I'm pretty sure I have a small exhaust leak on one of my up pipe bellows. Around 20psi (depending on engine temp) I get a kettle type whistling.

 

Take the tune out and see what it does.

 

Yes I'm going to try that and a VGT relearn tonight. Can I shut off my EGR and run a stock tune with a SCT tuner?

 

Just return it to stock with the sct. You may have a cel for the egr but that's fine until the boost gets figured out

 

Sounds like you need more data points to nail down. As many have noted here on the forum in the past, what's your EBP, MAP, and Baro at koeo?
Somehow, your PCM/ECU is getting incorrect data to activate that turbo.
Can you measure your vgt's to see what info its sending your turbo?

 

Yes for sure. My dash boss was dicking me around last night but I'll get some numbers tonight. You want key on engine off and running? Thank you.

 

If your running a throttle plate, remove the butterfly flapper on the shaft, that will remove the restriction. Leave the shaft alone and the throttle plate hooked up electronically.

 

Yes for sure. This is good lots of things to try tonight. Thanks again.