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Discussion Starter #1
So I finally got my tuck back together and running this weekend after having it torn apart for over a week doing an EGR delete, oil cooler swap, and tracking down an HPOP leak which turned out to be the STC fitting.

I got it fired up, and it ran great!!

BUT....now, just when I think I'm out of the woods with this thing...it's having another issue. A couple times over the weekend after I would fire the truck up, I noticed it had ZERO power.....just about nothing there, and even with the pedal to the floor, it was making ZERO boost. The couple times that it did this, it might have done it for 30 seconds, up to a few minutes.......and then all of a sudden, it was like someone flipped a switch and the turbo spooled up and come to life, and the next thing you know it's making 28psi of boost and pulling like it should.

After every time I had that no boost issue, after I got home I scanned the PCM and found a P0299 "turbo underboost" code.

Does this sound like a sticky unison ring, a VGT solenoid issue, or maybe something going on with the EGR valve? (I did the delete, but left the valve plugged in and in the intake)? Could it be a wiring issue? The plug going to the VGT solenoid looks pretty crummy, along with the wiring going to it.

Later tonight it started doing again at my house, and I never did get it to make boost....I was so frustrated, I just parked it in the shop.

Just looking for ideas here, and where to start my troubleshooting!!
 

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The VGR pigtail can be a problem, as can the VGR itself. Do you have a reader that can command the VGR open or closed like AE and read its status? Has the unison ring ever been cleaned or replaced?
 

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Discussion Starter #3
I have a way to monitor all of the PID's, but the software doesn't have the ability to command anything.

I just got the truck about a month ago, not sure if the unison ring as ever been cleaned....but everything seemed to work good before I torn everything down recently to do the EGR delete, oil cooler, and STC fitting update.

It's strange that one minute there is no boost....then all of a sudden it's spooling up and making boost. Something is not right.

I'm sure it's either a sticky unison ring, vgt solenoid, ebp sensor.......or maybe a wiring issue?? I will fire it up today after work and get some data I will post on what the different sensors are reading.
 

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Try the easiest thing first. Replace the pigtail. If that doesn't work you can move on from there. Sounds like it needs to be replaced anyway.
 

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Discussion Starter #5
***UPDATE***

OK.....here is what I found out.....it just confuses me more. Maybe it IS the EBP sensor??

So I went out to the shop and turned the key on and let my Torque App on my phone sync with the bluetooth ODBIII dongle so I could read all of the PID's.

With key on, engine off.....here is what I'm getting. MAP: .1, EBP 14.2, VGT 0.0, and I was showing a P0299 (turbo underboost) and P2262 (turbo boost not detected) faults.

I fired up the truck, it started right up......but instantly I noticed that I didn't have that typical turbo whistle coming from the exhaust....it just sounded rumbly, with no turbo whistle at all. I fiddled around around with the EGR and VGT plugs while it was idling....no change. Went around and moved all of the wiring around....no change.

With the engine cold and idling....this is what I got. MAP: -.1, EBP was at 40 but then dropped to around 15, VGT was up at 85% (which it always does since I don't have a muffler or cat).

So I let it warm up, and took it for a drive. Same as before. NO power, I could only get around 10psi MAP (boost), and the VGT was moving around between 40-60%. NO power, and just a hint of turbo wine. It wasn't blowing any white or black smoke...just no power. The one strange thing I noticed is that the gauge on the dash stayed about at 0-1, even with the MAP was at 10psi....strange.

So I get home.......and let it idle for a little bit. The VGT is around 67%, EBP is 16.5, and MAP is around 0-.1.

I turn the key off for a second or two, turn it right back on.....fires up, instant turbo whistle out of the exhaust, everything seems normal again. The other strange thing that happened is that as soon as I fired it up, all of my PID's on my Torque App said NO DATA...not sure why. I turned the truck off, and back on...then the PID data all came back. I cleared the PCM faults, and I go take it for a ride.....it's all back to normal!! Good boost, great power, the dash boost gauge is working now....perfect! That's the exact same thing it did the other day. Runs like crap, no boost, warm it up really good, turn it off, back on...and it's all back to normal.

I get back to the house.....no codes, everything is fine. I let it idle and EBP is now at 40, 1.0 MAP, 65 VGT, 22.8 IPR, 580 HPOP....everything perfect!!!!

So what the hell happens when I turn the key off for a second?? What's the EBP supposed to be at idle?? Why would it read 15 at idle, and then 40? This is driving me nuts!!

Could it have something to do with me getting it out and running it to heat up the exhaust...and that does something to the EBP sensor to make it start working as soon as I turn the key off and restart the truck?? It's definitely not a leak, it's something electrical.

Ideas?
 

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Discussion Starter #6
I pulled the EBP sensor just now, it was full of junk, I cleaned out the sensor....and ran a line down the tube to the manifold...and blew it out with compressed air.

I guess I will have a better idea in the morning after it's cooled down. If it fires up and I don't hear that turbo whistle out of the exhaust......it's time to drive my car to work in the morning. Thanks again for the help, I really do appreciate it.

The one thing I'm still stumped about is when it's doing it's "low boost" thing.....why am I seeing 10psi boost at wide open throttle according to the SCT X4, but I'm not seeing any boost at all on the dash gauge?


 

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Discussion Starter #7
Well, it fired up this morning just fine....and ran great. Not sure if the problem was the EBP sensor or not. The only other thing I did to it was load up an SCT tune file that turned off the EGR valve.

I guess I will drive it for a few days and see how it does.
 

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Very interesting. Thanks for reporting back. I cleaned my EBP last February when I did injectors. It definitely had a lot of carbon in it.
 

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Discussion Starter #9
I figured that the problem was either the dirty EBP sensor.....or the fact that I'm now running the SCT with the EGR valve turned off. After a week of running it with no issues, I'm going to go back to the stock tune and see what it does.

If it acts up again on the stock tune, I'm going to assume that it's something with the egr valve....or the SCT tunes just makes the PCM not as sensitive to sensor issues.

I sure hope this problem is fixed....keeping my fingers crossed.
 

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Discussion Starter #10
***UPDATE***


Well....I ran the truck all week long, every day I drove it to work and all around town. No issues...ran perfect, no fault codes....ran perfect!! This was all after cleaning the EBP sensor...AND running on a canned SCT street tune with the EGR turned off.

So tonight after I get home from work I figured I would switch back to the stock tune just to see what happened. Well, it fired right up and seemed to run good....but when I scanned for fault codes....I'm back to getting the PO299 low boost fault.

So now I'm stumped.....what would it run fine on a tune, but throw a P0299 code on the stock tune? I'm guessing that tomorrow morning when I fire it up, it's going to have that low boost issues again.

So what does the stock tune monitor that the SCT tunes don't? This is very frustrating!!

One thing I did notice is that with the SCT tune, it always idles at 85% VGT...I'm assuming that's to get the turbo whine sound out of the exhaust. When I went back to the stock tune, it stayed on 15% for a long time, then started doing it's sweeping thing.

At this point....I don't even know where to start. Ideas??
 

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Discussion Starter #11
One other thing I just got while running the stock tune was a "low exhaust back pressure" fault. I think tomorrow I'm going to replace the EBP sensor....just to take that out of the equation.
 

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One other thing I just got while running the stock tune was a "low exhaust back pressure" fault. I think tomorrow I'm going to replace the EBP sensor....just to take that out of the equation.
I had a similar problem and a buddy suggested that I weld my EGR Valve shut. You have to be careful not to let the bead protrude beyond the circumference of the valve to ensure a stock fitment. Not sure why it would have made a difference on a truck with a delete but it did.

Just a thought.
 

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Discussion Starter #13
I had a similar problem and a buddy suggested that I weld my EGR Valve shut. You have to be careful not to let the bead protrude beyond the circumference of the valve to ensure a stock fitment. Not sure why it would have made a difference on a truck with a delete but it did.

Just a thought.
I guess one way to prove it's an EGR issue is to run the STC tune, and leave the EGR valve turned ON.....if it gives me codes, then I know for a fact it's EGR related.
 

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I had a similar problem and a buddy suggested that I weld my EGR Valve shut. You have to be careful not to let the bead protrude beyond the circumference of the valve to ensure a stock fitment. Not sure why it would have made a difference on a truck with a delete but it did.

Just a thought.
I guess one way to prove it's an EGR issue is to run the STC tune, and leave the EGR valve turned ON.....if it gives me codes, then I know for a fact it's EGR related.
I'm interested to learn how this works out. Good luck.
 
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