2011 LML sudden loss of power, no dtc's, has DPF delete, she delete, unknown custo

So let me start by saying I haven't been on since January 24 2012!!! Been busy. I no longer work for a dealer. I now work for an independent that specialize in diesel trucks (GM, Dodge, ford). I need help myself now. I have this LML that has a sudden loss.of power under load. Fuel restriction gauge barely made 10 inches when it failed. When all is good it will climb to 15 inches restriction with no issues (may need an AIRDOG installed). There are no Dtcs at all. I smoke checked the induction system and found nothing. I did replace the MAF sensor with an AC Delco because the air filter was not sealing properly and the sensor was covered in a fine dust that would not clean off. Turbo has full sweep. Makes 200 MPA fuel.pressure when all.is good. Pulled FRP #1 On pump and found no metal debris on screen of regulator. MAF grams per second exceeds 400 under load. Jas a 4 inch exhaust that appears to be MBRP. Dude bought truck used from a used truck and it came to him deleted and that is why I have no idea who made the tune. I am an experienced DMAX Tech. I have no clue where to go with this. I have a feeling the custom tune has caused the ECM to not be as sensitive to the drivabiloty issue. Any help here will be great. ☺☺☺

That's tough, not knowing the origin of the tune. It's likely you are not seeing codes because they are ignored. Almost anything that saps power should set a code, as you know. It could also be defueling by default, written into the tune, for whatever reason. With everything deleted, you can't use a stock calibration, because it will limp right out of the gate. You'll have to identify the program, or source another that matches the hardware. It may be a custom hack that won't line up with anything. I've seen a couple of those, and you have to start over, every time. Maybe JK can help. Good luck!

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Originally Posted by DmaxMaverick

That's tough, not knowing the origin of the tune. It's likely you are not seeing codes because they are ignored. Almost anything that saps power should set a code, as you know. It could also be defueling by default, written into the tune, for whatever reason. With everything deleted, you can't use a stock calibration, because it will limp right out of the gate. You'll have to identify the program, or source another that matches the hardware. It may be a custom hack that won't line up with anything. I've seen a couple of those, and you have to start over, every time. Maybe JK can help. Good luck!

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So I can tell you the truck was bought an an auction and likely came out of Canada with the delete already done. I guess they can do that in Canada "Eh?" I'm using a Snap-on Modis Ultra scanner since I no longer work at a GMC Dealer so some data parameters are different compared to the GM Tech2 as is the case with After market scanners unfortunately. Like the Modis shows data for boost pressure but as I recall there is no data parameter in the Tech2 actual boost pressure and like I said, the e fine runs great until it doesn't. I drove it for about 20 minutes yesterday with no issue. Let it set while I went to lunch and then rw-deove and it set almost immediately and I could repeat it but don't see why it's doing it. ARG!!!! This shouldn't be that difficult.

You might look at startup temps (air, fuel and ECT), sensor stability, and diags, then again when up to indicated operating temp. Deletes require most startup diags to be ignored, so it may be somewhere there. Temp sensor (PCM) fluctuations can cause fueling issues, as well as cylinder balance and timing mode variations. I think you'll need to identify the mode(s) while the issue is occurring. It could be a simple as a flaky ECT sensor or a periodic diag cycle delay.

Yeah, I don't know. Notgi g seems out of place as far as data goes. I have wiggle test harness and checked over known chafe points too. The MAP sensor harness on top of intake is connected but one of the wires has a 90 degree bend like the wire is broken and yet I can't make the sensor value fluctuate while flexing the harness. This is what sucks about unknown tunes. Plug and play modules are much easier to diagnose (Edge, Banks, Etc). I really appreciate this brain storming. Never had to deal.with this stuff at a GMC Dealer.

I think DMax is right. You need to get this back to complete stock programming wise. If that means changing some hardware back, so be it. I think you need to start from a known baseline.

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Originally Posted by DieselDavy

I think DMax is right. You need to get this back to complete stock programming wise. If that means changing some hardware back, so be it. I think you need to start from a known baseline.

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Well unfortunately that isn't going to happen. DPF, DOC and all associated sensors have been removed. I believe the DEF tank is still there. EGR bypass valve and EGR valve are unplugged. I don't think he's going to want to pay for all that expensive stuff to be installed. I did discover something though..... It appears that there use to be an axillary fuel tank mounted in the bed of the truck like a tool box fuel.tank. I know those get pretty dirty on the inside. I may be pulling the tank to check for any tank sock restriction plus I can check to see if the fuel tank fuel.line is collapsing.

Making the client pay for all that expensive stuff to be installed may well end up much cheaper than the fine you could be liable for for knowingly helping him keep EPA mandated stuff off his rig. Hell, I couldn't get a local shop to put a pipe on my truck in place of the cat. That would've saved me some scratch but could've cost him something around $25k.
I know, a completely unhelpful post but something for you to consider anyway.

Pulled tank and found tank has slime on it like algae. Disassembled and cleaned out fuel tank sander assembly. Looking into a good diesel fuel algicide. Fuel was clean and clear. O don't have access to a fuel API tester at this time unfortunately. Customer said he just changed the filter and it visually looks new. It's an AC Delco filter. I will keep you posted

FPPF Killem

Better tuning of known quality ;)