LB7: Not building boost, Fuel Issue, Injector issue?? PLEASE HELP

[bhollehday]

My truck would run fine until 2000 rpm it would run really rough and smoke white. I plugged my ppe in and read the data. My MAF readings were low but still moving fine (25 at idle, where its usually at 35). My boost reading went from 14.7 at idle down to 9psi! And my DES and ACT fuel readings would jump around crazy going up and down which didnt look normal. My Injector pulse widths looked mostly normal. #6 and #2 were the only ones over 1, which i think they were all under 1 before. #6 was at 3 and #2 was at 2.5. And my BARO was normal. I had the issue and went and bought a new fuel filter, 3 hours later put it on and it was running fine again. Next day drove it and it was running fine until the end of the day it started doing it again.

I thought it was a fried turbo or a stuck open wastegate so i pulled that all apart. The turbo impeller has NO play whatsoever. It seems to spin freely and makes no noises. It has a little bit of resistance but feels like its normal (like an new ball bearing). My wastegate diaphram functions fine with pressure from my air compressor.

Would a fuel issue cause the turbo to not build boost? Or an leaky/bad injector?? I could drive the truck around with this issue, but the minute i rev it past 2K rpm it would stumble and smoke white. It seemed like it would only stumble when im trying to boost or request fuel. I have a PPE tune on it, would it be worth putting the truck back to stock?

I need to figure this out asap. Will have to start riding the train to work tomorrow

 

[Yngdmax92]

What's the truck? Have you checked the normal rub through areas of the intercooler pipes?

 

[CaptPhil]

If it ran fine with a new fuel filter then started acting up again I am thinking a bad batch of fuel. Change the filter again.

Sent from my SM-G900V using Tapatalk

 

[WolfLMM]

Ok so, it's a LB7 right?. Fuel pressure bouncing around screams bad fpr to me.

 

[bhollehday]

Wow im subscribed to this thread but didnt get any emails! I thought someone would ahve replied by now!

Im leaning towards an FPR as well. IC pipes are fine. Im pretty confident its not a boost leak. Bad fuel cant be right either, because it runs fine mostly, and then all of the sudden its like something happens and it runs bad until I turn the truck off and let it cool down.

The truck seems to idle fine, maybe has a real light lope to it sometimes barely noticeable. Ive never had the issue before, never thrown a code pertaining to fuel. Im afraid to drive it, even though it currently seems to run fine. I dont want to make a problem bigger than it has to be. Someone said to test the FPR by removing the harness to it, and if my pressure runs max then it works, if not that could be the issue. Is the FPR accessible though without removing parts?

Im also wondering if it would be worth just putting a new CP3 on it since it come with a new $140 FPR. I found the CP3 w/FPR for $530 OTD. Ive got a 160K miles on the truck, do CP3's go out a lot at this mileage?

 

[bhollehday]

Heres a little update..

After troubleshooting the truck some more I tried everything and couldn't get it to change what its doing. On the computer end, my boost sensor kept reading low values (But my turbo would spool hard and consistent when running good), my MAF readings were low (New MAF, clean, no leaks), and I just couldn't make that change. Finally I pulled out the boost sensor and put a buddys sensor in, and BAM it started running good again. So I went and bought a boost sensor from autozone and everything would run fine, until about 10 minutes after startup and same thing

Now my interior lights are also stuck on. The radio turns off with the door opening, all doors are shut. Yet while driving they never turn off. After turning the truck off they turn off after about 15 minutes luckily. But this is starting to smell like an ECM or electrical issue. My next step is going to be replacing the ECM with another used one.

I realized later that this problem first came about after I tried using a BARO sensor as the BOOST sensor. I bought a new BARO sensor in hopes to get the EGR system back working, and thought this truck had 3 BARO sensors, one for ATM, one for boost, and one for EGR. Turns out the BOOST sensor has the same harness and mount, but the ECM is looking for a different voltage value than the BARO or EGR BARO. Anyways I got a boost reading of 27 PSI at idle when I swapped them and an overboost code. So I immediatly switched them back. After that for about 50 miles everything seemed fine. Then I had the issue. I tried a new sensor now to no avail and it isn't as intermittent as a shorted wire, so Im really thinking ECM is to blame here. I really cant imagine swapping those sensors doing ANY harm though??

 

[WolfLMM]

I don't think swapping the sensors harmed anything.

I would check the condition of all soft fuel lines. When they are cold they are stiff and will not suck shut very easily, has the truck warms up these lines will become soft and it's possible they are sucking shut, thus causing the low boost and poor running.

Just my 2 cents

 

[bhollehday]

I don't think swapping the sensors harmed anything.

I would check the condition of all soft fuel lines. When they are cold they are stiff and will not suck shut very easily, has the truck warms up these lines will become soft and it's possible they are sucking shut, thus causing the low boost and poor running.

Just my 2 cents

Thats a good point I like your thinking. But if you consider the conditions when troubleshooting it in person, It just doesn't feel fuel related. If that was the case you could ease into it with a light load and kind of bounce off of the point where it pinches and the rough running and smoke wouldn't be so consistent. But easing into it or just smashing it does the same all the time everytime. (Injectors and CP3 checked out and good btw)

It just seems too consistent to be an issue of that nature. If that was the case, then I dont imagine it would run equally as bad at the exact same RPM's. Plus when I rev my engine at idle and monitor the boost reading, it goes from atm, DOWN. There is no situation I can think of that would allow the intake tube to build a vacuum instead of a pressure! Besides a faulty wire, sensor, or ECM.

Plus its a little too much of a coincidence that my dome lights are stuck on in between all of this. I touched nothing inside when this happened.

Some other things that are odd that could be related to my ECM...

I had it re-flashed with the latest software few months back, and doing that made my INFO display on the speedo black out. I couldn't see whether I was in drive or park. Then after driving it for a couple days before taking it back to see if another reflash would fix the issue, it just magically turned on and has stayed on. Also my AC seems to turn on when I have the AC button off and the re-circulation button on. But it doesn't do that consistently. Sometime with recirc on its turns on, and then you turn off and back on and the AC isn't running anymore.

 

[bhollehday]

I don't think swapping the sensors harmed anything.

I would check the condition of all soft fuel lines. When they are cold they are stiff and will not suck shut very easily, has the truck warms up these lines will become soft and it's possible they are sucking shut, thus causing the low boost and poor running.

Just my 2 cents

Check out this guys issue. Similar conditions to mine...

http://www.duramaxforum.com/forum/0...-no-smoke-no-more-money-help.html#post9432681

The turbo is still what Im thinking the problem is, however after inspecting it, I just had to rule it out!