Archived Getting desperate at this point. 6.7 no boost, odd symptoms

[ToddMcMilian]

Yesterday I posted the following under the normal 6.7 drivetrain forum and didn't get any ideas, truck is still down and everything I have come up with has not been the issue it appears.

Today on the way home after about 130 miles of driving and thankfully only about 2 miles from home, my truck lost its mind. I had just topped a hill and it pulled fine, nothing out of normal and as I coasted to a stop sign, I noticed all the sudden it was making much more exhaust noise, surging and when I checked my Edge insite, I had zero boost. I left the stop sign and it never made boost until I gave it a little extra and it made a whooping 1 lb and returned to zero. It was not smoking and other than losing power and being noisy, it let us get home and didn't strand us. No codes present when I ran codes. I checked all the pressure boots and didnt feel a hole or find anything loose. My son said he noticed it smoked a bit each time I started it, just normal black smoke and it didnt continue...just a puff when it fired up. There is no sound of spooling unless I give it a quick blip on the throttle and then its barely noticeable. Turbo was replaced about a month ago since vanes were hanging up, so its same as new.

I thought I smoked the turbo but from what I am gathering, I should be seeing it really smoking heavily, esp on my drive home and that is not the case, its just abnormally loud and semi gutless. I checked rail pressure and I have 4.8 at idle, 5.2 at 1000 and 7.4 at 1600 rpm.

Truck is an 08 6.7 fully deleted, with efilive. I removed my edge and cp5 switch to make sure for some reason one of those hadn't gone nuts...no change.

Thanks for any help you can provide!

Update after today's testing. I called the shop that did my turbo and he was certain it was a blown boost tube or boot etc. I decided maybe I missed something when I checked it yesterday so tonight I went out to shop and rigged up a way to pressurize the system and there were no leaks to be found anywhere. I did notice that my Edge CTS that I use strictly for monitoring was showing 5 lbs of boost with the truck at idle....yesterday it was zero. I did some research tonight again and some reading made it sound possible the MAPP sensor could be the culprit so I cleaned it, no luck with that either. I am not getting any codes other than when I started the truck with the temp sensors unplugged on the air box. I fired the truck with the airbox off and the turbo is spinning and it made enough boost to blow the boot off we hadn't clamped down yet so I am at a total loss as to what the hell is going on.
Symptoms are still the same:
No boost shows on CTS most times, at times it shows 5lbs and one time it did that with key on and engine off LOL...
Truck sounds like poop and has a surge at times
Cycling exhaust brake doesn't do anything
Checked all sensor connections and all are tight
Cleaned Mapp with no changes
No CEL codes being generated once I hook sensors up and clear codes
Most times there is no turbo noise when normally the turbo sings pretty well even at idle
Fuel rail pressures seem to be where they should be and increase with engine speed.

I am kinda leaning towards putting a MAPP sensor on it just based on all the posts I read where folks didnt get a code yet but replacing the MAPP cured issues where they had no boost. I just hate throwing parts at this as a guess. I can take it to the shop that did the turbo however he is a long ways from me so tow bill will be quite awful so if I can fix this myself, the world will be a better place, esp the world my wallet lives in.

Thanks for any help gang, I can sure use it!

 

[petersonj]

I know very little about the 6.7 liter engine, but I was wondering ... is it possible that the variable geometry part of the turbo is stuck in the almost closed position? This could account for hardly any boost and the turbo being loud while providing little boost. I note that you just had the turbo replaced, but that doesn't necessarily eliminate it from being the problem.

- John

 

[p-Bar]

Agree with peterson the soot build up could be clogging the turbo . I saw a TSB on cleaning the turbo

 

[ToddMcMilian]

I really think it is the turbo...something along the lines of the vanes being hung up. I am hoping a friend of mine can come thru with a scan tool that is capable of reading the vane positions and cycling them. That would help me pin it down better and give the mechanic a decent starting point so I don't get a lot of diagnostic hours chewed up. It should all be warranty but I wanted to pursue anything I could before I have it towed to him. 2 days of carpooling with the wife and I am semi homicidal lol. I did replace my MAP sensor tonight as a shot in the dark mostly because when I first got the truck the sensor was clogged badly and my cleaning process was a little rough on it, didn't seem to hurt it at the time but I figure worse case I may get a tiny boost in mileage. I also checked the MAS sensor and cleaned it as well. Now I wait and see if we can get our hands on this good scan tool to maybe pin that turbo down better.

 

[ToddMcMilian]

It could be, Im not sure if it would be sooty enough with only being a few weeks old but it may be a bad turbo. Hopefully I can learn a little more about it tomorrow with a scan tool that can cycle the vanes and also perform some position readings.

 

[ToddMcMilian]

Myself and a buddy of mine are kinda leaning towards this, he is sharper than I am on the failing turbo issues and he fells pretty strongly the vanes have stuck in a position where its dumping to the exhaust basically, my exhaust noise is much MUCH louder since this issue happened so I am thinking his theory is probably solid. Hes gonna try and borrow a good scan tool that can cycle the turbo so that might help.

 

[bigblock_doc]

Turbo. Mine sounded like a bunch of nuts and bolts rattling around on acceleration.