x15 cold idle boost fluctuation.

[marek4792]

2019 X15 Performance 430k miles, EGR tuneup at 410k miles. So when starting the truck for the first time, it will idle with steady boost in its SCR warmup mode (not demandated) and about a few minutes in the turbo will start boosting up and down 2-3 pounds whistling on and off until bumped into hi-idle, engine rpm is steady the whole time and doesn't surge at all.
Just wondering if this a normal thing I'm overthinking or do I got something tweaking out besides the nut behind the wheel.

[tree98]

Maybe the VG ring is starting to wear and not holding position well?? Did you monitor with insite to see if the ECM is commanding it up and down? 430k miles on a non demandated turbo is probably close to a full life.

[marek4792]

Thanks! I'll look into that, just changed out the speed sensor in the turbo recently because it crapped out and after that I guess I just noticed the fluctuation. Still also got to check the mechanical side for air/exhaust leaks that aren't so obvious before I fire off the parts cannon at this thing.

[Rawze]

It is most likely the EGR pressure sensor not seeing the right pressure when its cold and air is still dense. It is likely not an issue unless it gets excessive.. to which the EGR circuits need cleaning out including the Delta-p block and maybe even the egr cooler itself if it gets dirty enough.

ref: http://rawze.com/forums/showthread.php?t...8#pid22458

[marek4792]

Just got a chance to look into it, Turbo is being commanded when this happens, nothing out of place on the datalog either. Like Rawze was saying I'll monitor for now until it gets rampant.

[marek4792]

Just an update, I believe I may have found the smoking gun in the form of a failed exhaust gasket right after the bellow pipe pre-aftertreatment. The clamp is blackened in spots and few small streaks on the pipe, but you'd have to really looking for it to see it. It makes sense if some backpressure is getting out.

[Rawze]

(12-06-2022 )marek4792 Wrote:  Just an update, I believe I may have found the smoking gun in the form of a failed exhaust gasket right after the bellow pipe pre-aftertreatment. The clamp is blackened in spots and few small streaks on the pipe, but you'd have to really looking for it to see it. It makes sense if some backpressure is getting out.

Prostars have a very similar common issue. Seems a lot of them, the back-side connection for the flex.pipe behind the turbo has a split in it to make it easier to install.. but if someone does not get it slipped down onto the next pipe far enough.. that split will make a hole and leak exhaust, cause regen issues, and make the truck driver sleepy all the time due to exhaust fumes seeping into the cab. Sometimes they are like this even from factory.