Sticking EGR valve?
6.4L, SCT with DPF-off tune, no power increase or anything. Just dpf-free with straight pipe. Been running for around 5 years like this with no issue, no reflashes, everything has been perfect!
A couple of days ago while trying to accelerate in overdrive (enough pedal to ask for power, not enough to downshift) it started to buck / not enough power and white then black smoke came out... and it got through it. (the smoke changed to black as it was starting to provide power finally). At the next light, from a standstill, it had NO power with tons of white, then black smoke... kept on it... smoke went from white to black, and it took off... smoke cleared and launched forward like normal... The next day, went for a drive, and took off a couple of times, WOT. Everything seemed totally normal at operating temp.
Today, driving to work, still in the development, cold... light throttle (10-30%ish), NO power, tons of white smoke. Tried this a couple of times going through the neighborhood. Pulled over and let it warm up some more. Idled a little rough and not steady, cycled up and down by a hundred rpms or so in a rhythm.
Put it back in drive and tried to drive after this brief warmup... same issue, smoke, not going anywhere... pushed a little farther, the engine sound changed instantly and at that moment, the power was back after the smoke changed to black, then cleared. As it warmed up, it seemed to do it less but there is still an issue.
The strangest part is the engine sound. Grainy sound of the normal diesel engine... when it's doing this, it sounds very muffled and quiet... then when it changes, it goes back to a real / normal diesel sound, and GOES.
Does this sound like an EGR valve sticking open? The engine sound changing so obviously makes me think so.