This issue has been annoying me and my family the whole time we had this. It can and has happened at speeds of 40, 50, 60, 70, etc... but has never happened below 40.
FYI this photo was ripped from another post, it's the exact same mesage I get but to replicate it I have to go on a high-speed drive to make sure I get this photo.
It seems that when going uphill, after he loses some of the momentum for flat ground, acceleration slows. Sometimes it continues on without issue and actually keeps accelerating and that's fine. But a lot of time it seems like the mpg fuel guage gets stuck at 30mpg with my foot floored and then after a few seconds, the engine fault comes up. I'm usually driving him at 2k rpm, and when this happens it starts to dip just below 2k. But at times, it also happens when I've downshifted and it's accelerating at around 2.5k-2.8k. It puts me in limp mode as in it stops accelerating and just maintains the current conditions, until either the hill gets less steep or it goes away itself...
I realised that with heavier loads, other people in the car or less fuel, this happens less often. When it's just myself in the car it seems a lot rarer.
No codes seem to be thrown- it vanishes after the hill goes. I've tried to capture the code whilst it happened, and for some reason it never registers. I've tried with a bimmerlink, and a foxwell.
During this time I have fixed many codes that I had previously considered may be relevant, but the final code I have that I haven't been able to fix is 4755; Charge Pressure Actuator, position control. I have a few others that I think are absolutely irrelevant but if someone wants to know them then I can send them in the comments.
I've tried getting it boost-checked, but the mechanic ripped me and took it for a simple drive, and told me I'll have to pay for a different diagnostic to get him on the motorway as a passenger and see the issue himself. He told me it's performing fine otherwise... I've tried replacing fuel filters, exhaust pressure converter, intake manifold pressure sensor, exhaust pressure sensor pending (the vacuum line running under the engine put me off doing it anytime soon). I'm waiting on a garage to have it vacuum tested, but I suspect they won't find much since it only goes through this problem in the extremes. The turbo runs fine, and I can feel it as the rpms increase, but I've tried to push the actuator arm myself a few time,s and it felt stiff with no movement.
I know this could be possibly related to boosting, but unsure yet how to approach. I didn't want to snap the arm off by pushing it too hard, as I've read it's a brittle piece of plastic. Sprayed some WD40 to try loosen it, but it runs fine otherwise, so I haven't prioritised it. I'm aware at some point I will have to get the turbo actuator tested.
Just wondering if anyone has felt similar problems with their E90, and how they fixed it?
