Help! Feels like no boost in just first gear

[SuchFinessse]

Hey guys, I have a 2011 135i (DCT) and within the last 6 or so months, the car has been feeling significantly down on power, and it even fluctuates to the point where I’m second guessing myself.

Back in Feb, I came back from a trip and remember ripping my car on the way back from the airport and it feeling amazing; no sign of the power loss. Then, over the course of 2 months, it progressively got worse. The car was unresponsive, jerky, and down on power all through the rev range.

At first, reflashing the tcu solved a bunch of the clunkiness and unresponsiveness for a while, but it still didn’t feel right, so I explored the possibility of it being the turbo. While exploring that, I decided to get my o2 sensors replaced, since that was a code I was pulling, and it did wonders for responsiveness. That shut me up for a while, but still, something was off. From there, I replaced spark plugs and was convinced up until a few days ago that my power problems were solved. Now I’m not so convinced…

It almost feels like i blew another o2 sensor but I just dont think that’s it. The car is pretty much fine, other than it making 0 boost in first 90% of the time. It will occasionally make a fraction of the boost it used to in first but otherwise, it’s pretty much no boost and relatively useless for accelerating quickly. In fact, I just shift to second at no more than 2k rpm and then pound it from second on because there’s no point. If you floor it in first, it usually feels like the car is struggling.

I should mention the car is and has been MHD stage 2+ the last 50k miles. This car used to burn tires 1st-3rd and now, it’ll only do that 2nd-3rd. Weird! I should also say, it feels like it makes about 80% of the power it used to at the high end, but it isn’t able to hold that power as high in the revs as it used to. If the torque was starting to fall off at 5500 before, its 4500 now, but the power is down for sure as well.

Now I’m back to thinking this is turbo related. Maybe even a gunky manifold? I could easily get a used stock turbo with around 50k miles for around 250-300 which doesn’t seem bad. My car is at 135k still going strong (besides the above). But it just doesn’t feel the same.

What do you guys think? Any suggestions/help are welcome and greatly appreciated!

[mkeiser]

DISA valve?

[________]

Originally Posted by mkeiser

DISA valve?

N55s don’t have variable intake.

[iminhell1]

Datalog. Prove to yourself it's doing what you think it is.
And really everyone should be pulling a datalog a month just for records and to spot trends before they become problems.

If things are pointing to combustion quality I would look and see if it could use a carbon cleaning. I don't think the N55 is as bad as my N54. But it's not immune from it.

[dnhve]

Originally Posted by Onesie

N55s don’t have variable intake.

Yes that's true , you are right