X5 50i weird issue when accelerating

[flipnkraut]

My wife's X5 50i started having weird issues when giving it more than ¼ - 1/2 throttle. It cycles from surging to no power and will keep doing that until you let off the gas. It accelerates fine if you don't try to give it more than ¼ throttle.

Any idea what could be wrong? Also anyone in the Austin area have a good indy shop they recommend?

[RED_Y_]

Transfer case may be?
https://f15.bimmerpost.com/forums/sh....php?t=1493534
Spark plugs and coils?
https://f15.bimmerpost.com/forums/sh....php?t=1540381
Check engine light is on?

[1norseman]

Did you get any "drive train malfunction" or other error?
When did you last change: coils, spark plugs, crankcase vent line?
How many miles on those items?

[flipnkraut]

Originally Posted by 1norseman

Did you get any "drive train malfunction" or other error?
When did you last change: coils, spark plugs, crankcase vent line?
How many miles on those items?

No errors

Coils spark plugs last year ~12k miles
Crankcase vent line... never? We bought it used 2 years ago so no idea if it's ever been changed.

[turboawd]

Sorta sounds like you're not building boost in the turbo. I'd check vacuum lines to turbo wastegate.
Also check your intake piping for cracks. Someone just recently posted where his intake pipes just broke apart. They're plastic.

[vastano]

If you’re able to check it with ISTA that may help even if there are no check engine lights. I’m battling this same issue but I THINK I may have fixed it. First I changed the Transfer case fluid which definitely helped but I still had the issue. Then I went to the dealer because my crankcase vent lines were cracked so they were replaced under extended warranty. The problem remained.

Lastly the 2 times I had checked the errors with ISTA it pointed to a bad MAF sensor so I just changed them both out. It’s been a few days since I’ve done this and no stuttering/hesitation. I’m at ~50k btw.