Normally I find my answers on here by searching, so I have never posted before.

I have a 2009 MINI JCW. The only modifications are a K&N drop in filter and a boost gauge.

I recently had a code 2885 fixed at the dealership. The half power light was on at the time. Initially they blamed my 'after market boost gauge'. After I talked them through how to disable this they (eventually) traced it back to a faulty pressure converter.

Basically after a week and $600 they got the half power light to go away. They also did the timing chain recall and a heat shield recall.

However, the car still drives like it is at half power. I get maybe 3 psi of boost. I used a Bavarian Tec to scan for codes, but nothing comes up.

So far I have tried switching out the pressure temperature sensor (I had one in the garage), and using an Alta diverter valve. The Alta got me up to 5 psi of boost. Before all of this happened I would see 17 psi.

Does anyone know what could cause loss of boost without tripping codes from any of the sensors?

 

Sometimes it is quite hard to actually trigger the 2885 code. You can drive around for days with low boost and low power before the code comes on.

I had the exact problem you have on my JCW, and took a long time to diagnose. Eventually it turned out that it was a melted / blocked cat on the downpipe. A failing turbo that cannot make enough boost can cause similar symptoms.

 

Thanks, that gives me a place to start.

 

I got it fixed, although I am not exactly sure how.

I put a scope in though the O2 sensor hole. The cat looked pristine. The exhaust side of the turbo looked good as well. Waste gate seemed to operate as it should.

Took the intake manifold off & replaced all rubber hoses that had anything to do with the boost control. Cleaned up the valves since I had the manifold off. They did not look all that bad.

Basically I just cleaned up stuff and reassembled it. Reset the computer and took it for a test drive. It builds boost like it used to.

Nothing really jumped out as being "the issue" though. Maybe I just did a better job of putting it back together than the dealer did.

 

Congrats!

Probably you had a small boost leak in one of the joins in the hoses, and pulling it apart and putting it back together again fixed it.