Background:
Bought a 2008 MCS with 55k on it about 1 and a half months ago. Replaced the stock intake with a DOS about a week after getting it and 2 weeks ago changed out the inter-cooler "muffler" with a straight pipe.

Where the problem arose:
The car has been driving great the past week and later in the week (Getting closer to the weekend) I started noticing it being just slightly wonky on the shifting. Then yesterday I drove it in the morning and it was fine (Around 11am, Ambient temps around 85 degrees). Later in the day (about 2 hours later) I had a quick drive to the store, on the way there it seemed to struggle a bit to obtain boost, got to the store got what I needed and then upon restarting the car the Yellow Engine Power Loss light illuminated in my tach and i had NO boost at all. (Ambient temps of just over 90 degrees). Got home hooked the car up to both OBD II readers that I have and neither show any codes at all stored in the ECU. Both readers have been verified to before to be able to read codes so I dont think the car is actually throwing any codes. Jacked the car up in my garage, checked for slipping on the intercooler muffler pipe and it was fine, intake is fine, turbo hoses look good, oil looks fine, coolant is at the min line when engine is cold but i dont believe that to be the problem. Im stumped, after reading for hours online Im basically thinking its either the Thermostat (which IDK if that can cause complete power loss) or what I think is more likely, the boost pressure sensor. What are you thoughts guys? Im at a loss here.

(Im going to be gone for a week this coming Tuesday so the earliest appointment i could schedule with MINI is for next Wednesday)

 

Bump

 

The issue might be a standard OBDII reader cannot see the code. It could very well be proprietary. If the CEL is active on the dash, it's definitely broadcast SOMETHING over OBDII. I was going to say check all the air piping, but you already did that. It's hard to recommend anything without knowing what the CEL is b1tching about.

 

Another thing to try, even though you have OBDII readers of your own, is to see if the local auto shop has a scan tool you could use. It might be a more up to date one that has updated codes that BMW uses.

 

This may be completely incorrect but have you checked the diverter valve on the car? Sometimes the O-ring or diaphram can bust which could mean that you a losing boost...the ECU might read that as a problem, throw a code, and send your car into limp mode. I had a resistor fail on my Alta diverter last week and I received the same symptoms as you are getting. I replaced the resistor, cleared the code and now the car is running fine. I don't know if the thermostat would give you a 'limp mode' issue like this, but I haven't had any issues with my thermostat so I couldn't agree or disagree with your thoughts on that. I'm leaning towards the boost port having issues between the two options you have layed out.

Have you tried clearing the code and driving with caution to see if the error happens again? To me this sounds like an electrical issue not a mechanical issue, but I have heard of the stock diverter valve ripping its diaphram...even at less that 50k miles.

 

Thanks for the replies guys. As i mentioned I have used 2 different OBD readers, both having worked before with my mini but maybe its a different type of code. I just find it hard to believe a $300 OBD reader couldnt pick it up but oh well.

As for taking it to a shop or trying to find out what the code actually is, Im not at home until late Tuesday night and I have an appointment set up with the dealer on Wednesday in the early morning.

As for the diverter valve it could be that, I didnt check it before I left and that would make the most sense as to why its in limp mode and isnt giving any boost at all. I honestly hope its a simple as that. Im going to die if this cost more than a couple hundred to fix. Thanks for the input guys!

If anyone else has any questions/comments/ideas about my problem feel free to ask and Ill get back to you quick, Ive been on vacation for a week and its been bugging me the whole time :/

 

apparently there are 2 kinds of codes. Not all readers can read the more BMW propietary ones (from what I've been reading).

 

I would check the muffler delete connection again. A friend has boost issues when he had his intercooler installed and we could hear a air leak on WOT, I'm not sure ifthatsbthe same case here but like I said, I would check your piping....

 

Just an update guys.

Took my car into the dealer early yesterday morning. Got a call back today. Apparently my Vacuum pump and reservoir need to be replaced as well as the entire valve cover assembly, quoted around $2k. So much for being simple.