Howdy everyone.

I have a MCS 2007 and the car won't boost.

Have fitted a new replacement turbo as the old one seemed bad. So that means the turbo is ok, the wastegate actuator is ok and the blow-off valve is ok... they are all parts of the turbocharger assembly and have all been replaced as a complete new unit.

Obviously, since I've had the turbo off I have checked the cat isn't blocked and all those silly little things.

The BMW diagnostics machine shows no faults. Occassionally, the yellow engine light will come on and connecting up the computer will show a fault describing lower than normal boost pressure... hence original decision to replace turbocharger.

I'm thinking of changing the component called the 'pressure converter' which is the servo device attached to the hose that controls the wastegate. I'm imagining that this device is broken and I hope to solve the problem this way.

Anyone else have any ideas of what might be up with my car?

 

Did you ever find a solution to this? We have a similar problem, started recently and its intermittent but seems to be happening more and more often lately. At random, it will start producing little or no boost and the exhaust note seems to become slightly deeper around the same time. It can last for as little as 15 or 20 seconds or up to a few minutes but usually will come back. I've seen threads on the "superknock" issue and it sounded like a possibilty but im not sure.

 

your problem is completely related to the unichip. get rid of it and you won't have any more problems.

 

I am having this problem as well.

Car starts and runs fine for 3-4 minutes then punch it an all boost is lost. Car is fully stock no modifications of any kind to the engine or turbo.

This is not realy safe but i tried ti to assist figuring what could be wrong. Did this on empty stretch of high way.

1. start car run car on city streets until warmed up have boost and can keep it if i keep RPMs below 3k

2. get on high way and first full throttle get to about 3k and all boost just goes away.

3. Still cruising at 65 miles per hour and turn engine OFF and restart while moving. Boost is bad fr a minute or two even if RPMs go above 3k

4. Then all of a sudden hit 3K again and all boost is lost.

This can be reproduced over an over again.

Does anyone have any ideas? The dealer and a couple of other shops have no idea what is wrong.

Thanks in advance for any help you can provide.