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JCarrero 10-01-2012 09:46 AM

2008 335i engine malfunction
Hello guys. I'm new to the forum. Hope everyone is doing great.
I have a 2008 335i for a while. It has 73K miles in it but is in great shape. Hoever once in a while and not under any given condition the engine lights comes on. I've taken it to various BMW mechanics and they can't find the source. They plug in the scanner to check for codes and the only message that comes in the scanner is " Boost Deactrivation "failure". No assign codes reflcted. Engine looses power but does not stall. It keeps running. Then you stop, turn the car of for a couple of seconds and continues to run normal for days and perhaps weeks. It comes on during any type of driving. Accelerating, running steady at 55 mlies. There is not a specific pattern.
No one seems to find what it is. Anyone having a similar issue??


AndrewZ 10-01-2012 06:54 PM

Welcome to bimmerfest!

DSXMachina 10-01-2012 07:17 PM

Hey J, bienvenidos a Bimmerfest! It sounds like you are taking your car to mechanics who work on BMWs, and not BMW dealership mechanics, right? There is a lot of information, called proprietary information, which the average mechanic cannot access without a special scanner. Your engine computer stores a lot of clues about what is happening at the same instant that a CEL (check engine light) is set. Getting at those clues will help determine the cause of the problem.

Here is what I think is going on. Your turbos are capable of making a lot more boost than is safe to use. At a given boost level a sensor triggers a solenoid which sends vacuum to a device which bleeds off the extra boost. There is something wrong in that process and as soon as the computer senses it it cuts off the boost to save the engine from damage. That's why your engine loses power.

Every time you start your car the computer checks to see if there is a problem in that circuit. If no problem is detected it allows your turbo to work like it is designed to work. Your engine then runs OK until the glitch is detected again.

So what is causing the glitch? Well that's what good mechanics get paid to find out. No way any of us can do that for you. (Unless I head back to Rincon again in the near future, but not likely!)

Leekay07 10-01-2012 07:20 PM

Take it to BMW and tell them the wastegate is failing and you would like it fixed before it distroys your turbos and costs them more money. Also keep alog of this because when your turbos do fail you can say its premature and was due to this event.

The wastegate allows the exhaust gas bypass the turbo when you lift off the gas pedal.

JCarrero 10-05-2012 11:24 AM

2008 335i engine malfunction
Thanks a lot pal for the advice. Will certainly have the mechanic look at the wastegate and see what might be wrong.

Thanks again. Will let you know the outcome.

best Regards,


CALWATERBOY 10-05-2012 12:17 PM

1 Attachment(s)

Originally Posted by JCarrero (Post 7115865)
Thanks a lot pal for the advice. Will certainly have the mechanic look at the wastegate and see what might be wrong.

Wastegate might need simple adjustment. But, rear turbo easier said than done....

About those codes, DSX not often wrong. When you get someone who has, say, a Bavarian Technics cable to read proprietary BMW codes, please list 'em here along w/resolution!

Attachment 344448

fun2drive 10-06-2012 01:32 PM

Also take it to them when it happens and don't shut it off so they can pull it before it clears shutting off which seems to be what is happening.
I know that is a pain but it is a bigger pain to take to them when nothing shows...

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