Engine Malfunction...UGH!

[rangerfan94]

So my 2013 E93 DCT suffered the dreaded Engine Malfunction problem on Friday afternoon. The car was towed and was delivered to Greenwich BMW service before 5pm on Friday.

I was getting on the Merritt Parkway driving from Stamford CT towards Greenwich and got the ENGINE MALFUNCTION / REDUCED POWER alert, and the car eventually died on a very small incline. I restarted the engine, and was able to get the car moving again, which is good, because the car stopped in a construction zone with no shoulder on either side, and high enough barriers on the right side that there was no way for me to get out of the car. I then had a SERVICE ENGINE SOON light on, and I had a few INCREASED EMMISSIONS alerts as well.

Long story short, it wasn't until roughly 30 minutes ago that I finally got an email from my SA with the diagnosis. I need some help from the experts. Is this a likely possible scenario?

"We will be replacing the brake booster pressure sensor on your vehicle as per BMW. We do not feel this can cause a stall issue but it is the only code found in the computer system. My shop foreman would like to road test the vehicle overnight to make sure there is no more drivability issues after the sensor is installed. Would this be okay?"

My repsonse: "Are you sure it’s not the 1) throttle actuators, 2) oxygen or fuel pressure sensors, 3) idle control valve, or 4) the ignition coil?"

His response: "There are no faults or current issues with any of those parts mentioned. Just the booster sensor. Can we drive it overnight and see if anything else malfunctions?"

I told them to keep the car as long as they want. I don't want to drive it until I am sure this won't happen again. The car died in a dangerous spot, and I'm in no rush to experience that again. Any help or advice is greatly appreciated.

[tinman831]

If the code says there's a brake booster problem then fix it? Those other parts usually throw specific codes.

[Beemdog]

Difficult to imagine how a power brake booster sensor could cause the engine to die (other than just horrible engine management software).

The OP is right to question the dealer's diagnosis, but I don't know that I'd give them unlimited rights to drive the car around, either. Tough situation. While it is not suprising to enter a reduced power mode for a variety of faults, having the engine die would seem to indicate something more essential has failed than a brake booster sensor.

[Ezio]

typical dealership fixing the wrong part. It has happen to me before also. the problem is that no matter what you say, they have to see the problem happen before then can fix it.

[WCH]

I had the same experience. The dealer replaced the brake booster and the car was completely fine afterwards. I still don't understand the connection between drivetrain malfunction and the brake booster but it was the right diagnosis in my car. Hope this fixes yours as well.

[s85e90]

Because the brake booster is vacuum actuated so yes if it failed it will cause issues with the engine. This also seems to be a common replacement item.

[Beemdog]

Originally Posted by s85e90

Because the brake booster is vacuum actuated so yes if it failed it will cause issues with the engine. This also seems to be a common replacement item.

I can see a large vacuum leak at the power brake booster causing a rough idle and possibly causing the engine to die as a result. However, replacing just the sensor for the brake booster might be incorrect if it is in fact the vacuum brake booster itself that is bad. Seems hard to believe the sensor itself could cause a vacuum leak large enough to kill the engine, but if the leak is larger than 1/4" it might.

[///M Power-Belgium]

Originally Posted by Beemdog

I can see a large vacuum leak at the power brake booster causing a rough idle and possibly causing the engine to die as a result. However, replacing just the sensor for the brake booster might be incorrect if it is in fact the vacuum brake booster itself that is bad. Seems hard to believe the sensor itself could cause a vacuum leak large enough to kill the engine, but if the leak is larger than 1/4" it might.

When brake booster is nok ,maybe this can cause also malfunction of the brakes !
In this case maybe it's meant to cut the motor power , and avoiding to drive the car without brakes , that's why i'm thinking maybe it's a programmed safety measure , but i'm not sure about this !

[Beemdog]

Reducing power is one thing, cutting the motor completely is considered an unsafe procedure due to stranding motorists in instersections, freeways, and other hostile situations. Conditions that cause the engine to die unexpectedly often result in safety recalls.

[///M Power-Belgium]

Originally Posted by Beemdog

Reducing power is one thing, cutting the motor completely is considered an unsafe procedure due to stranding motorists in instersections, freeways, and other hostile situations. Conditions that cause the engine to die unexpectedly often result in safety recalls.

Agreed and not agreed ,because driving at high speeds and without brakes is maybe even more dangerous .

[Beemdog]

The brakes should still work without a vacuum power booster, although with less authority.

[jphughan]

I had the exact same thing happen except for the all-out stalls, and replacing the brake booster sensor resolved the issue. The diagnosis was that brake fluid had spilled onto the sensor, which ruined it. You'll be happy to know that BMW, conscious of the sensor's susceptibility to brake fluid, decided to locate this sensor....directly under the brake fluid reservoir. So the dealer said that either they or an indy shop I use overfilled the reservoir during a flush and some excess fluid was ejected from the reservoir under hard driving (I do go to the track) or some may have just spilled during the service itself. Whatever the cause, it was covered under warranty and I never saw another engine malfunction warning after the sensor was replaced.

As for your car actually stalling, I remember my car had practically zero power when the engine malfunction warning came up, so I guess I could see it not having enough power to get up an incline, though I'm still a bit surprised given that you say it was a very small incline and even happened a second time. What gear were you in on the incline?

Also, just out of curiosity, how do barriers only on the right side of a road prevent you from being able to get out of the car?

[rangerfan94]

Thanks for the feedback.

Originally Posted by jphughan

Also, just out of curiosity, how do barriers only on the right side of a road prevent you from being able to get out of the car?

So Google "Merritt Parkway images" and take a look at the photos. Imagine a 2 lane parkway with no shoulder at all on the left, and a very small shoulder at some points on the right. And then imagine a construction project that shifts the lanes a foot or two to the left because the crews have installed miles of concrete barriers on the right side, inside of the white line, making the road (dangerously) narrow.

Then imagine your M3 stopping on an incline in the right lane with a barrier at most 1 foot from passenger door, higher than the top of the window on the M3. Exit via the passenger window was not possible, and the left lane traffic was buzzing by at 60+mph, making it impossible to get out via the driver's door. There was no was out of that car without all traffic stopping.

[soniczoom5]

i think i had the same issue; see below

http://www.m3post.com/forums/showthread.php?t=973309

[rangerfan94]

Originally Posted by soniczoom5

i think i had the same issue; see below

Have you had any issues since they fixed the car?

[soniczoom5]

Originally Posted by rangerfan94

Have you had any issues since they fixed the car?

nope - zero issues since they fixed it

[fuddman]

I just got the same light and my dealer is also telling me the brake (something or other) failed.
Someone on this thread mentioned this problem may come from spilling brake fluid onto a brake booster sensor, possibly during a brake flush. Guess what? The dealer just flushed my brake fluid about two weeks ago. Hmmmm.
OP, how did your fix come out?

[WCH]

That's interesting. I had my brakes flushed about 2 weeks before my incident as well. After the fix, the car was fine.

[Flying Ace]

chilling....just horrible sensor location.