Stalling and stumbling

[aspenx5]

I have a 2013 X5 (twin turbo) with 25,000 miles on it. I live at high altitude, in Aspen, CO and my car is not kept in a garage.

On cold starts it stalls (sometimes more than once) either while turning at low speeds or while reversing in a straight line. After the stalling it stumbles really bad the first minute or so, then it drives fine the rest of the day. When it acts up it feels like the fuel doesn't reach the engine, however, I don't get any lights on the dash or any error messages.

I've taken it to BMW in Boulder several times. The first time they reset the idle, which didn't make any difference. Another time they didn't do anything other than run some tests but they could't find anything wrong with it, it stalled on them only once in three weeks. It's now back there and this time it's acting up on them every day, and they are still running tests (this is week two). So far they've replaced the spark plugs.

Does anybody know if there is a setting that needs to be adjusted for high altitude? Or for cold weather? (it does misbehave more often when the temperature is lower)

I'm driving an X4 with 5000 miles and same engine as mine and it stumbles just as bad as mine when I start it in the morning. Aside from annoying it's embarrassing and dangerous. Any ideas?

[pragueX5]

what about th fuel?? water in the fuel? using the same petrol station all the time???
given you sayits happenng on the rental car as well I would try to think out of thr box (car) what other variables can influence this..... eg fuel, wild animal damaging eiring in thr rnginr compartment etc etc

[MichiganMike]

The altitude at Aspen (7900 feet) is almost 2500 feet higher than the dealer in Boulder, Colorado. If your starting problems are related to altitude this may be more apparent at the higher altitude in Aspen.

Even a turbo engine makes slightly less power at higher altitudes particularly when spinning at lower RPM as occurs at start-up and idle where turbo boost is minimal. A cold gas engine also generally requires more fuel than a warm engine to operate smoothly. In addition, lower octane fuels are typically sold at higher altitudes where engine knocking is less of a problem, but this lower octane may cause the engine management system at start-up to retard spark more affecting operation.

I am wondering if this combination of factors together with constraints in the engine control system to control pollution are combining to make your engine prone to stumble during a cold start at altitude until it warms up a little. The engine management system may be having difficulty balancing the challenging parameters. A change in fuel or a fuel system additive like Techron may be worth trying.

If the fuel injectors or emission controls are not working properly, the fuel filter could use replacement or there are carbon deposits on the valves, these may be additional contributing factors. Your engine during a cold start may be particularly sensitive to any or all of these issues due to the altitude.

[BMW-GT]

I had the same problem with the cold start, stumbling the first minute or so. My dealer replaced all my fuel injectors under warranty.

http://f10.5post.com/forums/showthread.php?t=1074012

I'm not sure which engine you have. Mine is the 8 cylinder.

[aspenx5]

I go to different gas stations, around here and in Denver/Boulder where I'm often on weekends. Shell is my first choice if it's handy but sometimes I use Conoco or Valero, never the cheaper ones. And I always get Premium gas.

Today I had a very interesting talk with a client who has had the same issues with other brands. An Audi and a Subaru, both turbo. According to him the problem is the turbo at high altitude, it just doesn't perform the way it's supposed to. That explains why my rental is behaving the same way as my car, it has the exact same engine. He told me that the fuel filter into turbo needs extra care, to check the turbo inlet filter annually and also the ignition coil. I called the dealer and mentioned this and I was told that "BMWs are engineered different than other brands". So, instead, they are replacing my fuel pump and fuel pump's controller. I'll keep my fingers crossed...

Originally Posted by pragueX5

what about th fuel?? water in the fuel? using the same petrol station all the time???
given you sayits happenng on the rental car as well I would try to think out of thr box (car) what other variables can influence this..... eg fuel, wild animal damaging eiring in thr rnginr compartment etc etc

[42pilot]

I put my money on one of the "critical" sensors, like manifold air pressure, or even the fuel injector control module. The MAP sensor works off 5v source meaning between 0 and 5 volts, it must provide a range of pressure from ambient (14.7 psi at sea level) to full boost (for arguments sake, let's say 28 psi). If the sensor is not providing the correct pressure measurement just because its not calibrated, the engine will never run correctly and will fail at certain times - early cold morning, high altitudes, hot starts, etc. And diagnostics will never find a flawed sensor. It has to be removed and measured against a known source.

The fuel injector control module is less likely, but it needs a certain voltage to fire the injectors. If the voltage fluctuates for whatever the reason (like the additional voltage needed for a start, or when you turn on the rear window defogger), you can get the engine to stumble, but this should fire the Check Engine Light and throw a code. Without the code, you'll never diagnose this one either.

Since these motors are turbo charged (with VGT technology) and they have over 170 sensors, you will never run out of air. I fly a lot of airplanes with turbo chargers that are much less sophisticated and I can take these as high as 20,000 ft. Granted the size of the compressors and turbines are different from your car, but 7,000 or 9,000 ft is not problem for our engines. The ECU simply turns up the VGT because of the MAF sensor telling it, "more air please".

[42pilot]

Originally Posted by aspenx5

I go to different gas stations, around here and in Denver/Boulder where I'm often on weekends. Shell is my first choice if it's handy but sometimes I use Conoco or Valero, never the cheaper ones. And I always get Premium gas.

Today I had a very interesting talk with a client who has had the same issues with other brands. An Audi and a Subaru, both turbo. According to him the problem is the turbo at high altitude, it just doesn't perform the way it's supposed to. That explains why my rental is behaving the same way as my car, it has the exact same engine. He told me that the fuel filter into turbo needs extra care, to check the turbo inlet filter annually and also the ignition coil. I called the dealer and mentioned this and I was told that "BMWs are engineered different than other brands". So, instead, they are replacing my fuel pump and fuel pump's controller. I'll keep my fingers crossed...

Fuel filter into turbo? Run from this person or at least disregard what they told you.

The turbo inlet filter is the cold air intake - period. The intake filter will not make your car fail like what you are describing.

And depending on your engine, you'll either have 8 coils or 6 coils. It's possible one coil could be failing but diagnostics can find this easily.