A newer service bulletin to address low speed throttle response
I had already had the two service bulletins performed posted above. The B12 update fixed the throttle fluctuation on cold start. The B24 update was ineffective. As a result of my correspondence with BMW customer care, below, my 2011 35i is now @ Gault BMW being updated with a very new SW release that is supposed to finally correct the low speed throttle problems. I don't know the version # of that newest service bulletin. BMW customer service was very responsive in my case and spent quite a bit of time with my dealer's service rep. We'll see if it works and I will update this thread when I get my car back.
"Ref: VIN: 5UXWX7C52BL735326, Production #3654460, Miles appx:11,600
Dear BMW Customer Relations:
My wife and I love many aspects of our 2011 X3 35i. We had an absolute blast at the Performance Center Delivery in the Fall of 2011!
There is a significant, persistent issue that has not been resolved to our satisfaction, despite 2 service appointments. Throttle behavior at low speed is unpredictable and erratic to a degree that it keeps me on edge. My wife now looks for reasons to not drive the car. It is very difficult for either of us to perform gentle throttle manipulations at low speed without the car either momentarily hesitating or shooting off like a rocket. Likewise, when slowing down and then resuming posted speeds in situations like a traffic light transitioning from red to green, there is a similar difficulty predicting what will result from gentle throttle inputs. In other scenarios, the engine is a marvelous and velvety smooth beast.
Back in April 2012, we had the following update performed at Gault BMW in Endicott NY:
“A new software calibration was just released for this engine:
SIB 24 02 12
N52T/N55 with 8HP45: Delay in Engine Response
F25 with either N52T or N55 engines and 8HP45 transmission up to 1/16/2012
When slowing down to lower suburban road speeds and then reaccelerating, a delay in engine response may be experienced
Unfavorable EGS and DME software calibration
Program the vehicle using ISTA/P 2.46.0 or higher”
After the above visit, one behavior I didn’t mention above was totally resolved: an RPM surge on cold start…esp with the A/C on. I think that problem was associated with a different service bulletin. So that’s the good part. We continued, however, to experience the erratic throttle behaviors I described above. I noticed an additional behavior as well. On a cold start during the summer months (our first summer with the car), if you don’t wait for the RPMs to stabilize and if you attempt to drive away, the engine can stall. It has done this on two occasions, requiring a restart. I work around the irritation by waiting about 15 seconds for the RPMs to settle down before driving off. Again, this problem may have existed since day one and I may have just noticed it during our first summer.
In October, we took the car back to Gault BMW. The friendly service staff and technicians could not find any codes and confirmed the SW update was correctly performed back in April. Again, they were very professional and supportive, but were unable to solve the problem. We’ve been Acura customers since the mid-1990’s and decided to give BMW a try last year. There is so much to love about our X3, but this problem is a definite sore spot. We would greatly appreciate if BMW would get to the root cause of this problem.